Energetics of northern phocid seals

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Title:
Energetics of northern phocid seals the influence of seasonality on food intake and energy expenditure
Physical Description:
xi, 107 leaves : ill. ; 29 cm.
Language:
English
Creator:
Ochoa-Acuna, Hugo, 1962-
Publication Date:

Subjects

Subjects / Keywords:
Harp seal -- Food   ( lcsh )
Harbor seal -- Food   ( lcsh )
Ringed seal -- Food   ( lcsh )
Zoology thesis, Ph.D   ( lcsh )
Dissertations, Academic -- Zoology -- UF   ( lcsh )
Genre:
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by Hugo Ochoa-Acuna
Thesis:
Thesis (Ph.D.)--University of Florida, 1999.
Bibliography:
Includes bibliographical references (leaves 97-106).
General Note:
Typescript.
General Note:
Vita.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030478435
oclc - 42638246
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AA00022337:00001

Table of Contents
    Title Page
        Page i
    Acknowledgement
        Page ii
    Table of Contents
        Page iii
        Page iv
    List of Tables
        Page v
    List of Figures
        Page vi
        Page vii
        Page viii
        Page ix
    Abstract
        Page x
        Page xi
    Chapter 1. Introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
    Chapter 2. Seasonal changes in body mass and feeding rates of northern phocid seals
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
    Chapter 3. Basal rates of metabolism of phocid seals
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
    Chapter 4. Seasonal changes in basal rates of metabolism of harp seals
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
    Chapter 5. Influence of body composition on seasonal changes of energy expenditure of captive harp seals
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
    Chapter 6. Activity levels and energetic cost of activity in harp seals
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
    Chapter 7. Synthesis and conclusions
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
    References
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
    Biographical sketch
        Page 107
        Page 108
        Page 109
Full Text













ENERGETICS OF NORTHERN PHOCID SEALS: THE INFLUENCE OF SEASONALITY
ON FOOD INTAKE AND ENERGY EXPENDITURE






















By

HUGO OCHOA-ACUNA


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA


1999
















ACKNOWLEDGMENTS


I would like to acknowledge the staff of the seal lab, Grant

Dalton, Jason Noseworthy, and several volunteers at the Ocean

Sciences Centre, Memorial University of Newfoundland, for their

constant help, support, and good humor despite the hard work and

weather. I would particularly recognize the assistance and

friendship of Elizabeth Noseworthy, who provided invaluable

insight on the husbandry needs and psychology of the seals.

I am very grateful and pleased that working on this project

allowed me to meet and befriend Ted Miller, a source of

inspiration on how to transform research into science and grind

into fun. I would like to acknowledge also the permanent support

of my advisor, Brian McNab, throughout this study.
















TABLE OF CONTENTS
page


ACKNOWLEDGMENTS ................................................ ii

LIST OF TABLES .................................................. v

LIST OF FIGURES ................................................ vi

ABSTRACT ........................................................ x

1 INTRODUCTION .................................................. 1

Natural History of Pinnipeds ............................... 1
Systematics ............................................. 1
General Biology ......................................... 2
Ringed, Harp, and Harbor Seals .......................... 3
Metabolic Rates of Pinnipeds ............................... 4
Energy Budgets of Pinnipeds ............................. 4
The Influence of Body Size and Composition on
Metabolic Rates of Phocid Seals ...................... 9
Objectives of the Present Study ........................... 10

2 SEASONAL CHANGES IN BODY MASS AND FEEDING RATES OF
NORTHERN PHOCID SEALS ...................................... 14

Introduction .............................................. 14
Material and Methods ...................................... 15
Statistical Analyses ................................... 15
Body mass and food intake annual cycles .............. 15
Changes in maintenance energy requirements ........... 16
Relationship between body mass and food
requirements ...................................... 17
Results ................................................... 17
Seasonal Differences ................................... 17
Harp seals ............................................ 17
Harbor seals .......................................... 18
Ringed seals .......................................... 19
Influence of Photoperiod ............................... 20
Discussion ................................................ 20

3 BASAL RATES OF METABOLISM OF PHOCID SEALS .................... 44

Introduction .............................................. 44
Material and Methods ....................................... 45


iii










Results ................................................... 47
Discussion ................................................ 49

4 SEASONAL CHANGES IN BASAL RATES OF METABOLISM OF HARP
SEALS ...................................................... 58

Introduction .............................................. 58
Material and Methods ...................................... 59
Results ................................................... 60
Discussion ................................................ 61

5 INFLUENCE OF BODY COMPOSITION ON SEASONAL CHANGES OF
ENERGY EXPENDITURE OF CAPTIVE HARP SEALS ................... 70

Introduction .............................................. 70
Material and Methods ...................................... 71
Laboratory Analyses .................................... 72
Calculations ........................................... 72
Results ................................................... 73
Discussion ................................................ 74

6 ACTIVITY LEVELS AND ENERGETIC COST OF ACTIVITY IN HARP
SEALS ...................................................... 80

Introduction .............................................. 80
Material and Methods ...................................... 81
Results ................................................... 82
Discussion ................................................ 83

7 SYNTHESIS AND CONCLUSIONS .................................... 91

Basal Rates of Metabolism of Phocid Seals ................. 91
What Causes the Seasonal Changes in Energy Expenditure
of Captive Harp Seals? ................................. 92
Implications for Modeling Energy Consumption in Wild
Populations of Pinnipeds ................................ 93

REFERENCES ..................................................... 97

BIOGRAPHICAL SKETCH ........................................... 107
















LIST OF TABLES


Table page

2.2. Periods (seasons) among which years were divided in
relation to daylength observed in Logy Bay,
Newfoundland (4738'N, 52'40'W) ....................... 25
2.3. Seasonal changes in body mass, energy intake, and
requirements of captive phocid seals. Means from
each seal used in these calculations were
previously weighted by the number of observations
taken from each individual ............................ 26
2.4. Yule-Walker probability values for the
autocorrelation-corrected regression of daily
energy intake (MJ/day) against date, daylength,
temperature ('C), and average solar radiation
(MJ/m2) for 16 northern phocid seals held captive
at the Ocean Science Centre, Logy Bay,
Newfoundland (47'38'N, 52'40'W) ....................... 27

3.1. Total (V02) and mass-specific (Vo2/Mb) resting
metabolic rates of individual harp Pagophilus
groenlandicus, harbor Phoca vitulina, and ringed
P. hispida seals ...................................... 53
4.1. Results of the analysis of variance, ANOVA (F
statistic, F and probability value, P) used to

test the influence of season on total (V02) and

mass-specific (V02/Mb) basal metabolic rates of
three adult male harp seals, Pagophilus
groenlandicus ......................................... 64

4.2. Comparison of total (V02) and mass-specific (V02/Mb)
basal metabolic rates among seasons for three
adult harp seals, Pagophilus groenlandicus. Cells
containing the "less than" sign (<) indicate that
the first season represented in the column header
had significantly lower values than the second
season .. .............................................. 65
5.1. Body composition of adult harp seals throughout the
year cycle. The amount of each of the different
components is given in absolute (kg) and relative
terms (percentage, in parentheses) .................... 75
















LIST OF FIGURES


Figure page

1.1. Breeding grounds ("Gulf" and "Front", dotted areas),
and approximate migration routes of northwest
Atlantic harp seals (Pagophilus groenlandicus).
Approximate dates in which seals stay in the two
extreme locations are also provided ................... 13
2.1. Body mass record of female harp seal (Pagophilus
groenlandicus) BAB kept outdoors in Logy Bay,
Newfoundland (47038'N, 52040'W) ....................... 28
2.2. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay,
Newfoundland (47'38'N, 52'40'W). a) female CHE; b)
male ELM .. ............................................ 29
2.3. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay,
Newfoundland (4738'N, 52'40'W). a) male JAM; b)
male MIC .. ............................................ 30
2.4. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay,
Newfoundland (4738'N, 52040'W). a) female RHO; b)
male TYL .. ............................................ 31
2.5. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay,
Newfoundland (4738'N, 52'40'W). a) male VIC; b)
male VIR .. ............................................ 32
2.6. Body mass records of harbor seals (Phoca vitulina)
kept outdoors in Logy Bay, Newfoundland (47138'N,
52'40'W). a) male CAE; b) male CLA .................... 33
2.7. Body mass records of harbor seals (Phoca vitulina)
kept outdoors in Logy Bay, Newfoundland (4738'N,
52040'W). a) male DAR; b) male JUL .................... 34
2.8. Body mass records of harbor seals (Phoca vitulina)
kept outdoors in Logy Bay, Newfoundland (4738'N,
52'40'W). a) female KEV; b) male OSC ................. 35
2.9. Body mass records of ringed seals (Phoca hispida)
kept outdoors in Logy Bay, Newfoundland (4738'N,
52040'W). a) male LER; b) female MEG .................. 36
2.10. Seasonal changes in body mass (kg) observed in seven
adult harp seals (Pagophilus groenlandicus, Pg);
six harbor seals (Phoca vitulina, Pv); and two
ringed seals (Phoca hispida, Ph). Animals were
fed ad libitum and held outdoors at the Ocean










Sciences Centre, Logy Bay, Newfoundland (47038'N,
52040'W) .............................................. 37
2.11. Seasonal changes in digestible energy intake (DEI,
MJ/day) observed in seven adult harp seals
(Pagophilus groenlandicus, Pg); six harbor seals
(Phoca vitulina, Pv); and two ringed seals (Phoca
hispida, Ph). Animals were fed ad libitum and
held outdoors at the Ocean Sciences Centre, Logy
Bay, Newfoundland (47038'N, 52'40'W) .................. 38
2.12. Seasonal changes in maintenance energy requirements
(MER, MJ/day) observed in seven adult harp seals
(Pagophilus groenlandicus, Pg); six harbor seals
(Phoca vitulina, Pv); and two ringed seals (Phoca
hispida, Ph). Animals were fed ad libitum and
held outdoors at the Ocean Sciences Centre, Logy
Bay, Newfoundland (4738'N, 5240'W) .................. 39
2.13. Relationship between photoperiod and food intake of
adult harp seals (Pagophilus groenlandicus) kept
outdoors at the Ocean Sciences Centre, Logy Bay,
Newfoundland (47038'N, 52040'W) ....................... 40
2.14. Relationship between photoperiod and food intake of
adult harbor seals (Phoca vitulina) kept outdoors
at the Ocean Sciences Centre, Logy Bay,
Newfoundland (47038'N, 52040'W) ....................... 41
2.15. Relationship between photoperiod and food intake of
adult ringed seals (Phoca hispida) kept outdoors
at the Ocean Sciences Centre, Logy Bay,
Newfoundland (47038'N, 52040'W) ....................... 42
2.16. Photoperiods experienced by captive harp seals
(Pagophilus groenlandicus) kept at the Ocean
Sciences Centre (OSC), Logy Bay, Newfoundland
(47038'N, 52040'W), and that hypothesized for harp
seals in the wild during their annual migration ....... 43
3.1. Metabolic chamber used in measuring oxygen
consumption of phocid seals in air. A
temperature-controlled water bath controlled the
temperature of a glycol solution circulated
through a series of four radiators placed in a
special funnel inside the chamber. Air was forced
through these radiators to control the chamber
temperature ........................................... 54
3.2. Relationship between resting oxygen consumption rate
and ambient (air) temperature for three adult male
harp seals (Pagophilus groenlandicus) ................. 55
3.3. Oxygen consumption rates under basal conditions of
six harp seals (Pagophilus groenlandicus), three
harbor seals (Phoca vitulina), and one ring seal
(P. hispida) in relation to their body mass ........... 56
3.4. Body temperature of three adult male harp seals
(Pagophilus groenlandicus) in relation to ambient
(air) temperature ..................................... 57










4.1. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the
adult male harp seal, Pagophilus groenlandicus,
ELM .. ................................................. 66
4.2. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the
adult male harp seal, Pagophilus groenlandicus,
TYL ................................................... 67
4.3. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the
adult male harp seal, Pagophilus groenlandicus,
VIR ................................................... 68
4.4. Seasonal variation in mass-specific basal rates of
oxygen consumption for three adult male harp seals
(Pagophilus groenlandicus) ............................ 69
5.1. Methodology used to estimate concentration of
deuterium oxide at time of administration (CO).
This method avoids the overestimation of total
body water that occurs when the concentration
determined from the first blood sample is used as
an estimation of CO ................................... 76
5.2. Relationship between body mass and absolute amount of
body fat (top graph), and proportion of body fat
(bottom graph) of four captive adult harp seals
(Pagophilus groenlandicus) ............................ 77
5.3. Seasonal changes in the components of the body and
proportion of body fat of captive adult harp seals
(Pagophilus groenlandicus) ............................ 78
5.4. Seasonal changes in body composition and energy
content of captive adult harp seals (Pagophilus
groenlandicus) .. ...................................... 79
6.1. Diagram of a phocid seal swimming. These animals use
lateral altenating movements of their hind
flippers and posterior part of the body to produce
thrust. The location of the activity recorder
used to detect lateral strokes is marked by the
shaded circle ......................................... 86
6.2. Activity levels of nine harp seals, Pagophilus
groenlandicus, measured as tilts per minute in
relation to time of day ............................... 87
6.3. Changes in activity levels of captive harp seals,
Pagophilus groenlandicus, measured as tilts per
minute in relation to season .......................... 88
6.4. Influence of activity on daily mass change of captive
harp seals, Pagophilus groenlandicus. The plot
represents the relationship between an estimator
of energy spent in locomotion [(tilts/min)l.42]
and the residuals of the linear model relating
daily mass change (DMC,g) and the variables
"seal", "season", mass (g), energy intake
(kJ/day), and time spent on deck (%) .................. 89


viii










6.5. Relationship between the frequency of lateral strokes
of the posterior part of the body and hind
flippers, and swimming speed of phocid seals.
Data from harp seals (Pagophilus groenlandicus,
Pg) and ringed seals (Phoca hispida, Ph) from Fish
et al. (1988); data from harbor seals (Phoca
vitulina, Pv) from Davis et al. (1985) ................ 90
7.1. Basal rates of metabolism (relative to values
predicted by body mass using Kleiber's 1961
relationship) and levels of activity measured as
tilts per minute ...................................... 94
7.2. Basal rates of metabolism of several species of
phocid seals obtained from this study and from
published reports. Halichoerus grypus, Hg (Fedak
and Anderson 1982, Boily and Lavigne 1995);
Leptonychotes weddelli, Lw (Kooyman et al. 1973,
Castellini et al. 1992); Phoca hispida, Ph
(Parsons 1977); P. largha, P1 (Ashwell-Erickson
and Elsner 1981); P. vitulina, Pv (Matsuura and
Whittow 1973, Davis et al. 1985); Pagophilus
groenlandicus, Pg (Gallivan and Ronald 1979,
Renouf and Gales 1994). K represents the
relationship calculated from Kleiber (1961), W
represents the relationship calculated from McNab
(1988) ................................................ 95
7.3. Changes in components of the energy budget of captive
harp seals (Pagophilus groenlandicus) throughout
the annual cycle ...................................... 96
















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

ENERGETICS OF NORTHERN PHOCID SEALS: THE INFLUENCE OF SEASONALITY
ON FOOD INTAKE AND ENERGY EXPENDITURE

By

Hugo Ochoa-Acufta

August 1999

Chairman: Brian K. McNab
Major Department: Zoology

As in many other mammals, rates of food intake of phocid

seals (Family Phocidae) vary throughout the year. Information on

seasonal variability of feeding rates and energetics of northern

phocid seals is important because of the controversy surrounding

metabolic rates of marine mammals and because effective fisheries

management requires models of fish consumption by seal populations

that explicitly include temporal variation. I studied energetics

over in three phocids, the harp (Pagophilus groenlandicus), harbor

(Phoca vitulina), and ringed (P. hispida) seals. I analyzed

records of food intake and body mass of captive seals. I

determined weekly body mass changes, food intake, and activity

levels for seven harp, six harbor, and two ringed seals. In

addition, I measured basal metabolic rates of five harp, three

harbor, and one ringed seals through open-flow respirometry.

Oxygen consumption was measured from post-absorptive animals at










different ambient temperatures for periods of 2-4 hours. Some

determinations were made throughout the year, but most (10-18 per

month) were made in October, January, April, and July on three

male harp seals, to determine seasonal changes in basal rates of

metabolism. I also established the body composition of four adult

harp seals during the four seasons of the year, to determine

changes in the energetic equivalency of changes in body mass.

Activity levels were monitored using modified Mk6 time-depth

recorders, to establish if activity was an important component of

the energy budget.

Captive seals undergo profound changes in body mass and food

consumption throughout the year, and after accounting for changes

in body mass, feeding rates still differ across seasons, which

suggests shifts in energy expenditure. The species studied have

basal rates of metabolism higher than expected from body mass, but

that did not differ from those of terrestrial flesh-eating

eutherians. I also determined that shifts in basal rates of

metabolism were directly correlated with the observed fluctuations

in energy expenditure and food consumption. I also found that

changes in body mass of harp seals throughout the year were due

not only to changes in the size of body fat stores, but also to

changes in lean body mass. The results indicate that changes on

basal metabolic rates explain a significant portion of the

seasonal variation in energy expenditure, and that these changes

may translate into large changes in the amount of fish consumed by

the northwest Atlantic harp seal herd.
















CHAPTER 1
INTRODUCTION


Natural History of Pinnipeds


Systematics

Pinnipeds (Order Carnivora, families Otariidae, Odobenidae,

and Phocidae) are mammals adapted for living both on land and at

sea. All species give birth over land or ice (King 1983). In

addition, with the exception of the walrus (Odobenus rosmarus),

lactation occurs almost entirely over solid substrate (Oftedal et

al. 1987a).

Until recently there was much debate about whether or not

pinnipeds are poliphyletic. Today, based on morphological and

biochemical data, it is accepted that both groups (phocids on one

hand, and otariids and odobenids on the other) descend from a

common ancestor (Sarich 1969, Arnason and Widegren 1986, Wyss

1988).

There are 33 species of extant pinnipeds grouped in three

recognized families: Odobenidae, consisting solely of the walrus;

Otariidae, consisting of the "eared" seals (fur seals and sea

lions); and Phocidae, or "true" seals. The eighteen recognized

species of phocids are in turn classified into two subfamilies:









Monachinae (Antarctic phocids plus elephant and monk seals), and

Phocinae (northern phocids) (King 1983).



General Biology

Seals are important top predators in many marine ecosystems,

and they are especially abundant in highly productive areas, such

as polar regions and zones of upwelling. Although most seals feed

preferably on nectonic prey such as fish, squid, and krill,

bearded seals (Erignathus barbatus) and the walrus feed primarily

on benthic invertebrates (Bonner 1994).

The young of pinnipeds are born after a 8-10 month gestation

period, and offspring are highly precocial at birth. Female

pinnipeds give birth to a single pup, and reproduction tends to be

highly synchronized, with mating occurring only a few days after

parturition. In otariid species, which always breed on land,

females nurse their young from four to 24 months, whereas in the

mostly ice-breeding phocid species, females suckle their young for

only a few weeks or even days (Oftedal et al. 1987a).

Most phocid mothers stay onshore continuously suckling the

pup until weaning (but see Boness et al. 1994). During lactation,

the mother does not feed and milk production is sustained entirely

from body reserves stored before parturition. On the other hand,

otariid mothers alternate periods of suckling on land with periods

of foraging at sea throughout the more prolonged lactation (Costa

1991).











Ringed, Harp, and Harbor Seals

Ringed seals (Phoca hispida) and harp seals (Pagophilus

groenlandicus) are the most abundant of the northern seals (around

6,000,000 and 4,000,000 individuals, respectively) (Riedman 1990).

Although harbor seals (Phoca vitulina) are one of the most

widespread species of pinnipeds, they are not as abundant

(-400,000).

Harp seals occur in Arctic and subarctic waters of the North

Atlantic Ocean from around 900 E to 900 W (Ronald and Healey

1981). Harp seals migrate north in the summer and south in winter

and spring to breed (Figure 1.1). Harp seals congregate to

reproduce on pack ice, where they form huge concentrations. Harp

seal pups are born from late February to early March, and are

weaned after a 12-day lactation (Bowen and Sergeant 1983). After

breeding, adults molt in April-May and then migrate North.

Ringed seals have a wide distribution in seasonally and

permanently ice-covered waters of the Northern Hemisphere. They

occur through the Arctic basin, and seasonally into the North

Atlantic, Hudson and James Bays, and the Chukchi and Bering Seas.

Ringed seals are non-migratory and use fast-ice for breeding

(Frost and Lowry 1981).

Harbor seals inhabit temperate and subarctic waters of the

North Atlantic and North Pacific. On the northwest Atlantic, they

can be found from Massachusetts to Hudson Bay. Throughout the










year, harbor seals are littoral in distribution and nonmigratory

(Bigg 1981).


Metabolic Rates of Pinnipeds

Some phocid and a few otariid species have been studied

through the development of energy budgets to determine the effect

of these populations on commercially important fish species

(Lavigne et al. 1982, Beddington and de la Mare 1985, Lavigne et

al. 1985, Swartzman and Haar 1985, 0ritsland and Markussen 1990).

A major drawback in estimating food intake of pinnipeds is the

paucity and uneven quality of data on metabolic rates and energy

expenditure.



Energy Budgets of Pinnipeds

The energetic content of food ingested by an homeotherm must

be equal to the sum of energy lost through feces and urine, plus

the sum of energy spent as the specific dynamic action of food,

and the energy used in the various tasks performed (Lavigne et al.

1982). The following equations summarize how energy is

partitioned in a homeotherm:

GE = F + U + ME

ME = SDA + NE

NE = BMR + TR + A + G + R

Where GE = energy content of food; F = fecal losses; U -

urinary losses; ME = metabolizable energy; SDA = specific dynamic

action of food; NE = net energy; BMR = basal rate of metabolism;










TR = temperature regulation; A = activity; G = growth; R =

reproduction.

Fecal and urinary energy losses in pinnipeds have been

measured only on grey and harp seals. When fed Atlantic herring

(Clupea harengus) juveniles from both species lost between 5 -

7.5% of their gross energy intake through feces and 6.9 9.9% of

their metabolizable energy intake through urine (Keiver et al.

1984, Ronald et al. 1984). Fecal and urinary losses of harp seals

were not affected by feeding frequency. However, seals feeding on

herring with low energy content had a greater proportion of the

energy ingested lost through the feces than seals feeding on

herring with high energy content, and this was probably due to the

greater nitrogen content of herring with low energy content.

The increase in metabolic rate caused by the digestion and

assimilation of food is the specific dynamic action (SDA). The

magnitude and duration of the influence of SDA on metabolic rate

has been measured in only one pinniped, the harp seal (Gallivan

and Ronald 1981). The apparent SDA represented around 17% of the

gross energy of the diet, increasing the daily metabolic rate

between 11 21%, depending on the size of the meal. These

authors found that, on a herring diet, metabolic rates did not

return to pre-prandial levels until after 10-12 hours.

Basal rates of metabolism are standardized measures used for

intra- and inter-specific comparisons. Basal metabolism is the

rate of energy expenditure of mature animals at rest, under









thermoneutral conditions, and in a post-absorptive state. The

scarcity of data on pinniped and cetacean basal rates of

metabolism have fueled a long-standing debate on whether basal

rates of marine mammals are comparable to those predicted by the

empirical equation relating basal rates of metabolism and body

mass developed by Kleiber (1961) using data from domesticated

mammals. Historically, it was widely accepted that marine mammals

had basal rates higher than those of terrestrial mammals. This

assumption was supported with empirical data (Irving et al. 1935,

Scholander 1940, Irving and Hart 1957, Hart and Irving 1959,

Kooyman et al. 1973, Miller and Irving 1975, Miller et al. 1976),

and explained as an adaptation for living in cold water (Irving

1969). On the other hand, some researchers have postulated that

pinnipeds do not have higher rates of metabolism when conditions

to determine the basal rates are met (Lavigne et al. 1982, Schmitz

and Lavigne 1984, Lavigne et al. 1986).

Pinnipeds live in many different climates, from the Arctic

and Antarctic to the shores of Australia, and the Hawaiian and the

Galapagos Islands. Temperature regulation is accomplished through

different adaptations in the different pinniped groups. Fur seals

(Genus Arctocephalus and Callorhinus, family Otariidae) are able

to maintain a temperature gradient of 25'C across some 20 mm of

fur (Irving et al. 1962). On the other hand, phocid seals, sea

lions, and the walrus, have a sparse underfur with relatively

little insulative value. These animals have a blubber layer that

has multiple functions: serves as energy reserve, adjusts










buoyancy, streamlines the body, and acts as thermal insulation

(King 1983, Riedman 1990). Studies on ringed seals have shown

that the blubber layer is distributed in such a way that the ratio

of blubber thickness to body radius is nearly constant over the

body, giving maximal insulation with a given amount of blubber.

This agrees with the heat exchange model of a cylinder, in which

heat loss does not depend on the wall thickness per se, but on the

ratio between wall thickness and the radius of the cylinder (Ryg

et al. 1988). Phocid seals use their fat reserves without

compromising their thermal insulation. Using computed tomography,

Nordoy and Blix (1985) demonstrated that, although the blubber

layer provided 94% of the energy used by grey seal (Halichoerus

grypus) pups fasting for 31 days, the subcutaneous blubber

contributed a constant proportional area of the total cross-

sectional area of the body. During fasting, harp seals not only

lose blubber, but also core mass, thus probably maintaining the

ratio between blubber thickness and body radius (Worthy and

Lavigne 1987). Northern elephant seal (Mirounga angustirostris)

pups fasting after weaning also lose body mass, keeping body

composition relatively constant (Rea and Costa 1992).

The cost of swimming has been measured in several pinniped

species. Pinnipeds exhibit a curvilinear rise in metabolic rate

with increasing swimming speed. This is primarily due to the

increase in drag. Despite the effect of drag, pinnipeds use less

energy for locomotion than terrestrial mammals of similar size,

due in part to the absence of postural costs (Feldkamp 1987).










Although phocids and otariids use different means of propulsion

(using their rear flippers and fore flippers, respectively), both

groups have equivalent minimal costs of locomotion. Adult

California sea lions (Zalophus californianus) and harbor seals

have minimum costs of swimming of 2.5 and 2.3 J / kg m,

respectively. These values represent 2.3 and 2.1 times the

metabolic rate measured when resting, respectively (Davis et al.

1985, Feldkamp 1987). During diving, Weddell seals (Leptonychotes

weddelli) have been shown to maintain an almost constant swimming

velocity of about 2.0 2.1 m/s. These animals did not increase

metabolic rate when diving as compared to resting rates

(Castellini et al. 1992). However, these results are complicated

by possible physiological compensations that occur during diving.

The same study found that metabolic rates decreased with an

increase in diving duration.

Growth energetics have been studied extensively in

pinnipeds. Whereas in otariids lactation lasts more than four

months, in phocids the nursing period only lasts from four days to

eight weeks. As in terrestrial mammals, resting metabolic rates

of growing pinnipeds are higher than those measured in adult

animals (Miller and Irving 1975, Lavigne et al. 1986, Markussen et

al. 1990). Phocid seal pups are able to efficiently deposit large

amounts of blubber in very short periods. Northern elephant seal

pups gained 54.9 % of the mass lost by their mothers (Costa et al.

1986).









The energy spent in reproduction has been measured in

pinnipeds taking advantage of the temporal separation between

foraging at sea and reproductive activity on land. In phocids,

females fast during the reproductive period and thus neonatal body

mass and maternal mass loss during lactation are good indicators

of maternal expenditure (Fedak and Anderson 1982). Males of

polygynous species have high levels of expenditure. Southern

elephant seal (Mirounga leonina) bulls lost body mass at a rate of

up to 20 kg per day during their 58-day stay on land, totaling

almost 40% of their original mass (Fedak et al. 1994).



The Influence of Body Size and Composition on Metabolic Rates of
Phocid Seals

The most important factor influencing metabolic rate among

and within species is body mass. Body mass has been shown to

explain a large portion of the variation in basal metabolic rates

among mammals and birds. In adult animals, changes in body mass

are, for the most part, changes in the size of fat stores. Lean

body mass is relatively constant not only in size, but also in

composition.

There is considerable controversy regarding the relative

contribution of adipose tissue to basal rates of metabolism. Many

researchers (e.g., Blaxter 1989, Lavigne et al. 1986) have

proposed that the contribution of adipose tissue to metabolic rate

is insignificant, and that, as a consequence, lean body mass

instead of body mass should be used in allometric equations










relating metabolic rate and the size of the animal. However, some

studies have demonstrated that adipose tissue is highly active and

contributes significantly to the overall heat production

(McCracken and McNiven 1983, McNiven 1984).

Parallel to the annual reproductive and behavioral cycle,

phocid seals experience large seasonal fluctuations in some

physiological characteristics, such as body mass and metabolic

rate. Over a four-year period, body mass of some captive adult

male harp seals increased from September to May and then decreased

from April to August. These fluctuations comprised up to one

third of the peak mass (Miller, personal communication). Annual

fluctuations in body mass are caused by changes in the thickness

of the blubber layer. Here, Renouf and Noseworthy (1991) found an

inverse relationship between water temperature and blubber content

in harbor seals. Unfortunately, data on seasonal variation on

phocid seals is inconclusive. Renouf and Gales (1994) reported a

slight or no increase in body mass of harp seals from May to

February. Nevertheless, these authors reported mass-specific

basal rates of metabolism twice as high in April-July as compared

with values from August-March.


Objectives of the Present Study

The apparent conflict between commercial fisheries and

pinniped populations make it imperative to develop accurate energy

expenditure models for seal species to predict fish consumption.

The large sizes of the populations of ringed, harp, and to a much









lesser extent, harbor seals makes the development of precise

energy budgets of critical importance. A 500-g difference in the

estimated average daily consumption of fish by harp seals

translates to a difference of 730,000 metric tons eaten annually

by this population. This difference might substantially affect

the prediction of the impact of seals on the recovery of Atlantic

cod (Gadus morhua), given that the spawning stock is estimated to

be down to 30 to 50,000 metric tons (Lavigne, personal

communication). Although many studies have addressed the question

of whether seals prey on commercially important species, few

studies have determined basal rates of metabolism, the cost of

thermoregulation both in air and in water, and the influence of

body fat changes on those parameters. Given that food intake,

activity, and body composition of pinnipeds change seasonally, it

is necessary to study metabolic rates throughout the year, to

construct meaningful predictors of fish consumption.

The purpose of this study was to obtain this information for

phocid seals. Research was conducted at the Ocean Sciences Centre

of Memorial University of Newfoundland, using the seals,

installations, and equipment there available. Chapter 2 addresses

the question of the presence and extent of annual cycles of body

mass, food intake, and energy expenditure in harp, harbor, and

ringed seals. Chapter 3 presents the results of the study of

resting metabolic rates in relation to ambient temperature and

age, and the estimation of basal rates of metabolism for the three

species of phocids mentioned above. Metabolic rates of thirteen









seals (nine harp seals, three harbor seals and one ringed seal)

were measured in terms of oxygen consumption in air and in water.

Chapter 4 describes the analysis of seasonal changes in energy

expenditure and basal rates of metabolism of three adult male harp

seals. Chapter 5 analyzes the influence of body composition on

energy expenditure and basal rates of metabolism of adult harp

seals. Chapter 6 presents the results of the study of activity

levels and the cost of activity of captive harp seals. Chapter 7

summarizes the most relevant findings of this study.




















































Figure 1.1. Breeding grounds ("Gulf" and "Front", dotted areas),
and approximate migration routes of northwest Atlantic harp seals
(Pagophilus groenlandicus). Approximate dates in which seals
stay in the two extreme locations are also provided.
















CHAPTER 2
SEASONAL CHANGES IN BODY MASS AND FEEDING RATES OF NORTHERN
PHOCID SEALS


Introduction

Northern phocids live in a highly seasonal environment and,

consequently, some aspects of their life history demonstrate a

high level of circannual periodicity. For example, female harp

seals give birth every year between late February and early March,

and nurse their pups for 10-13 days (Sergeant 1991). During

lactation, phocid females do not forage, although there is some

evidence that harbor seal females perform foraging trips similar

to those of otariid seals (Boness et al. 1994). Although most

phocid males do not defend territories on solid substrate, as do

otariids and phocids belonging to the genera Mirounga and Hydrurga

(elephant and grey seals), they seem to guard females from other

males (Riedman 1990), and as a consequence, they might drastically

decrease food intake during the breeding season.

The objectives were to determine the presence and extent of

seasonal changes in body mass and food intake in three species of

northern phocids. The appropriate data were collected from 1987

to 1997, although the length of the records varied from animal to

animal.









Material and Methods

This study was conducted at the seal facility of the Ocean

Sciences Centre, Memorial University of Newfoundland, in Logy Bay,

Newfoundland (47038'N, 52040'W). Animals were kept outdoors in a

facility consisting of two 12-m-diameter tanks (300-M3 capacity

each) and 190 M2 of haul-out decking surrounding the tanks. All

tanks were cleaned weekly and refilled with seawater pumped from

the bay.

Seals were fed daily around 1200 h. Each animal was allowed

to eat as much as it wanted for a period of two hours. Food

consisted of thawed frozen herring supplemented with vitamins.

I analyzed body mass and food intake records of seven seals

held at the Ocean Science Centre, Logy Bay, Newfoundland, to

explore the influence of seasonality on body mass and food intake

of adult (> 4.0 year-old) harp seals.



Statistical Analyses


Statistical analyses were performed using different

statistical procedures from the STAT and ETS modules of the SAS

statistical package (SAS Institute Inc. 1985). All values

provided are mean standard error, SE.

Body mass and food intake annual cycles


I tested for the presence of annual cycles of body mass and

food intake through time-series regression analysis (PROC AUTOREG)

using daylength as the independent variable. This procedure









produced parameter estimates corrected for the autocorrelation

introduced in the data by sequential sampling of body mass, food

intake, and daylength. Data were previously detrended to remove

ontogenetic changes in body mass and food intake. In addition, I

confirmed the presence of circannual and infrannual cycles of body

mass and food intake using spectral analysis (PROC SPECTRA). This

procedure uses the finite Fourier transform to decompose data

series into a sum of sine and cosine waves, and produce a

periodogram which reflects the contribution of each harmonic to

the total sum of squares (SAS Institute Inc. 1993).

Changes in maintenance energy requirements

I calculated daily mass change (DMC, g/d) as the difference

between two consecutive weighings, divided by the days elapsed

between them. Total food intake during these days was averaged

and multiplied by the energetic content of the herring fed to the

animals (Table 2.1), and by its digestive efficiency (Lawson et

al. 1997) to estimate digestible energy intake, DEI. I included

only those days in which the sole food type offered was herring,

and the seals were completely satiated after the two-hour feeding

period.

Energy intake at constant body mass (maintenance energy

intake, MEI) was calculated through regression analysis (x

intercept of DMC regressed against DEI) for each of the different

periods (i.e., seasons) in which each year was divided (Table

2.2). In addition, I calculated the mean of body mass, DMC, and

DEI for each of these periods.









Relationship between body mass and food requirements


I tested the null hypothesis that MEI of adult seals was not

related to body mass. I regressed mass-specific MEI against body

mass of adult (> 4 years old) seals. I included 'seal' as a

factor in the linear model to account for possible individual

differences.


Results

Body mass of adult harp seals (> 4.0 years old) varied from

a minimum during summer to a maximum during spring, with an

average value of 146.725.9 kg (Table 2.3, Figures 2.1-2.5).

Adult harbor seals had a mean body mass of 87.24.9 kg that varied

from a minimum in the fall to a maximum in summer (Table 2.3,

Figures 2.6-2.8). Body mass of the two ringed seal studied varied

from a minimum during the summer to a maximum in winter, with a

mean of 452.8 kg (Table 2.3, Figure 2.9).



Seasonal Differences


Harp seals


Although 63.7% of the variation in body mass was due to

inter-individual variation, and only 10.2% was due to seasonal

effects, these were highly significant (F3,9o=13.6, P<0.0001)

(Figure 2.10). Individual differences in the rate of daily mass

change were not significant (F7,89 = 0.7, P=0.7), and season

explained most (31.2%) of its variation (F3,s9:14.3, P<0.0001)









Body mass did not have an effect on the rate of mass change

(Fi.9o=3.2, P-0.08).

Food intake varied from a minimum during the fall to a

maximum in winter, with a mean of 32.23.06 MJ/d (Figure 2.11).

Individual seals had similar levels of food intake, and season was

the only significant factor in the model, explaining 29% of the

total variation (F3,89=15.0, P<0.0001).

The analysis of the relationship between daily mass change

and energy intake revealed that harp seals in captivity changed

their level of energy expenditure throughout the year.

Maintenance energy requirements were lowest during fall and

highest during spring, with a mean value of 31.32.96 MJ/d (Figure

2.12). Individual seals had similar maintenance requirements, and

20.4% of the overall variation was due to seasonality (F3,47=5.3,

P<0.0031). Body mass had no effect on maintenance requirements

(F1,47=- 0.1, P=0.81).

Harbor seals


Body mass of harbor seals varied from a maximum in summer to

a minimum during the fall (Figure 2.10). The influence of season

on body mass of harbor seals was highly significant (F3,113=1.3,

P<0.0001) explaining 18.5% of the total variation. Individual

differences were also significant (F5,113=7.7, P<0.0001) and

accounted for 20.9% of the total variation in body mass. Season

also had an effect on the rate of daily mass change (F3,112=1l.9,

P<0.0001) accounting for 23.3% of the total variation, whereas









individual differences and body mass effects were not significant

(F5,112=0.67, P=-0.6274; F1,112=2.1, P=-0.1498, respectively).

Food intake of harbor seals was maximal during the fall,

declining thereafter until summer (Figure 2.11). Season explained

20.6% of the total variation in the rate of feeding (F3,112=11.7,

P<0.0001), and individual differences explained 8.6% (F5,112=2.9,

P<0.02). Body mass had no influence on feeding rates (F1,112=7.7,

P<0.0001).

I found that harbor seals displayed seasonal changes in

their level of energy expenditure (Figure 2.12). Season explained

10.6% of the total variation in maintenance requirements

(F3,46=3.3, P<0.03). Individual differences accounted for 23.7% of

the total variation (F5,46=4.4, P<0.003) whereas body mass effects

were not significant (F1,46=1.8, P=0.1831).

Ringed seals


The two ringed seals studied did not display seasonal

changes in body mass (F3,13=1.0, P=-0.4433) (Figure 2.10).

Individual differences were also not significant (F,,13=2.2,

P=0.1581). The rate of daily mass change was not influenced by

individual differences (1,12=4.1, P=0.0649), season (F3,12=1.6,

P=-0.2492), or body mass (F1,13=1.i, P=0.3242).

Ringed seals had maximal levels of food intake during spring

and minimal during summer (Figure 2.11). Season explained 45.6%

of the total variation in food intake (F3,12=4.7, P<0.03).

Individual differences explained 18.5% of the variation in feeding









rates (F1,12=5.8, P<0.035) and body mass explained 22.5% (F1,12=7.0,

P
I found that energy expenditure of ringed seals was not

influenced by season (F3,3=0.7, P=0.5996), individual differences

(F1,3=0.6, P=0.4794), or body mass (F1,3=2.0, P=0.2535) (Figure

2.12).



Influence of Photoperiod

All the harp seals that were two years old or older and for

whom at least one year of data was available showed an inverse

relationship between daylength and body mass (Table 2.4). Food

intake also increased with decreasing photoperiod during spring

and fall (Figure 2.13). Conversely, only the female harbor seal

(KEV) demonstrated a relationship between photoperiod and body

mass, but food intake was strongly influenced by photoperiod

(Figure 2.14). The two ringed seals included in this study also

showed an inverse relationship between photoperiod and body mass,

although no clear pattern was observed between daylength and food

intake (Figure 2.15).


Discussion

This study demonstrated that harp, harbor, and ringed seals

displayed profound seasonal changes in food intake. Levels of

energy expenditure of harp and harbor seals were also influenced

by seasonality. I did not detect seasonal effects on body mass

and energy expenditure of ringed seals, and this was probably

related to the small sample size (n = 2).









Seasonal changes in body mass have been reported for a

number of pinniped species (Boulva and McLaren 1979, Ashwell

Erickson and Elsner 1981, Fedak and Anderson 1982, Stewart and

Lavigne 1984, Costa et al. 1986, Bowen et al. 1987). The cycles

of body mass have been related to reproduction, with pronounced

mass loss occurring during lactation and rutting, and the annual

moult (Ryg et al. 1990). Changes in body mass do not seem to be

only a consequence of food availability. This and other studies

performed under ad libitum conditions demonstrate that pinnipeds

vary food intake throughout the year, and that the resulting body

mass cycles closely resemble those observed in the wild (Ryg et

al. 1990, Renouf and Noseworthy 1990, Kastelein et al.

1990a,b,c,1991,1995). Lager et al. 1994 found that harp seals

kept at the natural photoperiod observed at 69'N also increased

mass from fall to spring, and that food intake reached a maximum

during winter. These data suggest that the observed variation in

body mass of wild seals cannot be attributed directly to

variations in food availability.

The spatial separation between feeding and breeding grounds,

and the high degree of synchrony of the breeding events may have

favored the development of internal circannual rhythms of food

intake among phocids. Animals tend to have lower levels of energy

expenditure when food consumption is low or null (e.g., Grande et

al. 1958, Felig et al. 1983, Elliot et al. 1989). This metabolic

depression may be explained by the recession of organs involved

with food processing that have a high metabolic intensity (Burrin









et al. 1988, Daan et al. 1989, Burrin et al. 1990, Konarzewski and

Diamond 1995). Thus, phocids may concentrate feeding during only

some periods of the year, and withdraw from food consumption when

food availability is low.

Another factor that may contribute to the development of

annual cycles of food consumption in phocids in particular, and

mammals in general, is the necessity to devote significant amounts

of time to search for mates, defend territories, chase

competitors, and nurse pups during the seasonal and synchronized

breeding events. Renouf et al. (1988) observed a negative

correlation between the number of social interactions and the rate

of food intake in a group of captive harbor seals. Korhonen and

Harri (1986) found that food intake and activity of farmed

polecats (Mustela putorius) varied inversely during the year.

My observations of cyclic anorexia in northern phocids

suggest that they rely on environmental cues, other than food

availability, to regulate food intake. Harp seals decreased food

intake with increasing photoperiod, both during spring and summer

(Figure 2.13). Harbor seals decreased food intake with increasing

photoperiod throughout the entire range of daylengths (Figure

2.14). No clear trend between photoperiod and food intake was

observed for the two ringed seals (Figure 2.15). Harp seals in

the wild experience a different pattern of change of daylength

throughout the year, because of their annual migration. However,

the photoperiods experienced by the seals studied, and those

experienced by wild seals were not different during the periods of









the year in which photoperiod had an effect on food intake (spring

and summer) (Figure 2.16).

No previous study has addressed the possible changes in the

level of energy expenditure throughout the year in northern seals.

My study demonstrated that almost 40% of the variability in energy

expenditure was related to seasonal effects. Given that a major

component of the energy expenditure of homeotherms is the basal

rate of metabolism, these results point to the possibility that

basal metabolism changes throughout the year in these species.










Proximate composition of herring, Clupea harengus,


fed to seals kept at the Ocean Sciences Centre, Logy Bay,


Newfoundland


(fresh weight basis).


Fed-from Fed-to N Protein, % Lipid, %
x SE R SE


20-Apr-91
09-Aug-91
19-Nov-91
01-Apr-92
02-May-92
09-May-92
22-May-92
05-Aug-92
01-Jan-93
02-Nov-93
06-Nov-93
04-Jun-94
09-Dec-94
14-May-95
16-Oct-95
02-Oct-96


08-Aug-91
18-Nov-91
31-Mar-92
01-May-92
08-May-92
21-May-92
04-Aug-92
10-Aug-92
01-Nov-93
05-Nov-93
04-Jun-94
16-Jun-94
13-May-95
25-Aug-95
09-May-96
31-Oct-96


17. 3
18.8
16.7
17.4
17.4
17.3
15.5
16.1
21.0
19.5
19.5
19.8
17. 1
18.7
18.7
18.1


0.84
0.93
0.80
0.84
0.84
0.83
0.73
0.77
0.47
0.29
0.25

0.50
0.60
0.56
0.67
0.31


11.3
7.6
13.9
9.9
6.3

6.4
15.4
9.3
10.0
16.1
16.7
11.2
12.3
8.7
11.8
6.2


0. 50
0.31
0.64
0.43
0.25

0.26
0.72
0.40
0.76
1.60
0.48
3.18
0.37
0.98
1.29
0.23


Energy, kJ/g
R SE

8.4 0.39
7.3 0.06
9.2 0.59
7.8 0.47
6.5 1.03
6.4 0.72
9.6 0.71
7.3 0.32
9.8 0.23
10.7 0.56
11.0 0.15
8.9 1.13
8.7 0.28
7.7 0.33
8.9 0.59
6.6 0.02


01-Nov-96 20-Aua-97 10 19.1 0.47 8.4 0.67 7.7 0.28


7.7 0.28


01-Nv-96 20-A a-9


Table 2. 1.


10 19.1 0.47 8.4 0.67










Table 2.2. Periods (seasons) among which years were divided in
relation to daylength observed in Logy Bay, Newfoundland
(4738'N, 5240'W).

Minimum Maximum
Period day day Change in
Start End length length length daylength
(days) (h) (h) (min/d)
Decreasing
days(Fall) Aug 6 Nov 4 91 9.9 14.7 3.3
Short days
(Winter) Nov 5 Feb 6 94 8.4 9.8 1.8
Increasing
days (Spring) Feb 7 May 6 89 9.9 14.7 3.4
Long days
(Summer) May 7 Aug 5 91 14.8 16.0 1.6










Table 2.3. Seasonal changes in body mass, energy intake, and
requirements of captive phocid seals. Means from each seal used
in these calculations were previously weighted by the number of
observations taken from each individual.

Fall Winter Spring Summer
Pagophilus groenlandicus
Number of seals studied 7 7 7 8
Seasons per seal 3.2 3.2 3.4 3.7
Body mass, kg Mean 133.6 159.2 163.8 131.7
SE 29.44 31.05 21.91 22.17
Daily mass change, g/d Mean 53.5 440.9 -326.5 -39.2
SE 104.31 71.84 281.11 142.16
Maintenance energy, MJ/d Mean 24.3 34.7 38.7 27.1
SE 1.41 2.49 4.96 1.84
Digestible energy, MJ/d Mean 27.0 44.2 31.1 27.4
SE 2.61 2.72 2.70 4.09
Growth efficiency, g/MJ Mean 38.4 62.8 60.0 28.5
SE 5.64 35.91 14.31 8.06
Phoca vitulina
Number of seals studied 6 6 6 6
Seasons per seal 4.9 5.0 4.6 5.7
Body mass, kg Mean 80.6 89.6 89.8 90.3
SE 3.03 6.36 4.22 5.79
Daily mass change, g/d Mean 132.6 48.5 44.3 -203.3
SE 181.12 57.67 31.84 137.67
Maintenance energy, MJ/d Mean 29.3 22.2 19.1 22.5
SE 5.07 6.63 5.96 4.40
Digestible energy, MJ/d Mean 31.3 25.2 22.9 21.4
SE 2.67 4.31 4.31 2.87
Growth efficiency, g/MJ Mean 94.5 4.3 205.2 13.1
SE 138.00 49.96 490.82 42.83
Phoca hispida
Number of seals studied 2 2 2 2
Seasons per seal 2.0 2.0 2.0 2.5
Body mass, kg Mean 44.8 46.7 46.5 42.8
SE 4.25 5.28 0.92 1.01
Daily mass change, g/d Mean 16.4 0.6 29.8 -34.6
SE 20.64 14.61 10.89 89.18
Maintenance energy, MJ/d Mean 11.8 13.5 13.8 11.7
SE 0.24
Digestible energy, MJ/d Mean 13.1 12.6 15.2 11.1
SE 1.05 0.09 0.46 3.02
Growth efficiency, g/MJ Mean 39.8 39.8 49.3 59.2
SE 5.79










Table 2.4. Yule-Walker probability values for the
autocorrelation-corrected regression of daily energy intake
(MJ/day) against date, daylength, temperature (C), and average
solar radiation (MJ/m2) for 16 northern phocid seals held captive
at the Ocean Science Centre, Logy Bay, Newfoundland (47'38'N,
52'40'W).

Solar
Seal Date Daylength Temperature Radiation
Pagophilus
groenlandicus BAB 0.0001 0.0001 0.0383 0.4354
CHE 0.5836 0.9940 0.0789 0.9044
ELM 0.0084 0.0002 0.5416 0.5857
MIC 0.0001 0.0001 0.1954 0.0154
RHO 0.0017 0.0001 0.0735 0.6748
TYL 0.1280 0.0040 0.9822 0.6708
Vic 0.6501 0.0134 0.8019 0.2063
VIR 0.0002 0.0001 0.1746 0.3579
Phoca vitulina CAE 0.0112 0.0051 0.0063 0.0728
CLA 0.0087 0.0064 0.3327 0.4478
DAR 0.2370 0.7146 0.2424 0.2767
JUL 0.1130 0.0076 0.0046 0.3369
KEV 0.3148 0.0230 0.3047 0.4187
OSC 0.6162 0.0076 0.0778 0.6011

P. hispida LER 0.1424 0.1524 0.6586 0.4824
MEG 0.0205 0.0090 0.5848 0.3169













300
280-
260-
__240,
C" 220-
~ 200,
n 180 ,
CU160-
~140
120
100
80
88 89 90 91 92 93 94 95 96 97

Year
Figure 2.1. Body mass record of female harp seal (Pagophilus
groenlandicus) BAB kept outdoors in Logy Bay, Newfoundland
(47-38'N, 5240'W).












CD)

CU
5


Cf
C,)
2t


130
120-
110-
100-
90-


80


60
50

200

180

160

140

120

100

80


p


88 89 90 91 92 93 94 95 96 97


88 89 90 91 92 93 94 95 96 97

Year
Figure 2.2. Body mass records of harp seals (Pagophilus groenlandicus)
kept outdoors in Logy Bay, Newfoundland (47'38'N, 52'40'W). a) female
CHE; b) male ELM.







80~

701LA


CY 60-

cn50-
C,,
(U
05;40-


88 89 90 91 92 93 94 95 96 97


c')

C,)
C,)
(


30-
20

160
140
120
100
80
60


40
20


88 89 90 91 92 93 94 95 96 97


Year
Figure 2.3. Body mass records of harp seals (Pagophilus groenlandicus)
kept outdoors in Logy Bay, Newfoundland (47'38'N, 52'40'W). a) male
JAM; b) male MIC.


I U












Cn)
C,)
CU


C)
C,)
CU


160

140

120-

100-

80-

60

40


Y


88 89 90 91 92 93 94 95 96 97
220
200 -
180
160 '

140-
120
100


80
60


88 89 90 91 92 93 94 95 96 97

Year
Figure 2.4. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay, Newfoundland (47038'N,
52'40'W). a) female RHO; b) male TYL.


m
5











CD,
C',
CU


C,)
C,,
CU


250

200

150

100

50-

0


U


8889909 1 1923999697


88 89 90 91 92 93 94 95 96 97
180-

160-

140-

1201


100-

80


88 89 90 91 92 93 94 95 96 97

Year
Figure 2.5. Body mass records of harp seals (Pagophilus
groenlandicus) kept outdoors in Logy Bay, Newfoundland (47'38'N,
52'40'W). a) male VIC; b) male VIR.


h







110
1001


CD)
Cn
CU


C,)
CU


90.
80'
70'
60-
50'
40-
30-
20

120

110'

100'

90'

80-

70-

60


88 89 90 91 92 93 94 95 96 97


88 89 90 91 92 93 94 95 96 97
Year
Figure 2.6. Body mass records of harbor seals (Phoca vitulina)
kept outdoors in Logy Bay, Newfoundland (47038'N, 52'40'W). a)
male CAE; b) male CLA.


I I I I I I I I I I







100


C)
Cu,
5U


90-
80
70
60
50-
40-
30-
20
10


I I I v


88 89 90 91 92 93 94 95 96 97
120
110 ,


CD
IV
C,)
(U
Cu
5O


100-
90-
80
70-
601


50.
40.
30


88 89 90 91 92 93 94 95 96 97


Year
Figure 2.7. Body mass records of harbor seals (Phoca vitulina) kept
outdoors in Logy Bay, Newfoundland (47'38'N, 52'40'W). a) male DAR; b)
male JUL.







120


CD

CU


110
100
90-
80
70-
60-
50-


40
30


1 9 1


88 89 90 91 92 93 94 95 96 97
130
1201


(U
:'I


110-
100-
90
80


70
60


S S S S S S


88 89 90 91 92 93 94 95 96 97

Year
Figure 2.8. Body mass records of harbor seals (Phoca vitulina) kept
outdoors in Logy Bay, Newfoundland (4738'N, 52140'W). a) female KEV;
b) male OSC.


t &w







6
50


0,)
C,)
CU


40

30*

20-


10

0


11!


88 89 90 91 92 93 94 95 96 97
55
50


C,)
CU


45-
40
35-


30


25-


20
15


U U U S


88 89 90 91 92 93 94 95 96 97
Year
Figure 2.9. Body mass records of ringed seals (Phoca hispida) kept
outdoors in Logy Bay, Newfoundland (47038'N, 52040'W). a) male LER; b)
female MEG.


I


I I I I


1 9












111
1.01-
c 0.9
to) II
m 0.8
E
1Pv
0
.o 10
-0 1.0
a) 0.9
>
M 0.8

1.1
1.0
0.9
0.8
Fall Winter Spring Sumnmer




Figure 2.10. Seasonal changes in relative body mass (mass
observed / mass predicted by the regression of mass against date)
in seven adult harp seals (Pagophilus groenlandicus, Pg); six
harbor seals (Phoca vitulina, Pv); and two ringed seals (Phoca
hispida, Ph). Animals were fed ad libitum and held outdoors at
the Ocean Sciences Centre, Logy Bay, Newfoundland (47038'N,
52040'W).










1.4
m 1.2
40-a
1.0

L 0.8
c 1.4
a) Pv
a) 1.2
4 1.0
C,)
a)
0.8
S1.4-
a) Ph
1.2-
a) 1.0o
0.8-
Fall Winter Spring Summer





Figure 2.11. Seasonal changes in relative digestible energy
intake, DEI (DEI observed / DEI predicted by the regression of DEI
against date) in seven adult harp seals (Pagophilus groenlandicus,
Pg); six harbor seals (Phoca vitulina, Pv); and two ringed seals
(Phoca hispida, Ph). Animals were fed ad libitum and held
outdoors at the Ocean Sciences Centre, Logy Bay, Newfoundland
(47-38'N, 5240'W).












L_


0

(E
E


1.2

1.0

0.8

1.2

1.0

0.8

1.2

1.0

0.8


I


Fall Winter Spring Summer





Figure 2.12. Seasonal changes in relative maintenance energy
requirements, MER (MER observed / MER predicted by the regression of
MER against date) in seven adult harp seals (Pagophilus
groenlandicus, Pg); six harbor seals (Phoca vitulina, Pv); and
two ringed seals (Phoca hispida, Ph). Animals were fed ad
libitum and held outdoors at the Ocean Sciences Centre, Logy Bay,
Newfoundland (4738'N, 52'40'W).


-Pv










70


V



n


q


60-

50
40-

30-

20-


10 1 1I
0I I I
8 9 10 11 12 13 14 15 16

Daylength





Figure 2.13. Relationship between photoperiod and food intake of
adult harp seals (Pagophilus groenlandicus) kept outdoors at the
Ocean Sciences Centre, Logy Bay, Newfoundland (47'38'N, 52'40'W).










45


V


40


35


30-

25

20


15


I a I I I I I I


8 9 10 11 12 13 14 15 16

Daylength





Figure 2.14. Relationship between photoperiod and food intake of
adult harbor seals (Phoca vitulina) kept outdoors at the Ocean
Sciences Centre, Logy Bay, Newfoundland (4738'N, 52'40'W).










25


0


20-

15-

10-

5-


8 9 10 11 12 13 14


15 16


Daylength





Figure 2.15. Relationship between photoperiod and food intake of
adult ringed seals (Phoca hispida) kept outdoors at the Ocean
Sciences Centre, Logy Bay, Newfoundland (4738'N, 52'40'W).


I.
I























J F M


A M J J A


S O N D


Month



Figure 2.16. Photoperiods experienced by captive harp seals
(Pagophilus groenlandicus) kept at the Ocean Sciences Centre
(OSC), Logy Bay, Newfoundland (4738'N, 52040'W), and that
hypothesized for harp seals in the wild during their annual
migration.


In the wild
U


26
24
22
20
18
16
14
12
10
8
6


4-'
c,)
a)
(U
0
















CHAPTER 3
BASAL RATES OF METABOLISM OF PHOCID SEALS


Introduction

Pinnipeds are an especially difficult group within which

study basal rates of metabolism. Their body sizes range from

large to enormous (25 to 4,000 kg); live in both aquatic and the

terrestrial environments; and are likely to undergo profound

metabolic changes throughout the annual cycle, from intense

feeding to fasting while reproducing and moulting. Major problems

with the existing data on pinniped metabolic rates include the use

of immature animals, the measurement of metabolic rates in

restrained animals, and the lack of control for activity, post

absorptive status, and period of inactivity (Schmitz and Lavigne

1984, Lavigne et al. 1986).

Growing mammals clearly exhibit increased metabolic rates in

relation to their body size (Brody 1945). Restrained animals, on

the other hand, can be under severe stress, exhibiting high

metabolic rates. Conversely, it has been observed that metabolic

rates are depressed during diving activity (Kooyman et al. 1980).

In addition, oxygen consumption decreases during sleep. As an

example, fasting grey seal pups can lower their metabolic rate as

much as 48 % when sleeping (Worthy 1987). Also, in the California

sea lion, metabolic rate while sleeping can be 24 % less than when









awake (Matsuura and Whittow 1973). It is clear that measurements

of metabolic rates under standard conditions are needed to build

meaningful energy budgets for pinnipeds.

My objectives were to determine basal rates of metabolism on

three species of phocid seals. Concurrently, I also intended to

establish the changes in metabolic rate due to age, to determine

the possible differences in metabolic rates between seals in water

and resting on a dry substrate, and to explore whether moulting

had an effect on metabolic rates.


Material and Methods

I measured metabolic rates of nine harp, three harbor, and

one ringed seal by determining their rate of oxygen consumption

through open-flow respirometry. Oxygen consumption was measured

from post-absorptive (> 16 h post-prandial) animals at different

ambient temperatures for periods of two to four hours.

To measure oxygen consumption in air, I built a metabolic

chamber to control ambient temperature during determinations. The

chamber was 2.4 x 1.0 x 0.9 m internally, with an empty volume of

2.16 m It had two doors and a temperature-control system

consisting of a water bath of 11,000 BTU capacity that controlled

the temperature of a glycol solution pumped through a series of

radiators inside the metabolic chamber to maintain a constant

internal temperature (Figure 3.1). The measurement of oxygen

consumption throughout a range of ambient temperatures gave

certainty that metabolic measurements were made within the range









of thermal neutrality, a basic condition for obtaining valid

estimates of basal metabolism.

For some animals, I measured oxygen consumption while the

seal was in water, as well as when it was in air. For the former,

I used a 1.8-m diameter tank filled with water just enough depth

to keep the seal submersed to minimize the space available for

swimming. This tank was airtight; it was also designed for

measurements of oxygen consumption by other researchers (Renouf

and Gales 1994). The tank was filled with non-circulating

seawater pumped from the nearby Logy Bay. Water temperatures

during measurements ranged between 0 and 30C.

Fresh air was pumped to both chambers at a rate that varied

between 100 and 150 1/min, depending on the size of the animal.

The flow rate was measured using a Cole-Parmer gravimetric

flowmeter (Vernon Hills, Illinois). Given the large volumes of

air introduced in the chamber, no attempt was made to remove water

before measuring the airflow. Consequently, the humidity of the

incoming air was constantly measured using a Cole-Parmer

thermohygrometer (Vernon Hills, Illinois) to subtract the volume

of water vapor from the volume of air introduced in the chamber.

A small sample of air was constantly drawn from the chamber

at a rate of 150 ml/min. This air sample was first passed through

soda lime and silica gel to remove carbon dioxide and water,

respectively. The content of oxygen in the sample of air was then

determined using a SA-3 AMETEK oxygen analyzer (Pittsburgh,

Pennsylvania). The temperature of the chambers, and that of the









air at the point of measurement of flowrate, was determined with

copper-constatant thermocouples.

The calculation of the rate of oxygen consumption was made

using the oxygen concentration that was maintained constant for at

least 10 min during the two- to four-hour measurement period.

Animals were first acclimatized to the chamber for periods of 2-4

hours during two weeks before commencing measurements.

I tested possible differences in resting metabolic rates

between measurements done in water and in air and between

measurements performed during the moult or before its onset using

paired t-tests of data collected from the same animals during the

same season. I tested for the effect of body mass and age on

resting metabolic rates using correlation analysis. I also tested

the hypothesis that basal rates of metabolism of northern seals

are not different from those of terrestrial mammals by comparing

them to those calculated using predictive equations available from

the literature (Kleiber 1961).


Results

Rates of oxygen consumption of seals measured while resting

varied between 14.2 and 39.6 1/min, whereas mass-specific rates

ranged between 0.17 and 0.38 ml/g h (Table 3.1). The comparison

of rates of oxygen consumption taken while the animal was in water

and in air revealed no differences (paired t-test = -0.25, d.f. =

8, P = 0.807). However, the ring seal did increase its metabolic









rate while in water by 54%, probably because its small size

allowed it to swim despite the small amount of water in the tank.

The moult did not have an effect on metabolic rates. The

comparison of measurements of rates of oxygen consumption of seals

during the moult period and before its onset revealed no

significant differences (paired t-test = 1.4, d.f. = 7, P = 0.22).

Metabolic rates of adult harp seals did not change with

ambient temperature in the range of -12 to 15'C. Above this

temperature, there was an increase in the rate of oxygen

consumption (Figure 3.2). Consequently, only values obtained

below 150C ambient temperature were used to estimate basal rates

of metabolism.

I found that the adult seals had basal rates of metabolism

higher than predicted by Kleiber's (1961) equation (paired t-test

= 4.1, d.f. = 9, P < 0.003). Harp seals had a basal rates of

metabolism 29 % higher than expected (paired t-test = 2.2, d.f. =

5, P < 0.04), whereas the basal rate of metabolism of harbor seals

was 69 % higher than expected for mammals of similar size (paired

t-test = 5.5, d.f. = 2, P < 0.02). The only ring seal studied had

a basal rate of metabolism 45 % higher than expected for its mass.

Regression analyses demonstrated a significant logarithmic

relationship between resting rates of metabolism and mass of the

seals studied (r2 = 0.72, d.f. = 11, P < 0.0003). Basal metabolic

rates of adult seals were also related to body mass (r2 = 0.48,









V02
d.f. = 8, P < 0.026), and best described by the formula: (ml/g

h) = 2.21-Mb(g -0.55 (Figure 3.3).

Body temperature did not change with ambient temperature in

two of the three adult male harp seals studied (r2 = 0.004, d.f. =

27, P = 0.74), but increased with decreasing ambient temperatures

in the male harp seal ELM (r2 = 0.53, d.f. =12, P = 0.006) (Figure

3.4).


Discussion

Metabolic rates measured while the animal was in water were

not different from those measured while in air. However, when the

animal was allowed to swim, metabolic rates were higher in water.

Aside from the complications inherent to the difficulty of

controlling activity in water, it has been found that metabolic

rates are inversely correlated to the proportion of time spent

underwater (harp seals, Gallivan 1981; Weddell seals, Castellini

et al. 1992). Despite the fact that I did not find differences

between measurements made in water or air, it is still preferable,

for the sake of comparability, to use measurements of oxygen

consumption in air to estimate basal rates of metabolism of

pinnipeds.

There were no differences between metabolic rates before or

during the moult in harp seals. There are conflicting reports

regarding the influence of moult on phocid energetics. On one

hand, some studies have documented a decrease in basal metabolic

rates during the moult in yearling harbor seals (Ashwell-Erickson









and Elsner 1981). These authors suggested that the decrease might

be due to the observed decrease in plasma thyroxine that has been

reported during moult. However, other studies have produced

conflicting results in relation to changes in the levels of

thyroxine during moult. Harbor seals kept at the Ocean Sciences

Centre showed no clear pattern of thyroxine levels in relation to

the moult. Indeed, two animals had the highest thyroxine plasma

level of a complete year cycle during the moulting period (Renouf

and Brotea 1991). On the other hand, grey seals showed that

juveniles had higher resting metabolic rates during the moult, but

adults did not (Boily and Lavigne 1997). During the moult, phocid

seals tend to spend more time hauled out and thus they probably

have lower levels of activity and food intake. The increased time

hauled out has been hypothesized to be due to the requirement for

a higher skin temperature to promote rapid skin and hair

regeneration (Ling 1974).

The thermoneutral zone, the range of ambient temperature in

which the rate of metabolism is minimal and independent of

temperature, ranged between 15C and, at least, -120C. Irving and

Hart (1957) found that young harbor seals did not increase

metabolic rates between -10 and 300C while in air. The same

animals increased metabolic rate when in water below 100C. In

contrast, Hansen et al. (1995) found that juvenile harbor seals

increased their rate of metabolism below -2.3C and above 250C air

temperature. Rates of metabolism for an adult harbor seal have

been reported to stay constant from 20 to 35C ambient









temperature, although an increase in rectal temperature was

observed above 300C ambient temperature (Matsuura and Whittow

1973). The larger size and more arctic distribution of harp seals

may explain why they have a larger ability to withstand low

ambient temperatures than harbor seals and start to increase

metabolic rates when ambient temperature rises above only 150C.

Unlike harbor seals, harp seals always haul out on pack ice where

ambient temperatures are low and windshield effects are likely to

be important.

I found that basal rates of metabolism of the three species

of phocid seal studied were higher than values predicted by

Kleiber's (1961) equation. Another recent study of basal

metabolism of grey seals found basal rates 10 to 50 % higher than

those predicted by mass using Kleiber's (1961) relationship (Boily

and Lavigne 1997). Higher metabolic rates of pinnipeds may not be

related to aquatic habits, as was originally proposed (Schmidt-

Nielsen 1983), but to their food habits. Terrestrial strict

carnivore groups, such as felids, also have basal metabolic rates

that are higher than predicted by mass (McNab, pers. comm.). The

long-standing controversy regarding whether pinnipeds (and marine

mammals in general) have higher basal rates of metabolism may have

arisen from the lack of control of the variables that influence

basal rates. Measurements taken at different times of the year

can provide different estimates of basal rates (Boily and Lavigne

1997, chapter 4, this study). Also, the use of forced restraint,

the lack of control of activity, and the allowance of diving might






52


contribute to the variation in reported values. Furthermore, the

fact that basal rates of metabolism of a species do not differ

from those predicted using Kleiber's (1961) equation does not mean

that they are not different from those of terrestrial mammals.

Kleiber based his equation on a limited set of species, mostly

domesticated, and thus, it cannot be assumed that it will

represent the "average" terrestrial mammal (McNab 1997).











Table 3.1. Total (V02) and mass-specific (V02/Mb) resting
metabolic rates of individual harp Pagophilus groenlandicus,
harbor Phoca vitulina, and ringed P. hispida seals.

Seal N Age Body V02 VO2/Mb

(months) mass (kg) (l/h) (ml/g h)

Pagophilus groenlandicus
BAB 11 > 144 Mean 219.6 39.5 0.18
SE 16.52 0.18 0.017
BRU 7 1 Mean 31.8 10.9 0.34
SE 3.78 0.34 0.068
ELM 43 > 144 Mean 132.1 32.3 0.24
SE 2.26 0.24 0.008
JAM 5 37 Mean 71.0 20.1 0.28
SE 0.67 0.28 0.041
MIC 7 > 84 Mean 102.8 32.0 0.31
SE 0.60 0.31 0.008
RHO 6 > 84 Mean 100.7 34.4 0.34
SE 3.27 0.34 0.011
TYL 64 81 Mean 163.0 27.3 0.17
SE 2.91 0.17 0.006
VIC 5 45 Mean 173.2 39.6 0.23
SE 12.30 0.23 0.008
VIR 53 > 144 Mean 128.2 26.5 0.21
SE 1.99 0.21 0.006
Phoca vitulina
CAE 5 129 Mean 81.6 31.2 0.38
SE 0.35 0.38 0.052

CLA 9 225 Mean 85.8 24.5 0.29
SE 1.33 0.29 0.023

JUL 5 141 Mean 89.0 29.7 0.33
SE 2.73 0.33 0.036
Phoca hispida
LER 8 81 Mean 44.6 14.2 0.32
SE 3.57 0.32 0.037
















AMETEKN
Oxygen
Analyzer


Figure 3.1. Metabolic chamber used in measuring oxygen
consumption of phocid seals in air. A temperature-controlled
water bath controlled the temperature of a glycol solution
circulated through a series of four radiators placed in a special
funnel inside the chamber. Air was forced through these
radiators to control the chamber temperature.











0.5


-"

E

0
U>


0.4-

0.3-

0.2-


0.1

0.0


-10


10


20


30


Ambient temperature (0C)



Figure 3.2. Relationship between resting oxygen consumption rate
and ambient (air) temperature for three adult male harp seals
(Pagophilus groenlandicus).


0@


0.0


0
0


-S V0
* .0
S.







Pagophilus groenlandicus
v Phoca vitulina
0 Phoca hispida


100


Body


150


200


mass (kg)


Figure 3.3. Oxygen consumption rates under basal conditions of
six harp seals (Pagophilus groenlandicus), three harbor seals
(Phoca vitulina), and one ring seal (P. hispida) in relation to
their body mass.


0.5


E

0
.>


0.4-

0.3-


0.2


0.1


50


250















U
0
(.0
k


36.4-
36.2-
36.0-
35.8-
35.6-
35.4-


35.2
35.0


-10 -5 0 5 10 15 20 25 30


Ta


(0c)


Figure 3.4. Body temperature of three adult male harp seals
(Pagophilus groenlandicus) in relation to ambient (air)
temperature.


A A
AA



AA ELM
0 VIR
0 TYL


9 1 9 1 1 m1(
















CHAPTER 4
SEASONAL CHANGES IN BASAL RATES OF METABOLISM OF HARP SEALS


Introduction

A large proportion of the energy expenditure of endotherms

is devoted to basal metabolism. Thus, animals might be expected

to decrease these rates during periods when food is scarce or of

poor quality. Basal rates of metabolism have been hypothesized to

be merely the cost of maintaining the necessary metabolic

machinery capable of producing maximum sustained metabolic rates,

the ultimate target of natural selection (Kersten and Piersma

1987). A major contributor to basal rates of metabolism is

respiration of organs involved in nutrient and energy processing,

such as the alimentary tract, liver, and kidneys. In ruminants,

it has been established that liver and gut are responsible for

about 50 % of the basal metabolic expenditure (Johnson et al.

1990). A study comparing different strands of laboratory mice

determined that basal metabolic rates were strongly correlated to

the mass of internal organs (Konarzewski and Diamond 1995). In

reproducing lab mice, principal component analysis demonstrated

that the combined alimentary effects explained 72% of the

variation in basal rates of metabolism (Speakman and McQueenie

1996).









The observed correlation between organ sizes and basal rates

of metabolism may be interpreted as evidence for the ability to

change basal rates in relation to the amount of nutrient and

energy that needs to be processed. In this respect, basal rates

were found to correlate with energy assimilation rates (Falco

tinnunculus: Daan et al. 1989; lab mice: Konarzewski and Diamond

1994).

Given the profound variation in food intake and energy

expenditure observed in pinnipeds in general, and phocid seals in

particular (chapter 2) basal rates of metabolism may be

hypothesized to vary throughout the annual cycle. Given that

energy intake of harp seals, in relation to body mass, was shown

minimal during summer and maximal during winter, I hypothesize

that a similar trend will be observed for basal rates of

metabolism. A previous study conducted at the Ocean Sciences

Centre, however, concluded that harp seals had higher basal rates

of metabolism during spring and summer as compared to the rest of

the year (Renouf and Gales 1994).


Material and Methods

I measured metabolic rates of three adult male harp seals by

determining their rate of oxygen consumption through open-flow

respirometry. Oxygen consumption was measured from post-

absorptive animals at different ambient temperatures for periods

of 2-4 hours. Determinations of oxygen consumption rates were

made in October, January, April, and July (10-18 per month). This

design allowed me to compare basal rates of metabolism between









seasons with enough replicate measurements per seal to provide

robust comparisons. I measured oxygen consumption following the

methodology described in chapter 3. I tested the influence of

seasonality using general linear models that included "seal" as a

factor and body mass as a covariate.


Results

In total, I obtained more than 200 measurements of oxygen

consumption rates throughout the entire study period. Metabolic

rates of the three males studied were determined throughout a wide

range of ambient temperatures (Figure 3.2). To estimate basal

rates of metabolism, I chose to use only the measurements obtained

below 15'C, given that seals increased their metabolic rate above

this temperature (t=2.1, d.f. = 57, P<0.04). In this analysis, I

used only 89 determinations of oxygen consumption that met the

conditions for basal rates of metabolism.

Changes in basal metabolism and body mass throughout the

annual cycle can be observed in Figures 4.1 4.3. I found that

season had an effect on basal rates of metabolism. In the general

model that included "seal" as a factor, season explained 32.9 % of

the total variation in basal rates of metabolism (F3,88 = 25.94, P

< 0.0001) and individual differences accounted for 33.5 % of that

variation (F2,88 = 26.39, P < 0.0001). Body mass did not have an

effect on basal rates of these three seals (F1,88 = 0.26, P <

0.612). Multiple comparisons revealed that the effect of season

was due to summer values being lower than values from all other

seasons. The analysis of data on a seal by seal basis showed the









same trend (Table 4.1). As in the overall test, basal rates

during summer were lower than during the rest of the year for the

three males studied (Table 4.2, Figures 4.1 4.3). The decline

in basal metabolism during summer was remarkably similar among the

three males studied. Summer basal rates were 60.4%, 59.3%, and

61.3% of the mean value for the rest of the year for the three

adult males studied.

Mass-specific basal rates of metabolism were also influenced

by seasonality. I found that 36.9% of the total variation in

mass-specific rates was accounted by seasonal effects, while 32.8%

was accounted by individual differences (F3,88 = 33.63, P < 0.0001;

2,8 = 29.89, P < 0.0001, respectively). Although body mass

explained only 6.0% of the total variation in mass-specific basal

rates of metabolism, it did have an effect (Fi,88 = 5.43, P <

0.0222). Multiple comparisons demonstrated that only winter and

summer values were not different. The analysis of the data from

the individual seals produced similar results for the significance

of the seasonal effects (Table 4.1), and the multiple seasonal

comparisons (Table 4.2).


Discussion

My results support the hypothesis that basal rates of

metabolism of phocid seals change throughout the annual cycle, and

that this variation is probably related to the observed seasonal

changes in food intake.









The confirmation of the expected trend of lower levels of

basal metabolism during summer is at odds with previous research

conducted by the late Dr. Renouf and collaborators on harp seals

housed at the Ocean Sciences Centre. These researchers found

that, contrary to predictions based on thermoregulatory and

reproductive considerations, harp seals had higher basal rates of

metabolism in summer than during the rest of the year. My results

clearly contradict the previous report by Renouf and Gales (1994).

At least two factors may explain this disagreement. First, the

previous study measured oxygen consumption throughout a 24-hour

cycle of seals kept in a tank fitted with a Plexiglas bubble from

which air samples were drawn. Seals were free to swim inside the

tank during that time. To control for the effect of physical

activity on oxygen consumption, these authors chose the hour with

the lowest oxygen consumption as a measure of basal rates. As

such, the methodology was probably sensitive to seasonal changes

in activity. The minimal activity in a 24-hour period of a male

seal near the breeding season (especially if sexually mature

females are nearby) might be higher than that of a resting seal.

Another, perhaps more important drawback of the previous study is

that the design was not balanced. Single 24-hour measurements

were made at various intervals, from two weeks to two months. So,

for some animals there were only two measurements representing an

entire season.

In my design, I explicitly avoided the complications of

allowing animals free movement during the determination of oxygen










consumption rate. As mentioned in the methods section of chapter

3, I used a "dry" metabolic chamber in which the animal laid down

during measurements. In addition, I measured oxygen consumption

rates of every seal more than 10 times each season, and kept the

period between seasonal measurements constant (60 days).

I believe my results accurately reflect the changes in basal

rates of metabolism experienced by harp seals in captivity, and in

the wild. My results agree with what would be expected of mammals

exposed to varying levels of food intake and energy balance.

During spring and summer, although energy expenditure is

relatively high, food consumption is not, resulting in a negative

energy balance (body mass loss). As expected, basal rates are

lower during this phase of the annual cycle, and probably

represent an adaptation to slow the rate of body mass loss during

this period. In addition, as food consumption is low, visceral

organs probably recess in size and/or metabolic activity, as

compared with periods of intense feeding during the fall.

A recent study has shown that captive grey seals have a

similar pattern of seasonal changes in basal rates of metabolism.

In that study, basal rates during the summer were found to be up

to 50% lower than in the other seasons for the three females

studied (Boily and Lavigne 1997). Unfortunately, these authors

did not provide information on food intake levels or patterns of

body mass change of these animals, although they stated the seals

were fed and ate daily.






64


Table 4.1. Results of the analysis of variance, ANOVA (F
statistic, F and probability value, P) used to test the influence

of season on total (V02) and mass-specific (VO2/Mb) basal
metabolic rates of three adult male harp seals, Pagophilus
groenlandicus.

Seal V02 V 2 0 VO2 /Mb V02 /Mb


F P F P
ELM 16.14 0.0001 11.91 0.0001
TYL 14.61 0.0001 21.98 0.0001

VIR 8.36 0.0002 6.89 0.0006






65




Table 4.2. Comparison of total (V02) and mass-specific

(V02/Mb) basal metabolic rates among seasons for three adult
harp seals, Pagophilus groenlandicus. Cells containing the "less
than" sign (<) indicate that the first season represented in the
column header had significantly lower values than the second
season.

Variable Seal Su1-W2 Su-F3 Su-Sp4 W-F Sp-F W-Sp

ELM < < <
02 TYL < < < <
V02

VIR < < <


ELM < < <
02 /Mb TYL < < < < <
S02 /Mb

VIR< < <<


1 u 2 = 3 =
summer, =winter =fall,


= spring







800


E


0


CD)
C,,
CU


600-


400-


200-


0
225

200-

175-

150-

125-

100-


Oct


S
U.


Jan


Apr


Jul


Figure 4.1. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the adult male harp
seal, Pagophilus groenlandicus, ELM.


T
tr







800


-

E
N
0
a>


Cn


'V


600


400-


200


0
225

200

175

150

125

100.


Oct


Jan


Apr


Jul


Figure 4.2. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the adult male harp
seal, Pagophilus groenlandicus, TYL.


0


.__I





0







800


E
-J
E
N
U>


600-


400-


200


0
225

200


U)
C,)
(U


175

150-

125-

100.


Oct


Jan


Apr


Jul


Figure 4.3. Seasonal variation in basal rates of oxygen
consumption (top) and body mass (bottom) of the adult male harp
seal, Pagophilus groenlandicus, VIR.


HI


0











0.35
0.30
Y 0.25
_1 0.20 -./1

E 0.15 "
\ 0.10
0 -- ELM
> 0.05 TYL
-~'- VIR _ _ _
0.00 -I

Oct Jan Apr Jul





Figure 4.4. Seasonal variation in mass-specific basal rates of
oxygen consumption for three adult male harp seals (Pagophilus
groenlandicus) .
















CHAPTER 5
INFLUENCE OF BODY COMPOSITION ON SEASONAL CHANGES OF ENERGY
EXPENDITURE OF CAPTIVE HARP SEALS


Introduction

Knowledge of body composition is essential for studies of

energy allocation. As is well known, the energy equivalencies of

the different components of the body are quite different, from 0

for water to 38.9 kJ/g for fat. Although most of the energy

mobilized involves fat depots, a large proportion might involve

changes in the lean portion of the body. In fasting northern

elephant seal pups the proportion of body fat did not change

during the 2-3 month postweaning fast (Adams and Costa 1993).

Although the different body components were used in the same

proportion, protein catabolism accounted for only 4% of the energy

(Pernia et al. 1980, Rea and Costa 1992).

Changes in the body composition of animals may also affect

rates of metabolism. Metabolic rates of human subjects correlate

better with lean body mass than with total body mass (Felig et al.

1983, Segal et al. 1989), suggesting that fat tissue does not

contribute to the total metabolism. However, other studies

involving rats (Rattus norvegicus) and sheep have found that fat

does contributes to the overall metabolism (McCracken and McNiven

1983, McNiven 1984).









The objectives of this part of the study were to determine

the body composition of adult harp seals, and how it changes

during the year. These results were used to determine the

relationship between seasonal changes in body mass and changes in

the energy content of the body, and between changes in body

composition and the seasonal variation in metabolic rates.


Material and Methods

I determined the body composition of the four adult harp

seals (BAB, ELM, TYL, and VIR) during each season. I used the

method of isotope dilution (reviewed by Speakman 1997) that

provides accurate estimates of the water content of the body. In

early November, February, May, and July, each animal was

physically restrained, after intramuscular administration of

Valium (5 mg/ml, Roche Laboratories) at an approximate dose of 1.5

mL/100 kg, to facilitate handling. A known amount of deuterium

oxide (D20, 99.9% purity, Cambridge Isotope Laboratories, Andover,

MA) was administered using a stomach tube, at an approximate dose

of 0.5 g/kg. The complete delivery of the isotope was secured by

flushing the syringe and stomach tube with small amounts of water

and air.

Blood samples were drawn from the venous plexus of the hind

flippers at approximately 5, 20, and 28 h after administration of

the isotope. During this time, animals were fasted and kept on

deck. Blood samples were allowed to clot, and the plasma was then

obtained and kept frozen at -70 0 C until analysis.









Laboratory Analyses

Water was obtained from plasma samples by distillation,

using the method proposed by Oftedal and Iverson (1987). I heated

each sample in 10-mL distillation tubes and collected the water in

a side arm tube immersed in a mixture of ethyl alcohol and dry

ice. The concentration of deuterium oxide in the water samples

was then determined through mass ratio spectrophotometry (Speakman

1997).



Calculations

Concentrations of D20 in plasma were used to determine water

pool size (P) of seals. After log transformation of the plasma

concentrations of D20, I regressed them against time after

administration of the isotope, to calculate D20 concentration at

time of administration (Figure 5.1). This approach prevents the

overestimation of water pool size that occurs when using the

actual concentration of D20 obtained after an equilibration time

of 3-4 hours (Oftedal and Iverson 1987, Speakman 1997). Then, I

calculated water pool size using the formula:

Water pool size (Po) = [D20] at time of administration (Co)

D20 administered

Water pool size (P) was used to estimate lean body mass

(LBM) using a ratio of 0.703 (P:LBM) determined by carcass

analysis of adult harp seals (Gales et al. 1994). Body fat was

determined as the difference between body mass and lean body mass.

Protein was also estimated using the data obtained from carcass









analysis. That study found that 25.7% of LBM of adult harp seals

was protein (Gales et al. 1994). I estimated energy content of

the body using the energy equivalencies of 38.91 kJ/g for fat and

of 23.64 kJ/g for protein (Oftedal et al. 1987b).


Results

On average, adult harp seals were 43.6 2.26 % water, 37.9

+ 3.22 % fat, and 15.9 0.83 % protein, and had an energy density

of 18.5 1.06 MJ/kg (Table 5.1). Although body fat increased

with body mass (F1,15 = 49.19, P < 0.0001), the proportion of body

fat did not change in relation to body mass (F1,15 = 3.3, P <

0.0926; Figure 5.2).

Although seasonal variations in body composition were

apparent, they were not significant (F3,14 = 3.08, P = 0.0901), and

the only significant factor was "seal" (F3,14 = 10.73, P = 0.0035).

Changes in body mass were not only a product of changes in fat

depots, but they were also related to large changes in lean body

mass. Although minimal body mass occurred during winter, the

lowest proportion of body fat was observed during spring (Figure

5.3). Although body mass decreased more or less linearly from

winter to summer, lean mass changed little from winter to spring,

but changed rapidly from spring to summer. This was also

reflected in that the average energetic density of body tissues

increased from spring to summer (Figure 5.4).









Discussion

The four adult harp seals had different body compositions.

The female BAB, and the male TYL had large fat depots for most of

the study period, with a maximum of 63 and 46.7% body fat,

respectively. However, body composition of these captive seals

was comparable to that of wild seals studied through dissection

and carcass analysis (Gales et al. 1994). In the present study

body fat during spring averaged 31%, while it averaged 33.2% in

the wild adult seals studied during the same season (Gales et al.

1994).

The method of isotope dilution has been proven to produce

accurate estimations of body composition. Comparisons of total

body water content with results from proximate composition

analyses of carcasses, have shown that the differences between the

two approaches is less than 2% (Lydersen et al. 1992, Oftedal et

al. 1993).

This study is the first to show that the seasonal variation

in body mass of harp seals is not solely the result of changes in

the size of fat depots throughout the year. Given that mass

changes have a different make-up during the different seasons, the

same levels of body mass changes will imply different rates of

energy deposition or mobilization.










Table 5.1. Body composition of adult harp seals throughout the


year cycle. The amount of
given in absolute (kg) and
parentheses).


each of the different components is
relative terms (percentage, in


Body Lean Energy
Seal Season mass body Water Fat Protein Other Density
(kg) mass (MJ/kg)
ELM Fall 127.4 91.8 64.6 35.6 23.6 3.7 15.2
(72.1) (50.7) (27.9) (18.5) (2.9)


Winter 150.2 97.3 68.4 52.9 25.0 3.9
(64.8) (45.5) (35.2) (16.6) (2.6)
Spring 139.0 100.3 70.5 38.7 25.8 4.0
(72.1) (50.7) (27.9) (18.5) (2.9)


Summer 112.6 78.4
(69.6)


TYL Fall


55.1
(48.9)


34.2
(30.4)


20.1
(17.9)


3.1
(2.8)


153.2 81.7 57.4 71.5 21.0 3.3
(53.3) (37.5) (46.7) (13.7) (2.1)


Winter 188.8 101.9
(54.0)


71.6
(37.9)


86.9
(46.0)


26.2
(13.9)


4.1
(2.2)


Spring 169.6 103.6 72.8 66.0 26.6 4.1
(61.1) (42.9) (38.9) (15.7) (2.4)


Summer 133.1 70.9
(53.3)
VIR Fall 124.4 72.5
(58.3)
Winter 149.0 116.8
(78.4)
Spring 106.4 91.4
(85.9)
Summer 107.5 70.2
(65.3)
BAB Winter 285.8 139.0
(48.7)
Spring 149.4 85.3
(57.1)


49.9
(37.5)
51.0
(41.0)
82.1
(55.1)
64.2
(60.4)
49.4
(45.9)


62.2
(46.7)
51.9
(41.7)
32.2
(21.6)


18.2
(13.7)
18.6
(15.0)
30.0
(20.1)


2.8
(2.1)
2.9
(2.3)
4.7
(3.1)


15.0 23.5 3.7
(14.1) (22.1) (3.4)


37.3
(34.7)


97.8 146.8
(34.2) (51.3)
60.0 64.1
(40.2) (42.9)


18.0
(16.8)
35.7
(12.5)
21.9
14.7)


2.8
(2.6)
5.6
(1.9)
3.4
(2.3)


Summer 139.2 51.5 36.2 87.7 13.2 2.1
(37.0) (26.0) (63.0) (9.5) (1.5)


17. 6


15.2


16.1


21.4


21.2


18.9


21.4


19.8


13.2


10.7


17.5


22.9


20.2


26.8












-6.24


0
(N
0

0)
0J


-6.26


-6.28


-6.30 1 1
0 5 10 15 20 25 30
Time after administration (h)








Figure 5.1. Methodology used to estimate concentration of
deuterium oxide at time of administration (Co). This method
avoids the overestimation of total body water that occurs when
the concentration determined from the first blood sample is used
as an estimation of Co.








150-

125-

100-
01-%%75


50-

25-

0

60

50*


30-

20

10


Y= -37.5 +0.646 X
r = 0.79, P< 0.0001



V


A0


I


0 S
A V


A
0


100


00


150


200


V BAB
N TYL
A VIR
* ELM


250


Body mass (kg)




Figure 5.2. Relationship between body mass and absolute amount of
body fat (top graph), and proportion of body fat (bottom graph)
of four captive adult harp seals (Pagophilus groenlandicus).


0


300


1 0










180

150-


-'120

Cn 90-
CU
b60


30

0


Ir


1 Water
Fat
11111 Protein
Other


I


I. h i &


Fall


Winter


Spring


Summer


Figure 5.3. Seasonal changes in the components of the body and
proportion of body fat of captive adult harp seals (Pagophilus
groenlandicus).


60

*50

*40o,.



20


10







180
CM
160
c 140
120-

120
10)
-~1001
( clo
1 ) 80
E 60

4000

2 -- 3000
W 2000

24
M 20
LC: 16
12


500
La) 0
':CU-500-
0-1000,,

Fall Winter Spring Summer
Figure 5.4. Seasonal changes in body composition and energy
content of captive adult harp seals (Pagophilus groenlandicus).
















CHAPTER 6
ACTIVITY LEVELS AND ENERGETIC COST OF ACTIVITY IN HARP SEALS


Introduction

Activity is an important component of the energy budget of

animals. Locomotion in pinnipeds is aided by adaptations that

reduce drag such as a streamlined body shape, and the power output

needed for forward motion. Although the metabolic rate of

terrestrial mammals increases linearly with speed, a curvilinear

increase has been observed in seals. This increase in metabolic

rate correlates with the curvilinear increase in drag as a

function of speed (Williams and Kooyman 1985). Despite the effect

of drag, pinnipeds use less energy for locomotion than terrestrial

mammals of similar size, due in part to the absence of postural

costs (Schmidt-Nielsen 1972, Feldkamp 1987).

Phocid seals propel themselves by alternate lateral sweeps

of the hind flippers in a sculling action in conjunction with

oscillations of the body (Tarasoff et al. 1972, Fish et al. 1988).

The amplitude of the stroke does not change with swimming speed,

and thus speed is linearly related to stroke frequency (Davis et

al. 1985, Fish et al. 1988)

My objectives were to estimate the influence of activity on

energy expenditure and food intake of harp seals, and to explore

the influence of activity levels on the observed seasonal changes









of energy expenditure and food intake. This study was conducted

in collaboration with Valerie Moulton, Master's student at the

Biology Department, Memorial University of Newfoundland. She

focused her study on the influence of weather and social

interactions on activity levels of captive harp seals.


Material and Methods

Activity levels of harp seals were measured with simplified

Mk6 time-depth recorders (Wildlife Computers, Redmond,

Washington). These recorders detected changes of more than 450 in

their position with respect to the horizontal and vertical planes.

In addition, the recorders were fitted with conductivity pins that

detected if the animal was in or out of the water. Data collected

every minute on the minute was number of tilts (> 450) and dry or

wet state.

The deployment of the activity recorders along the dorsal

line between the second and third thirds of the body (Figure 6.1)

allowed detection of hind flipper strokes used by phocid seals for

propulsion. Although stroke frequency provides a measure of the

speed of a particular seal, it does not provide a direct

assessment of the energy expended in locomotion because metabolic

rate increases exponentially with swimming speed (Williams and

Kooyman 1985). Oxygen consumption of harbor seals swimming in an

aquatic flume was proportional to swimming speed raised to the

1.42 power (Davis et al. 1985). To use tilt frequency measured by

the activity recorder as an estimation of the energy spent in

locomotion, I raised tilts per minute to the 1.42 power before









including this factor in the multivariate linear models used to

detect the influence of activity on energy budgets.

I used the hourly average of tilt frequency for each of the

animals for the analysis of circadian rhythms. I calculated

average tilt frequency and time spent on deck (out of the water)

for each of the periods between consecutive weightings to explore

the relationship between activity and energy budgets. In

addition, I calculated daily mass change (DMC, g/d) as the

difference between two consecutive weighings, divided by the days

elapsed between them. Daily food intake during each of the

periods between consecutive weighing was averaged and multiplied

by the energetic content of herring, and by its digestive

efficiency (Lawson et al. 1997) (Table 2.1) to estimate digestible

energy intake, DEI. To determine if activity changed throughout

the year in a significant manner, I conducted ANOVAs using

"season" and "seal" as factors.


Results

Circadian rhythms were apparent for the activity levels of

harp seals. Levels of activity changed through the day in a

consistent manner for all the seals studied (Figure 6.2).

Activity tended to increase around midday, when the seals were

fed. To determine if this circadian pattern had some relation

with daylength, I regressed the coefficient of variation

calculated for each day using mean of tilts per hour against

photoperiod. The pattern of circadian variation in activity did









not change in relation to photoperiod. There was no clear pattern

of changes in activity level among seasons (Figure 6.3).

I used multivariate linear models and regression analyses to

determine if activity level, as measured by the activity data

recorders, had a significant effect on the energy budget of

captive harp seals. I first tested for the effect of the factors

"seal" and "season" on daily mass change with a model that also

included energy intake, body mass, proportion of time spent on

deck (out of the water), and mean number of tilts raised to the

1.42 power (see Methods). The factors "seal" and "season", and

the regressor body mass had no effect on the rate of mass change

(F8,258 = 1.74, P = 0.09; F3,258 = 2.61, P = 0.0522; F1,258 = 3.16, P =

0.077, respectively). The proportion of time spent on deck

explained 2.4% of the total variation on daily mass change and had

an effect on the energy budget (F1,258 = 4.61, P = 0.0328). Energy

intake explained 34.6% of the observed variation in daily mass

change (F1,258 = 67.21, P < 0.0001) Activity level, measured as

mean number of tilts raised to the 1.42 power, explained 3.2 % of

the total variation observed in daily mass change (F,258 = 6.25, P

< 0.0131). The relationship between activity and daily mass

change is presented in Figure 6.4, by plotting the residuals of

the linear model of daily mass change against all the factors

mentioned above except tilts per minute, against tilts per minute.


Discussion

The use of activity recorders provides information on the

general level of activity of seals. However, the present









configuration of the system has major drawbacks. A major

logistical limitation is that the sensor cannot be deployed too

caudal on the animal's back to avoid its removal by the animal

with its mouth. A more posterior deployment would ensure that the

signal more accurately reflects the strokes used for propulsion by

phocid seals. Another limitation of the system is that it cannot

discern between tilts performed along the different axes. For the

use of this device to estimate stroke frequency, it would be

advantageous to limit the recording only to tilts performed in

relation to the vertical axis. The fact that this was one of the

first trials of this new technology precludes me to discuss my

results with those of other investigators.

The measurement of stroke frequency can be used as an

estimator on swimming speed because they are related linearly in

phocid seals. An analysis of the data for three species provided

in published reports (Davis et al. 1985, Fish et al. 1988) shows

that swimming speed increases linearly with stroke frequency

(Figure 6.5)

Although locomotion can be energetically expensive, its

impact on the energy budget is generally low. It has been

estimated that locomotor energy expenditure in terrestrial mammals

requires less than 2% of the total field metabolic rate, and that

this value is more or less independent of body mass (Altmann

1987). The fact that aquatic locomotion is less energetically

expensive than terrestrial locomotion (Schmidt-Nielsen 1972,

Feldkamp 1987) allows the inference that locomotion in phocid









seals also constitutes a small fraction of the overall energy

budget.

The observation that the circadian rhythm of activity did

not change with length of day points to the possibility that the

increase in activity at midday was not related to the day/night

phase, but was an artifact introduced by the maintenance

activities performed by the seals' keepers. These activities

included cleaning of decks and tanks, removing ice, and feeding

the animals for two hours. A concurrent study demonstrated that

seals spent less time resting on deck when disturbed, thus

increasing time spent swimming (Moulton et al. In Press).

Differences in energy expenditure of harp seals between

seasons were not due to differences in the levels of activity.

Activity changed between seasons with no common pattern among the

seals studied, whereas energy expenditure did (chapter 2).




















































Figure 6.1. Diagram of a phocid seal swimming. These animals use
lateral alternating movements of their hind flippers and
posterior part of the body to produce thrust. The location of
the activity recorder used to detect lateral strokes is marked by
the shaded circle.









8-
6-
0) 4
2
0
8
C- 6-

2
Eo
8
i. 6
4
2


8-

4-
2-
0
m 8-
-6-
4-
2-
0


BAB






ELM


MIC


TYL


VIR


0 6 12 18 24


0 6 12 18 24

Time of day (hour)
Figure 6.2. Activity levels of nine harp seals, Pagophilus
groenlandicus, measured as tilts per minute in relation to time
of day.

































I I I I
Fall Win Spr Sum


Fall Win Spr Sum


S


easo n


Figure 6.3. Changes in activity levels of captive harp seals,
Pagophilus groenlandicus, measured as tilts per minute in
relation to season.


BAB






ELM






VIR


(1)


4-



E






C_
.-










3000

2000 .o
0 o
0 0 S


- I -1000 0
Cr)
-2000 Y =284.7-16.86 X
r 2 = 0.06, P < 0.0001
-30001 1
0 10 20 30 40

(Tilts/min)1 -42




Figure 6.4. Influence of activity on daily mass change of
captive harp seals, Pagophilus groenlandicus. The plot
represents the relationship between an estimator of energy spent
in locomotion [(tilts/min) .42] and the residuals of the linear
model relating daily mass change (DMC,g) and the variables seal,
season, mass (g), energy intake (kJ/day), and time spent on deck
(%).