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Group Title: Bulletin of the Florida Museum of Natural History
Title: Body mass and skull measurements in four jaguar populations and observations on their prey base
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Permanent Link: http://ufdc.ufl.edu/UF00095784/00001
 Material Information
Title: Body mass and skull measurements in four jaguar populations and observations on their prey base
Series Title: Bulletin - Florida Museum of Natural History ; volume 39, number 6
Physical Description: p. 195-219 : ill. ; 23 cm.
Language: English
Creator: Hoogesteijn, Rafael, 1953-
Florida Museum of Natural History
Publisher: Florida Museum of Natural History, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1996
Copyright Date: 1996
Subject: Jaguar   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 217-219).
General Note: Cover title.
Statement of Responsibility: Rafael Hoogesteijn and Edgardo Mondolfi.
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Bibliographic ID: UF00095784
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 36006888
issn - 0071-6154 ;

Table of Contents
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    Literature cited
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    Back Cover
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Full Text


of the



Rafael Hoogesteijn and Edgardo Mondolfi



published at irregular intervals. Volumes contain about 300 pages and are not necessarily completed in
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Publication date: September 30, 1996

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Rafael Hoogesteijn' and Edgardo Mondolfi2


Body mass and nine skull measurements of two floodplain (Pantanal and Llanos) and
two forest (Amazon and Central America) jaguar (Panthera onca) populations, were
analyzed to compare them, relate their morphometric dimensions to preybase and latitude,
and examine the relationship with their subspecies status. Analyzing data from males and
females separately, jaguar at all sites differed significantly for most variables studied, with
the exception of rostral breadth, maxillary teeth row length, and pterygoid fossa breadth for
both sexes, and postorbital breadth for females, which were either not or only weakly
significant. Individuals from the floodplain populations were consistently larger in almost
all parameters than the samples from the forest sites. The difference is independent of the
subspecific status. Comparisons among the biomass values of prey taken at each site were
also consistently higher for floodplain populations. Jaguar skull size and body mass seem to
be more related to biomass of prey taken than to latitudinal location. The differences found
in these four populations and the high number of Central American subspecies suggest that
a revision of subspecies validity is needed. The reduction in the subspecies number is not
only important from a taxonomic point of view but also from an ecological and
conservationist one. The increase of our understanding of the phylogenetic heritage and
morphological and ecological variation within the species is a priority for conservation.


Se compar6 peso corporal y nueve medidas craneanas entire dos poblaciones de jaguar
(Panthera onca) de sabanas inundables (Pantanal y Llanos) y dos poblaciones de jaguar de
selva (Amazonas y America Central). Analizando machos y hembras por separado, los
animals provenientes de los diferentes sitios estudiados difirieron significativamente en

SDepartment of Wildlife Ecology and Conservation, Newins Ziegler Hall, University of Florida, Gainesville FL 32611 U.S.A..
2 Institute de Zoologia Tropical. Facultad de Ciencias, Universidad Centra de Venezuela, Caracas. Venezuela.

HOOGESTEIJN, R., AND E. MONDOLFI. 1996. Body mass and skull measurements in four jaguar
populations and observations on their prey base. Bull. Florida Mus. Nat Hist. 39(6):195-219.


todas las variables estudiadas, con la excepci6n de ancho del rostrum, longitud de la series
dental superior (canino al PM3) y ancho de la fosa pterigoidea en ambos sexos; y ancho
post-orbitario en las hembras. Los jaguars del Pantanal y Llanos fueron consistentemente
mas grandes que los jaguars de selva en casi todos los parkmetros estudiados. Estas
diferencias fueron independientes del status subespecifico. Las comparaciones de la
biomasa de press consumidas en cada sitio indicaron que la biomasa fue consistentemente
mayor para las poblaciones de sabanas inundables. El tamaflo corporal y del crineo de
jaguars parece estar mas relacionado con la biomasa de press capturadas que con la
localizaci6n latitudinal. Las diferencias encontradas entire estas cuatro poblaciones y la gran
cantidad de subespecies centroamericanas, sugiere la necesidad de revisar la validez de las
categories de subespecies.


The jaguar (Panthera onca) is the largest felid of the Americas,
presently occurring from Mexico to northern Argentina. The jaguar survives
in many different types of habitats such as semiarid areas in Mexico,
semideciduous and thorn forests in the Paraguayan Chaco, humid multistrata
evergreen forest in the Amazon, and cloud forest in the Andean foothills.
Except for anecdotes and notes on its natural history, little was known of its
ecology and biology until 1970. Research conducted in the last three decades
has revealed its great adaptability to different habitats and prey bases, in
addition to great variations in body size between areas (summarized in
Hoogesteijn and Mondolfi 1993a).
Our preliminary analyses (Hoogesteijn and Mondolfi 1993b) suggested
that the floodplain populations (living in the Pantanal and Llanos) had greater
body sizes (head and body length and tail length), body mass, and skull
measurements (skull and width) than jaguars from other parts of Venezuela
and Central America. In this study we examined a larger sample and
compared the body mass and skull size of jaguars from two forest areas vs.
jaguars from two floodplain areas, relating those dimensions to preybase and


The authors express their gratitude to Colin Chapman and Michael Moulton who
helped with the statistical analyses. John Eisenberg, S. David Webb, and Melvin Sunquist
provided important advice and bibliographical material. John Seidensticker, Peter
Crawshaw, Lauren Chapman, Charles A. Woods, and John Polisar reviewed the manuscript
and made valuable suggestions.


Data Sources

Data on body mass and skull measurements of jaguars from the Llanos
and the Guayana region of Venezuela were collected during 14 years of
veterinary professional practice. Reliable Venezuelan sport hunters also
cooperated by weighing and measuring jaguars killed because of persistent
cattle killing. They also checked stomach contents and lent the skulls for
measurements. Data on head, body, and tail length were available but not
used in this study, because there is a high variation, depending upon who did
the measurement and whether the measures were taken along the curves or
"between pegs" (Almeida 1976). Body mass and skull measurements data
were more reliable. Skull measurements were checked by other researchers to
reduce error.
In this study, the total length of skull is the distance from the anterior
edge of the premaxillar bone to the rear point of the occipital crest. Skull
width is the maximum distance between the outer edges of the zygomatic
arches. A skull index was obtained by adding the two previous measurements
for each skull. Skulls with only one of these measurements (length or width)
were deleted from the database. We included data from Almeida (unpubl.
data), for some skulls where only the skull index was available. Condilobasal
length was measured between the anterior edge of the premaxillar bone and
the posterior edge of one of the occipital condyles. Length of the upper tooth
row was measured between the anterior edge of the upper canine and the
posterior edge of the upper carnassial. The maximal length of the carnassial
crown was also measured. Rostral breadth was measured behind the canines.
Infraorbital and postorbital breadths were measured at the narrowest points
between and behind the orbits respectively, and the breadth of the pterygoid
fossa was transversely measured at the mid point (see Fig. 1).
Published measurements were pooled with the above unpublished data
and separated into four geographical areas. The sample titled Central
America consisted of data from Mexico (Pocock 1939; Aranda 1992), Costa
Rica (Pocock 1939; Goodwin 1946), Guatemala (Pet6n) and El Salvador
(Pocock 1939), Belize (Rabinowitz 1986; Rabinowitz and Nottingham 1986),
and the northern Colombia's Magdalena Valley (Pocock 1939). All these data
were considered as one forest group. This area is inhabited by five different
subspecies (P. onca arizonensis, P. o. veraecrucis, P. o. hernandesii, P. o.
goldmani, P. o. centralis), following Nelson and Goldman (1933). Pocock

\ '* / \"7 i o3 / a

!- j I

Figure 1. Measurements (in mm) of jaguars were taken as (A) skull length, (B) skull width, (C) rostral breadth, (D) 0
interorbital breadth, (E) postorbital breadth, (F) condylobasal length, (G) upper carnassial tooth length, (H) upper
maxillary tooth row length, and (I) pterygoid fossa breadth. (In the jaguar the last molar is placed medially to the


(1939) and Seymour (1989) suggested that these five subspecies could be
reduced to only one (P. o. hernandesii).
The second sample titled the Amazon block consists of animals from the
subspecies P. onca onca, and from a second subspecies of dubious validity
(P. onca peruviana) (Pocock 1939). These data are from Surinam (Pocock
1939; Husson 1978 ), from the Brazilian Amazon (Pocock 1939; Almeida,
unpubl. data) and from the states of Bolivar and Amazonas in Venezuela's
"Guayana region" (Pocock 1939; Hoogesteijn and Mondolfi, unpubl. data).
All these data were considered as a second forest group.
The third sample consists of jaguars from the Llanos or floodplains of
Venezuela (Hoogesteijn and Mondolfi 1993b, this study). The Llanos of
Venezuela is a large, low lying savanna region that comprises much of the
northern and western regions of the Orinoco River drainage basin in
Venezuela and Colombia (Thorbjarnarson 1991). The jaguar population
inhabiting this region is currently included in the same subspecies as the
Amazon jaguar (P. onca onca).
Jaguars in the fourth sample come from the Pantanal or floodplains of
southwestern Brazil and the bordering area of Paraguay and Bolivia. These
data came from Allen (1916), Pocock (1939), Almeida (1976, unpubl. data),
and Crawshaw and Quigley (1984). Measurements of some skulls from the
Chaco of Argentina and Paraguay, and Rio Grande do Sul, Brazil, also were
included in this group (Pocock 1939; Cabrera 1961; Ximenez and Silva
1979), since they belong to the same subspecies, P. onca paraguensis,
(following Seymour 1989). The few skulls (5 males, 1 female) from the
Chaco are smaller than those from the Pantanal, so the Pantanal skull size
means are slightly reduced, rather than enlarged by the inclusion of these
skulls. The data reported in the geographical areas included here, and their
bibliographical sources are shown in Table 1.
The data in the literature that were not included are: (1) Some skull
measurements of Mexican jaguars reported by Aranda (1992), and of
Belizean jaguars reported by Rabinowitz and Nottingham (1986). These
authors did not report the individual skull measurements, but only the means
and standard deviations (S.D.) for males and females. These data are
compared in the discussion section. (2) Two body mass measurements of
very small Peruvian forest jaguars (both males in apparently good condition
at 31 and 37 kg) taken by Emmons (1987), and some mass or skull
measurements from localities that could not be clearly assigned to forest or
floodplain areas of Peri and Bolivia (Pocock 1939) or Brazil (Crawshaw


Table 1. Site groups and references of jaguar mass and skull measurements utilized
in the statistical analyses.

Forest Areas
Site 1, Central America,
M6xico (Aranda 1992; Pocock 1939)
Belize (Rabinowitz 1986; Rabinowitz & Nottingham 1986)
Costa Rica (Goodwin 1946; Pocock 1939)
Guatemala, Pet6n (Pocock 1939)
El Salvador (Pocock 1939)
Colombia, Magdalena Valley, (Pocock 1939)

Site 2, Amazon Block,
Surinam (Husson 1978; Pocock 1939)
Brazil, Northern and Lower Amazon, (Pocock 1939; Almeida unpub.)
Venezuela, Guayana Region, (Pocock 1939;
Hoogesteijn & Mondolfi 1993a, b; this study)

Floodplain Areas
Site 3, The Llanos of Venezuela
Venezuela, States Apure, Gudrico, Cojedes,
Barinas, (Hoogesteijn & Mondolfi 1993a, b; this study)

Site 4, The Pantanal
Brazil, Paraguay (Allen 1916; Pocock 1939;
Almeida unpub.; Crawshaw & Quigley 1984)

The Chaco
Argentina, Paraguay, Southern Brazil (Pocock,
1939; Cabrera 1961; Ximenez & Silva 1979)

1992). (3) Data reported by Nelson and Goldman (1933), in their jaguar
subspecies revision, since they are repeated in Pocock's (1939) work. (4)
Following Pocock (1939), two skulls from Mexiana Island, Maraj6, Brazil,
since they only include the zygomatic width measurement.
A total of 128 body mass measurements, 156 skull lengths and widths,
and 162 skull indices were included in the comparison of two forest samples
(Central America and the Amazon) and two floodplain samples (the Llanos


and the Pantanal) (see Tables 2-6). The number of skulls measured for the
other variables are reported in Tables 7-9. A copy of the complete data set is
available from the senior author.
To avoid the effects of age within and between samples (Fernandez and
Lope 1994; Gay and Best 1996) subadults were eliminated from the analyses.
Data previously summarized by Oliveira (1992), in the form of the mean
body mass of vertebrate prey index (MWVP), were used to compare the prey
taken by jaguars in forest and floodplain areas. Only the results mentioned by
this author were used, since we (and also Crawshaw 1995), found
discrepancies between the results from the MWVP calculations obtained from
the same data sets by different authors (Iriarte 1988; Oliveira 1992;
Jorgenson and Redford 1993). This index is calculated as the geometrical
mean obtained by summing the products of the numbers of individual prey
times their loge transformed mass, and divided by the total number of prey.
An acknowledged shortcoming in comparing these studies is that the food
habits were often quantified on the basis of unequal sampling efforts
(sometimes with a small number of samples), in different seasons, or from
different sources (feces, kills, or stomach contents), and it also depends on
knowing prey size (adult or young prey), but such comparisons are useful to
infer the differences among the areas included and their preybases. The
inclusion or exclusion of domestic stock in the prey also was considered.

Statistical Analysis

Data of body mass in kilograms and skull length, width, index
(length+width), condylobasal, carnassial, and maxillary teeth row length and
the rostral, interorbital, postorbital, and pterygoid fossa breadth (all in
millimeters) were analyzed by analyses of variance using SPSS # 6.0 and the
SAS statistical package. Analyses were done separately for males and
females to determine the site effect on each of the measurements previously
mentioned. A separate analysis was done for the skull index including the
site, sex, and sex x site interaction effects, with all the data of males and
females combined. Differences between means were determined by Scheffe's
multiple range test with a significance level of .05.


Table 2. Male jaguar mass (kg) by site.

Site n Mean S.D. Constant

Llanos 26 104.5 9.6 +121
Pantanal 24 99.5 11.2 +7
Amazon 9 83.6 9.7 -8
C. America 12 56.1 5.7 -35

Total 71 92.0 92.0

*The constant represents the difference in means mass by site compared to the mean mass of all sites
combined. Two groups with lines at the same level do not differ significantly.

Site Effect on Body Mass

Site effects for body mass (kg) were highly significant for males
(f=76.49, p<.001). The Llanos group had the highest mean, followed by the
Pantanal group. There were no significant differences between the two
floodplain groups, but they differed significantly from the two forest groups,
which also differed significantly from each other (Table 2). Site effects were
also highly significant for females (f=42.82, p<.001). The Pantanal group of
females had the highest mean, followed by the Llanos group and Central
America. Amazon females were not included in the body mass analysis
because of a small sample size. All three groups differed significantly from
each other, the two floodplain groups were the heaviest (Table 3).

Site Effect on Skull Measurements

Site effects of skull length were highly significant in males and females
(f-44.8, p<.001 and f=24.76, p<.001). For males, there were no significant
differences between the two floodplain groups. Both had higher means and
were significantly different from the two forest groups (Amazon and Central


Table 3. Female Jaguar mass (kg) by site.*

Site n Mean S.D. Constant

Pantanal 18 76.7 9.0 +10
Llanos 31 66.9 9.7 +1
C. America 8 41.4 5.1 -25

Total 57 66.4 66.4

*Same observations as in Table 2. See text for comments.

America), which also differed between themselves, and had lower means. The
number of observations and differences between means for males and females
can be seen in Table 4. For females, the descending order was the same as in
the males. The two extreme groups, Pantanal and Central America differ
from the others, and the Llanos and the Amazon had no significant difference
between them (Table 4).
Differences in skull width by site were highly significant in males and
females (f= 41, p<.001 and f=15.85, p<.001 respectively). For males, there
were no significant differences between the two floodplain groups (Pantanal
and Llanos), which had the highest means, but they differed significantly
from the two forest groups (Amazon and Central America), which did not
differ between themselves (Table 5). For females, the descending order is the
same as in males. The mean for the Pantanal females was higher and
significantly different from the other groups. There was no significant
difference for the mean of the Llanos and the Amazon. The Llanos differed
significantly from Central America and the two lowest groups, Amazon and
Central America, did not differ between themselves (Table 5).
Turning to the skull index, site effects were highly significant in males
and females (f=52.91, p<.001 and f=22.81, p<.001). Statistical differences
between the four male group means were the same as described for the males
skull length (Table 6). The difference between the means of the female groups
followed the same tendency as described previously for female skull width
(Table 6).


Table 4. Male and female jaguar skull lengths (mm) by site

Site n Mean S.D. Constant

Pantanal 48 290.5 13.9 +091
Llanos 23 289.6 11.3 +081
Amazon 19 262.6 13.1 -19
Central Amer. 07 243.6 07.9 -38
Total 97 281.4 281.4
Pantanal 28 257.6 11.3 +10
Llanos 23 242.8 09.3 -051
Amazon 04 237.0 10.9 -111
Central Amer. 04 215.2 12.3 -32
Total 59 247.6 247.6

*Same observations as in Table 2. See text for comments.

Table 5. Male and female jaguar skull widths (mm) by site.

Site n Mean S.D. Constant

Pantanal 48 194.2 8.7 +061
Llanos 23 194.1 9.1 +051
Amazon 19 175.9 7.5 -13 |
Central Am. 07 166.4 6.4 -22 |
Total 97 188.6 188.6
Pantanal 28 172.5 6.5 +5
Llanos 23 166.1 7.5 -1
Amazon 04 160.2 9.0 -71 |
Central Am. 04 148.7 8.0 -19 |
Total 59 167.6 167.6

*Same observations as Table 2. See text for comments.


Table 6. Male and female jaguar skull indices (mm) by site.*

Site n Mean S.D. Constant

Pantanal 51 485.2 20.7 +141
Llanos 23 483.7 17.8 +131
Amazon 19 438.5 19.5 -32
Central Amer. 07 410.0 13.5 -61
Total 100 470.7 470.7
Pantanal 31 428.6 6.5 +13
Llanos 23 408.9 7.5 -061
Amazon 04 397.2 9.0 -1811
Central Amer. 04 364.0 8.0 -51 |
Total 62 415.1 415.1

*Same observations as Table 2. See text for comments.

Table 7. Male and female jaguar condylobasal lengths by site (mm)*.

Site Male Means Female Means
n = 72 n = 42

Pantanal 252.321 227.351
Llanos 251.301 219.981 |
Amazon 235.31 209.90
Central America 223.14 194.70

*Same observations as Table 2. See text for comments.


Table 8. Male and female jaguar upper carnassial tooth lengths (mm) by site.*

Males (n = 73) Females (n = 41)

Site Means Site Means

Pantanal 29.251 Pantanal 27.69
Llanos 28.261 Amazon 26.551 I
Amazon 28.061 Llanos 26.30 I
Central America 26.56 Central America 24.82 I

*Same observations as Table 2. See text for comments.

The differences in mean condylobasal length were highly significant for
males and females (f=15.28, p<.001 and f=14.68, p<.001). The males
followed exactly the same tendency as described for skull length. The number
of observations and differences between means can be seen in Table 7. In
females the descending order was the same as in the males, but there were no
differences in the means between the Llanos and the Amazon females (Table
Differences in upper carnassial tooth length by site, were highly
significant for males and females (f=10.9, p<.001 and f=5.24, p<.004). The
order of magnitude in the males was similar as described previously for the
other skull measurements, but the only group that differed significantly from
the others and had the smallest mean was the Central American one (Table
8). For the females the order of magnitude is slightly different, the group with
the highest mean still was the Pantanal, but followed by the Amazon and the
Llanos (which did not differ between themselves). The Central American
group, also had the lowest mean, but it was not significantly different from
the Llanos and Amazon means (Table 8).
In summary, mean skull length, width, index, condilobasal length in
males and females and upper carnassial tooth length in males were highest in
the floodplain groups and lowest in the forest populations.
Differences in interorbital breadth were surprisingly different. Site
effects were significant for males (f=3.44, p<.022) and highly significant for


females (f-12.79, p<.001). In males the order was Llanos, Central America,
Pantanal, and Amazon, with no differences between the first three and the last
three groups (Table 9), so the Central American group had the second largest
mean in males. Central American females had the largest mean, statistically
different from the other three groups, which did not differ between themselves
(Table 9). This result, more consistent for the females, shows that despite
having a smaller and narrower skull, Central American jaguars have a
relatively broader frontal bone area at the interorbital breadth measurement
For upper maxillary tooth row length, rostral, pterygoid fossa, and
postorbital breadth, site effects were not significant or only slightly so. Also
the Scheffe's multiple range test was unable to detect significant differences
between the group means.

Two-Way Interactions of Sex-by-Site

The complete data of skull indices of males and females were included
and combined in an analysis including the effects of sex, site, and the two-
way interaction of sex x site. All effects were highly significant, indicating
that the relative differences between sexes were not the same in the different
sites. The Pantanal and Central America groups have a difference of 30-31%

Table 9. Male and female jaguar interorbital breadths (mm) by site.*

Males (n = 68) Females (n = 40)

Site Means Site Means

Llanos 55.921 Central America 57.39
Central America 54.731 I Llanos 48.261
Pantanal 52.151 I Pantanal 45.38 I
Amazon 49.07 I Amazon 44.251

*Same observations as Table 2. See text for comments.


in body mass between males and females; the sex difference for the Llanos is
56%. Also the differences for skull measurements between males and females
were greater for the Llanos (between 17 and 19%) compared with the other
groups, where differences oscillated between 10% and 13%. There is
apparently a higher degree of sexual dimorphism in the Llanos population
than elsewhere (Table 10) .

Mean Mass of Vertebrate Prey Index

The values of the MWVP index are shown in Table 11. MWVP was
lowest for forest jaguars. The first value was calculated from Aranda's
(1992) work, with 18 fecal samples collected in YucatAn, M6xico. The
principal prey was collared peccary (Tayassu tajacu), coati (Nasua nasua),
and red brocket deer (Mazama americana). These species constituted 83
percent of the total prey in this area, and had a MWVP value of 5.6 kg. The
second MWVP value of 5.4 kg represents an average of two studies done in
Belize (Rabinowitz and Nottingham 1986; Watt 1987). In one, 228 fecal
samples were analyzed and the principal prey species were armadillo
(Dasypus novemcinctus), paca (Agouti paca), collared anteater (Tamandua
mexicana), and red brocket deer, species which constituted nearly 80 percent
of the diet. In Watt's study 74 fecal samples were analyzed. The principal
prey species were also armadillo, paca, small rodents, and collared peccary,
species that constituted 60 percent of diet. This sample also included other
smaller mammals and a larger proportion of iguanas and snakes. Watt's study
was done in the same place but at a later date and, as suggested by this
author, with a population of younger jaguars that were preying upon smaller
species of prey.
The third MWVP value was calculated from data reported by Emmons
(1987) from Cosha Cachu, Man6i, Peri. Based on an analysis of 25 fecal
samples, the MWVP value was 10.7 kg, which is larger than the two Central
American sites. Principal prey consisted of large aquatic reptiles, large
mammals such as collared peccary and brocket deer, large rodents (paca and
agouti), and birds, all of which comprised 81 percent of the diet. The
combined MWVP average for these three forested areas was 5.8 kg.
In comparison, MWVP for the floodplain jaguars was much higher. For
two Brazilian studies, the MWVP only for natural prey (without cattle and
sheep) was 32.4 kg. The first sample consisted of 59 kills from the Pantanal,
Mato Grosso, Brazil (Crawshaw and Quigley 1984). The principal natural


Table 10. Morphometric differences in mass and skull dimensions between male and female jaguars (kg and mm).


Mass Skull Length Skull Width Skull Index

Site n kg % n mm % n mm % n mm %

Pantanal 42 23 30 76 33 13 76 22 13 82 57 13
Llanos 57 38 56 46 47 19 46 28 17 46 75 18
Amazon 23 26 11 23 16 10 23 41 10
Central Am. 20 15 35 11 28 13 11 18 12 11 46 13

Each column has the number of males and females included in the analysis for each group, then the difference (in kg or mm) between males and females for the variable mentioned, and
then, taking the female mean as 100%, the difference with the male in percentage is reported. See text for comments.


Table 11. Mean mass of vertebrate prey (MWVP, kg) for jaguar in forest and flood
plain areas. = with domestic stock, ** = without domestic stock.

Forest ** Mexico Belize Peru Forest Areas
Feces Feces Feces Average


18 5.6 302 5.4 25 10.7 345 5.8

Floodplain Brazil Brazil Venezuela Floodplain
Kills Kills/StO StO Average


59 113 80 70 18 50 145 89

Floodplain** MWVP MWVP MWVP
34.3 30.5 32.4

S= Stomach Contents
See text for comments

prey was capybara (Hydrochaeris hydrochaeris) and two peccary species.
When cattle and sheep were included, the MWVP value for this study
increased to 113.2 kg. The second Brazilian study was compiled from
Schaller and Vasconcelos (1978), and Almeida (unpubl. data), using stomach
contents and kills from the same region as the previous study. MWVP for
natural prey was 30.5 kg, and when natural and introduced prey were
included, the MWVP increased to 70 kg. Capybara, peccaries, feral hog (Sus
scrofa), and caiman comprised 85 percent of the non-domestic prey taken.
The average MWVP, including cattle, for the two Brazilian studies is 88.7
kg, a 15-fold increase compared with the preybase previously mentioned for
the forest jaguars. A sample of six stomach contents from the Llanos of
Venezuela gave an estimated MWVP of 98 kg, including domestic stock
(Mondolfi and Hoogesteijn 1986). A larger sample (18 stomach contents)


from the same area gave an MWVP value of 50 kg, where cattle remains
occurred in 56 percent of the sample (Hoogesteijn and Mondolfi 1993a, b).


Means for body mass, skull length, skull width, and skull index reported
in this study were higher than those previously obtained with a smaller
sample (Hoogesteijn and Mondolfi 1993b), and are in the general range
reported by other authors (Leopold 1959; Guggisberg 1975; Seymour 1989;
Oliveira 1992). The mean values for Pantanal jaguars are in the same range
as those reported before by Almeida (1976, unpubl. data). The means
reported here also are in the same range as those given by Seymour (1989)
for condylobasal length, zygomatic breadth, interorbital breadth, and length
of upper carnassial in a sample of 112 skulls of males and females
representing all subspecies.
The mean skull length of 243.6 7.9 and 215.2 12.3 mm and the
mean skull width of 166.4 6.4 and 148.7 8 mm (both for males and
females respectively) for Central American jaguars was fairly uniform
compared to the same measurements reported by other authors for jaguars
from the same area (males and females): 234.7 5.79 and 213.8 3.76 mm
for skull length, and 161.2 5.08 and 146.5 3.26 for skull width for the
Yucatan jaguar of Mexico (P. onca goldmani) (Aranda 1992). This Central
American subspecies is reportedly the smallest of all (Aranda 1992).
Rabinowitz and Nottingham (1986) reported that skull length and width of
jaguars in Belize (without stating subspecies, probably P. onca goldmani)
measured for males and females (mean S.D. in mm) were respectively:
length, 232 26 (n=16 males), 216 13 (n=3 females); width, 163 8
(n=16 males), 150 11 (n=5 females).
Important size variations in the jaguar have occurred since its arrival in
America. Paleontological data suggest that jaguar "ancestors" were already
present in the late Pliocene of North America, approximately 2-3 MYBP
(million years before present). They also may have been part of the Holartic
distribution of a large Panthera species. A jaguar related felid, Panthera
paleoonca, was already present in Texas in the late Pliocene. It differed from
the living jaguar in having longer carnassials (absolutely and relatively) and
in having longer and more slender superior canines (Meade 1945). In the
same area there is also evidence of a large felid (Felis studeri) that is related
to the living puma. This latter species and the previously mentioned Panthera


were nearly contemporaneous residents of the Texas Panhandle in the late
Pliocene (Savage 1960).
In the Pleistocene's early Irvingtonian (1.5-1.9 MYBP), jaguars were
abundant, while pumas were not, and where jaguar numbers and distribution
shrank over time, puma numbers increased. During the Late Pleistocene (Late
Blancan, ca 2 MYBP) pumas were only known from localities in southern
North America. Pre-Wisconsinan jaguars (ca. 0.25 MYBP), on the other
hand, ranged as far north as Washington, Nebraska, and Maryland. During
the Wisconsinan, or last North American glaciation (less than 0.2 MYBP),
the jaguar finds do not range as far north, reaching Nevada, Missouri, and
Tennessee, and during the Late Pleistocene (less than 0.25 MYBP) the
opposite occurred, pumas were found as far north as Idaho and Wyoming.
More recently, jaguar records are concentrated in the southern parts of North
America (Florida, Texas, and Tennessee), so the evidence indicates a gradual
restriction of the jaguar's range in the Pleistocene-Holocene, although this
general trend was probably influenced by a sequence of minor glacial-
interglacial shifts. This reduction of the jaguar's range was followed by a
reduction in body size. The Wisconsinan (ca 0.125 MYBP) jaguar (P. onca
augusta) was 15-20% larger than its living counterpart. There is a
progressive size reduction throughout this sequence in the Neartic, and this
tendency is more pronounced in more recent times in the Holocene (less than
10,000 years ago), with specimens of intermediate size between Wisconsinan
and living jaguars. Also there is a gradual shortening of the limbs, specially
the metapodials, leading from a more generalized type to the characteristic
jaguar form adapted to life in the forests, streams, and broken country
(Kurten and Anderson 1980). Kurten (1965) stated that the large Pleistocene
form probably was in direct genetic continuity with recent jaguars in areas
where they still survive. Analyzing the size trends of the Pleistocene felids in
Florida, he suggested that two important factors in short term oscillations are
noted: (1) changes in the animal's adaptation to compensate for impoverished
environment by size reduction (size could increase again under conditions of
a favorable prey base); and (2) the adjustment to climatic and environmental
changes. This latter factor gains probability when other data suggest an
actual decrease in numbers, as in the case of the fossil jaguars of Florida
(Kurten 1965; Kurten and Anderson 1980).
In South America, Panthera is definitely known from the Ensenadan
onward (ca 0.4 to 1.5 MYBP) and Lujanian (ca 0.4 to 0.01 MYBP) in the
late Pleistocene (Simpson 1970; Kurten 1973; Kurten and Anderson 1980;
Anderson 1984; Seymour 1989). The jaguar and puma were already present


in South America during the phases of contraction and expansion of
savanna/forests areas in the Amazon region. Due to recurrent glaciations,
growth of polar ice caps, sea currents, sea level regression, decreased rainfall,
and increased fire frequency, the savanna/woodland expansion heightened
approximately 18,000 YBP. Forested areas were reduced to island-like
refugia and/or gallery forests along rivers and lagoons in areas where climate
remained sufficiently humid to support forest biota. During that time, both
felids and a large saber-toothed felid coexisted with an extremely large-sized
assemblage of grazer and browser edentates and ungulates (e.g. megatheres,
toxodons, glyptodonts, and haplomastodonts). This megaherbivore complex
went extinct only some 8,000-10,000 YBP. With the new expansion of
forested areas deriving from climatic shifts and a more humid climate, only
the grazer/browser species more adaptable to savanna and forest conditions
like Tapirus, Hydrochoerus, Tayassu, and Dasypus prevailed (Rancy 1991).
Today, the largest jaguars persist in the Pantanal of Mato Grosso (P.
onca paraguensis) and the Llanos of Venezuela (P. onca onca), both
floodplain areas (the Llanos nearer to the Equator) that are widely separated
but possess some similar ecological features. Both are flooded 5-6 months of
the year, covered in part with extensive gallery and semideciduous forests and
have to a certain extent a similar preybase (Schaller and Crawshaw 1980;
Crawshaw and Quigley 1991; Hoogesteijn and Mondolfi 1993a). Some
questions arise regarding the size reduction that this felid underwent from the
Pleistocene to the present and the actual large sizes of individuals from the
two floodplain populations. These larger jaguars could represent descendants
that maintained their larger size due to the better feeding conditions in the
floodplain. On the other hand, local populations could have become bigger
from the year 1,600 A.D. onwards, with the introduction of plentiful and
vulnerable prey such as feral cattle, calves and horse foals. These prey
constitute a sizable part of their diet; cattle constituted 38, 48 and 56% of
stomach contents or kills in three studies, two in the Pantanal and one in the
Llanos (Hoogesteijn and Mondolfi 1993b). These changes in size show the
great adaptability of this efficient predator of the neotropical forest
vertebrates. Most current studies relate jaguars to forested areas, but at the
beginning of this century, with less human encroachment, jaguars still lived in
open areas, like the Argentinean Pampas, where they sought cover in the high
grass patches near lagoons and streams, areas practically devoid of forests
(Canevari 1983). Also, jaguars lived in the lower Llanos areas where only
small strips of gallery forests at the edge of rivers and temporary streams
existed between enormous savanna expanses (Hoogesteijn and Mondolfi


1993b). In both places, due to the lack of extensive cover, they were easily
It is possible that the jaguar as most of the other neotropical spotted
cats, exhibits a certain intolerance to colder climates and their range waxed
and waned with the recurrent glaciations. In the procyonids, Mugaas et al.
(1993) have demonstrated that the raccoon (Procyon lotor) has the highest
basal metabolic rate (associated with cold hardiness in mammals that live in
cold-temperate and Arctic climates), the highest diversity of diet (associated
with the ability to utilize a variety of food resources and to occupy a large
number of different environments), and also a high intrinsic rate of natural
increase. Other species of procyonids (e.g. Bassariscus, Pottos) showed
intermediate or lower adaptation capacities, reflected in their more restricted
distribution. The unique metabolic adaptations have given the raccoon the
physiological flexibility to generalize its use of habitats and climates, and
expand its geographic distribution to a greater extent than the other
procyonids. The tendency in the felids is probably similar for the puma,
adapted to both tropical and colder climates, and also with a high diet
diversity along its extensive distribution (Iriarte et al. 1990).
The analyzed data show that floodplain jaguars (Pantanal and Llanos)
have a larger body mass than the forest groups (Amazon and Central
America), with no significant differences in the body mass of the males from
the two floodplain groups. The same can be said for the statistically
significant skull measurements (skull length, width, and index and
condylobasal length in males and females; carassial length in males), which
also repeat the same tendency. The only exception was interorbital breadth, in
which the Central American population had the second largest mean in males
and the largest mean in the females. In the females, for the significant
measurements, the order of magnitude is almost the same as in the males, but
the Llanos female means for skull measurements were not significantly
different than those from the Amazon in some of the variables studied. The
group that is significantly smaller in all variables studied in both sexes (with
the exception of the interorbital breadth) is the Central American, and the
difference in mass within the group with the largest means is amazingly high.
Llanos males have a mean body mass 50 kg heavier than Central American
males (a difference of 86%). The females of the Pantanal weigh 35 kg more
than the Central American females (85% difference). Crawshaw and Quigley
(1991), also found that male jaguars in the Pantanal were approximately 80
percent heavier than males in Belize. This clearly relates to the prey base
available for the floodplain and the forest populations, with the Central


American jaguars having the smallest prey base (MWVP 5.5 kg), the
floodplain jaguars from the Llanos and the Pantanal the heaviest preybase
(MWVP 89 kg), and the Amazon forest jaguars occupying an intermediate
position (MWVP 11 kg). For the subtropical forest of Iguazu in southern
Brazil, Crawshaw (1995) estimated a MWVP of 14.4 kg, a result also
intermediate to the studies previously mentioned. The availability and
vulnerability of prey are probably higher in the floodplain than in forested
areas, important factors that influence prey selection by large felids (Sunquist
and Sunquist 1989).
There appeared to be a high and positive relationship between MWVP
values and body mass and skull measurements in the four populations
studied. They were all higher in the floodplain sites and lower in the forest
locations. Oliveira (1992), found a positive correlation between mean jaguar
body mass and MWVP (r=0.86). Also, this author states that there is a strong
correlation between body size and the usual mass of prey (MWVP), for a
wide range of carnivore species. For the puma, MWVP values also were
positively correlated (r=0.83) with body mass in all the different latitudes of
America (Iriarte et al. 1990). McNab (1972) and Kiltie (1984) postulated
that a correlation of body size with latitude in carnivores simply reflects the
size of the available prey. The results from this study on jaguar body mass,
skull measurements, and MWVP values, analyzed for forest and floodplain
populations, clearly agree with McNab (1972) and Kiltie's (1984)
conclusions. The results disagree with Rosenzweig's (1966) suggestions that
it was "unlikely" that the size of the available prey was a factor responsible
for variation in predator size. Iriarte et al. (1990) also state that puma prey
selection, as well as body size, would be strongly influenced by size of
available prey.
Data summarized by Oliveira (1992) from other authors show that in the
Brazilian Pantanal, jaguar and puma have a degree of spatial separation and
mutual avoidance, and although cattle is the main food for both species in the
area, jaguars mainly prey on adults and pumas almost exclusively on calves.
Also, the jaguar in tropical America has a higher MWVP (mean 49 kg) than
the puma (mean 18 kg). In the Peruvian Amazon, these two species and
ocelots preyed on different size classes: ocelots < 1 kg, puma 1-10 kg, jaguar
> 10 kg (Emmons 1987). These findings and the fact that jaguars eventually
kill pumas (Crawshaw and Quigley 1984) further support niche
differentiation between these large felids. Body size is constrained by the
presence of larger competitors (McNab 1972), and where these competitors
are absent, a greater mean body size may evolve in response to various


selective pressures. This argument is specially relevant to carnivore
communities, because competing species generally fall along a gradient of
body sizes (Rosenzweig 1966). For example, Nagorsen (1994) found that the
greater body size of insular Martes americana in the Pacific Northwest is
congruent with a lack of competitors on these islands, but the degree of size
divergence is determined by prey size or abundance. Both jaguar and puma
have smaller sizes and masses in areas of tropical forests, but the puma is
generally smaller in areas where it is sympatric with the jaguar and increases
in head-body size in areas outside of jaguar distribution, where it relies
heavily on larger prey items than in tropical areas (Iriarte et al. 1990).
The jaguar is an opportunistic hunter that utilizes a great spectrum of
prey species, more than 85 having been reported by Seymour (1989).
Emmons (1987) suggested that its massive head structure is an adaptation to
"cracking open" well-protected reptilian prey such as caimans, freshwater
turtles, and tortoises, and documented predation on some chelonian species
such as Geochelone carbonaria and G. denticulata (despite the shell's
thickness and toughness), Podocnemys unifilis and Platemys platycephala
(Emmons 1989). Other odd prey species mentioned by other researchers
include the Orinoco dolphin (Inia geoffrensis) and saltwater chelonians
(Chelonia mydas, Lepidochelys olivacea). The jaguar can subdue species
potentially more dangerous or larger in size, such as crocodilians, giant-
anteater (Myrmecophaga tridactyla), white-lipped peccary (Tayassu pecari),
and tapir (Tapirus terrestris), species which the puma usually does not prey
(Crawshaw and Quigley 1984; Hoogesteijn and Mondolfi 1993b; Carrillo et
al. 1994). Further studies are needed to determine the ecological factors
influencing jaguar and puma prey selection in areas of known prey
The differences between the jaguar samples relate not only to body
mass, skull sizes, or MWVP; there are also great differences in home range
sizes. These differences are influenced by the type of habitat, the prey
density, and the occurrence and degree of wet season flooding (Schaller and
Crawshaw 1980; Rabinowitz and Nottingham 1986; Crawshaw and Quigley
1991; Crawshaw 1995).
A revision ofPanthera onca is needed with regard to the validity of the
present subspecies listing. A complete craniometric statistical study and DNA
typing are needed. The results of this study highlight that the Llanos
population is significantly different in body size and most of the skull
measurements analyzed, compared to the Amazon jaguar, despite the fact that
both are included in the same subspecies. The results also show little


variation in the Central American group, suggesting that the five subspecies
may in fact be a single subspecies.
Nelson and Goldman (1933) proposed a total of 16 jaguar subspecies,
many based on one skin or one skull, or on skull characters used to describe
subspecies that often varied within the same population. Pocock (1939)
reduced the number of subspecies to eight, and he would have reduced them
more if he had had complete access to the skull measurements used but not
published by Nelson and Goldman (1933), who only gave measurements for
some of the type skulls. Cabrera (1957) accepted Pocock's proposition to
reduce the number of subspecies to three valid and one dubious one. Seymour
(1989) suggested that, although Pocock did not have access to sufficient
specimens in order to critically evaluate all the subspecies, his information
implies that P. onca goldmani could be made into a synonym for P. onca
centralis; P. onca centralis, arizonensis, and veraecrucis could be
synonymous with P. onca hernandesii, and P. onca peruviana could be
synonymous with P. onca onca. If these changes were made, there would
remain only three subspecies P. onca hernandesii, P. o. onca, and P. o.
paraguensis. For this last subspecies, Cabrera (1957) used the synonym
palustris, which is based on a fossil, prompting Seymour (1989) to suggest
that this synonym, following Nelson and Goldman (1933), should not be used
in an extant subspecies. The reduction in the subspecies number is not only
important from a taxonomic point of view but also from an ecological and
conservationist one. The increase of our understanding of the phyllogenetical
heritage, and morphological and ecological variation within the species is a
priority for conservation.


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