1 HOME RANGE SIZE, HABITAT ASSOCIATI ONS AND REFUGE USE OF THE FLORIDA PINE SNAKE, Pituophis melanoleucus mugitus IN SOUTHWEST GEORGIA, U.S.A. By GABRIEL J. MILLER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008
2 2008 Gabriel J. Miller
3 To my son, for a future where he can di scover and appreciate the natural world.
4 ACKNOWLEDGMENTS This research was performed under Georgia De partment of Natural Resources scientific collecting permits (2007 permit #29-WC H-07-149; 2006 permit #29-WTN-06-109; and 2005 permit #29-WTN-05-166) and the University of Florida Institutional Animal Care and Use Committee permit # E741. Funding was provided by the Florida Fish and Wildlife Conservation CommissionÂ’s State Wildlife Grants program (Grant # SWG 05-020, Agreement #060010); the University of Florida, and the Joseph W. Jones Ecological Resear ch Center. I acknowledge the Jones Center for allowing me to conduct my re search at Ichauway a nd for providing equipment needs and field assistance. I thank my graduate committee: Lora L. Smith, Steve A. Johnson and Dick Franz for providing advice, insight and ment orship. I thank Lora Smith, David Steen, Sean Sterrett, Aubrey Heupel, Jen Linehan, Kelly McKean, Chris Thawley, Matt Greene, and Phil Shirk for assistance with radio-tracking and Jean Brock for her invaluable assistance with GIS applications. Mike Connor, Shannon Hoss, Davi d Steen and Scott Wiggers are acknowledged for their statistical advice and guidance. Last ly, I thank my wife Melissa and son Brayson for their support and encouragement desp ite the long hours and difficulties.
5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES................................................................................................................ .........8 ABSTRACT....................................................................................................................... ..............9 CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW..............................................................11 Literature Review.............................................................................................................. .....11 Study Objectives............................................................................................................... ......14 2 HOME RANGE SIZE OF FLORIDA PINE SNAKES, Pituophis melanoleucus mugitus IN SOUTHWEST GEORGIA.................................................................................15 Introduction................................................................................................................... ..........15 Methods........................................................................................................................ ..........19 Study Site..................................................................................................................... ....19 Data Collection................................................................................................................ 20 Home Range Size............................................................................................................21 Data Analyses.................................................................................................................. 22 Results........................................................................................................................ .............22 Home Range Size............................................................................................................22 Seasonal Patterns in Home Range Size...........................................................................23 Discussion..................................................................................................................... ..........24 3 HABITAT ASSOCIATIONS AND REFUGE USE IN FLORIDA PINE SNAKES, Pituophis melanoleucus mugitus IN SOUTWEST GEORGIA.............................................38 Introduction................................................................................................................... ..........38 Methods........................................................................................................................ ..........41 Study Site..................................................................................................................... ....41 Data Collection................................................................................................................ 42 Habitat Associations........................................................................................................43 Microhabitat Use and Activity Patterns..........................................................................45 Refuge Use..................................................................................................................... .45 Results........................................................................................................................ .............46 Habitat Associations and Microhabitat Use....................................................................46 Activity Patterns.............................................................................................................. 47 Refuge Use..................................................................................................................... .48 Discussion..................................................................................................................... ..........49
6 4 CONCLUSIONS AND MANAGEMENT IMPLICATIONS................................................60 LIST OF REFERENCES............................................................................................................. ..65 BIOGRAPHICAL SKETCH.........................................................................................................72
7 LIST OF TABLES Table page 2-1 Home range data for radio-tracked Florida pine snakes ( Pituophis melanoleucus mugitus ) using minimum convex polygons (MCP), local convex hulls (LoCoH), and kernel density estimates (KDE) at Ichauway, Baker County, Georgia..............................29 2-2 Seasonal minimum convex polygon (MCP) home range size of Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.........................30 3-1 Ranking matrix of Florida pine snake ( Pituophis melanoleucus mugitus ) habitat use at the landscape scale on Ic hauway, Baker County, Georgia............................................53
8 LIST OF FIGURES Figure page 2-1 Map of Ichauway showing land c over classes, Baker County, Georgia............................31 2-2 Minimum convex polygon (MCP) home ra nge diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Baker County, Georgia.........32 2-3 Kernel density (KDE) home range diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Ba ker County, Georgia...........................33 2-4 Local convex hull (LoCoH) home range diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Ba ker County, Georgia...........................34 2-5 Relationship between body size (snout-t o-vent length; SVL) and annual minimum convex polygon (MCP) home range size fo r 12 adult Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia...........................................35 2-6 Mean minimum convex polygon (MCP) home range size by season for 12 (8 males and 4 females) adult Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.....................................................................................36 2-7 A comparison of seasonal minimum c onvex polygon (MCP) home range size of male (n = 8) and female (n = 4) Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia..................................................................37 3-1 Landscape scale habitat selec tion for a Florida pine snake ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia..................................................................54 3-2 Landscape study sites selected for la ndscape random point generation based on locations of Florida pine snakes ( Pituophis melanoleucus mugitus ) on the Ichauway property, Baker County, Georgia.......................................................................................55 3-3 Mean distance ratios (1 SE) for landscap e and within home range scale habitat use across eight distinct habitat t ypes for Florida pine snake ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia..................................................................56 3-4 Microhabitat use by 12 radio-inst rumented Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia...........................................57 3-5 Activity patterns of Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.....................................................................................58 3-6 Refuge use by 12 radio-instrumented Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia..................................................................59
9 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science HOME RANGE SIZE, HABITAT ASSOCIATIONS AND REFUGE USE OF THE FLORIDA PINE SNAKE, Pituophis melanoleucus mugitus IN SOUTHWEST GEORGIA, U.S.A. By Gabriel J. Miller December 2008 Chair: Steve A. Johnson Cochair: Lora L. Smith Major: Wildlife Ecology and Conservation Knowledge of spatial ecology, habitat, a nd resource requirements is useful when considering the conservation of a species. Very little is known regardi ng these aspects of the ecology of the Florida pine snake ( Pituophis melanoleucus mugitus ). In this study, 12 Florida pine snakes were radio-tracked within a managed tract of longleaf pine ( Pinus palustris ) forest in southwest Georgia. Home range estimates were generated using three distinct methods, and variations in home range si ze between sexes and across seas ons were examined. Habitat associations were examined at the landscape and within home range scales using Euclidean distance analyses. Microhabitat structure, ref uge use and association were also examined. Overall, minimum convex polygon (MCP) home ra nges of Florida pine snakes varied among individuals and were significantl y smaller in fall/winter than spring and summer. Specifically, males had larger home ranges in spring than in summer or fall/winter, whereas females did not differ across seasons. Florida pine snakes we re significantly associated with mixed pinehardwood forests at the landscape scale and all ot her habitats were used relative to their availability. I did not detect si gnificant habitat associations fo r pine snakes at the home range scale and snakes were not associated with any particular microhabitats. Pine snakes
10 predominately used pocket gopher burrows as fo ssorial refuges, though I did not detect an association with any refuges dur ing their above-ground activities. Florida pine snakes used large areas and sele cted for mixed pine-hardwood forest. Snakes were highly fossorial; therefore refuges, particularly southe astern pocket gopher burrows, are important resources for Florida pi ne snakes. It appeared that fragmentation by major roads and intensive agriculture may impede pine snake move ments. Effective conservation of Florida pine snakes will require the protect ion, restoration and management of native habitats. Protecting native upland ecosystems and natural disturbance processes such as fire, will benefit pine snakes and, thereby, provide and maintain necessary resources.
11 CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW The Southeastern Coastal Plain was originally dominated by the longleaf pine ecosystem. Today, less than 3% of the origin al longleaf pine forest remains intact (Noss et al. 1995), making it one of the most endangered ha bitats in the U.S. (Noss and Pe ters 1995, Ricketts et al. 1999). The longleaf pine ecosystem supports a dive rse reptile fauna (Guyer and Bailey 1993). However, many longleaf pine associated reptiles, such as the gopher tortoise ( Gopherus polyphemus ), a keystone species (Eisenberg 1983), and eastern indigo snake ( Drymarchon couperi ) are declining (Auffenberg and Franz 198 2, Moler 1992). The Florida pine snake ( Pituophis melanoleucus mugitus ), another inhabitant of the l ongleaf ecosystem, is also believed to be declining. The decline of this species is likely a result of hab itat loss and fragmentation, though road mortality and extensiv e collection may also be cont ributing factors (Franz 1992). Despite concerns about population declines, very little is known about the ecology or the status of Florida pine snakes. In order to effectivel y conserve this species, knowledge of their basic ecology and habitat requ irements is needed. Literature Review Florida pine snakes occur throughout the Sout heastern Coastal Plain. Their distribution includes most of Florida, southern Georgia, the southern tip of S outh Carolina and extreme southern Alabama (Conant and Collins 1998). Fl orida pine snakes are generally found in a variety of upland habitats, includ ing sandhills, pine flatwoods, oak scrub, and dry oak forests, all of which have well-drained, sandy soils and mode rate to open canopies (Ernst and Ernst 2003, Franz 1992). They are also known to occur in old fields and agricultural borders (Franz 1992). Florida pine snakes are most active in spring and early fall (Franz 1992). They over-winter below ground and, depending on temperature, may be inactive during extreme summer
12 temperatures (Ernst and Ernst 2003) Pine snakes are diurnal but much of their time is spent underground in the burrows of th e southeastern pocket gopher ( Geomys pinetis ; Franz 1992, 2005), although other underground refuges are also used. Florida pine snakes are adept at digging (Franz 1991); they use their spade-like head and large rostra l scale to gain access into the tunnels of southeastern pocket gophers. This beha vior has also been desc ribed for bullsnakes at northern pocket gopher ( Geomys bursarius) burrows ( P. catenifer sayi ; Carpenter 1982, Hisaw and Gloyd 1926), Florida pine snakes forage both above a nd below ground and take a variety of prey including mice ( Peromyscus spp.), cotton rats ( Sigmodon hispidus ), young cottontail rabbits ( Sylvilagus floridanus ), and ground nesting birds and their eggs (see Ernst and Ernst 2003). They also prey upon pocket gophers (Ernst and Er nst 2003, Neill 1951), in addition to using their burrows for refuge (Franz 2005). When unde rground, the bullsnake will constrict prey by pinning them to the burrow walls with their coils (His aw and Gloyd 1926). Florida pine snakes probably also use this techni que to restrain pocket gophers. Knowledge regarding Florida pine snake reprod uction is limited. Ernst and Ernst (2003) reported that P. melanoleucus breed in April and May. In th e southernmost portion of their range, mating may also occur in winter (A shton and Ashton 1981). Franz (2005) observed Florida pines snakes mating on 31 May. Male black pine snakes ( P. m. lodingi ) actively seek females over large areas, probably using olfaction to locate them (Reichling 1982), and this is likely true for the Florida pine snake as well. Nesting typically occurs from June through August, when 4-8 large leathery eggs are laid in underground cavities or burrows (Franz 1992). Female northern pine snakes excavate an egg cham ber rather than using existing cavities (Burger
13 and Zappalorti 1991). In Florida, pine snake e ggs typically hatch in September or October and total body length of hatchlings av erages 595 mm (Franz 1992). Little is known about the spatial ecology of Florida pine snakes. To date, only one published study from north central Florida has do cumented home range size for the subspecies (Franz 2005; 57 ha average home range size). Large-bodied snakes, such as the pine snake presumably require large tracts of land to m eet their basic requiremen ts (Gerald et al. 2006a, 2006b; Dodd and Barichivich 2007, Hyslop 2007). For ex ample, prey may be sparse or patchily distributed (Gregory et al. 1987) requiring extensive movements. Also, overwintering sites of may be far removed from summer feeding areas, as has been show n for some crotalids (Reinert and Zappalorti 1988) with movements from winter den sites to foraging sites exceeding 7 km (unpublished data, reported in Brown 1993). Repr oductive activities, such as males actively searching for mates or females finding nest site s may determine a snakeÂ’s use of space as well (Gregory et al. 1987). Franz (2005) noted that Florid a pine snakes used pocket goph er burrows as refuges at a higher frequency than other species, but the degr ee to which pine snakes are dependent upon this species for food and shelter is unclear. Pocket gophers are considered ecological engineers (Miller et al. 2008, Reichman and Seabloom 2002) a nd their burrows provide refuge to a variety of species. Gopher burrows serve as the primar y habitat for some rare arthropods (see Skelley and Gordon 1995, Skelley and Woodruff 1991). They also provide refuge to many reptiles and amphibians (Funderburg and Lee 1968) including pine snakes. Recent evidence suggests that southeastern pocket gopher populati ons are declining (Georgia Department of Natural Resources 2008); the impact that these declines may ha ve on pine snakes remains unclear.
14 The results of this study will increase our knowledge of pine snake ecology as well as contribute to improved decision-making for land acquisition and habitat management for the benefit of pine snakes. This information will ulti mately assist managers in developing the most effective conservation practices for Florida pine snakes. Study Objectives To effectively implement conservation objectives for the Florida pine snake, a greater understanding of their basic ecology is needed. My objectives were to determine 1) spatial use, 2) habitat association, and 3) re fuge use of Florida pine snakes within a managed upland pine forest matrix in southwest Georgia. In Chap ter 2, I estimated annual home range size of adult Florida pine snakes. Differences in home range size between sexes and across seasons were also examined. In Chapter 3, I examined habitat a ssociation at both the la ndscape and within home range scale based on JohnsonÂ’s (1980) natural orders of selection; habitat association at the local scale was examined using habitat structure. Also in Chapter 3, I quantified fossorial refuge use and examined association with specific refuge types, including pocket gopher burrows. In Chapter 4 I summarized the major conclusions of th is study and the implications for Florida pine snake conservation.
15 CHAPTER 2 HOME RANGE SIZE OF FLORIDA PINE SNAKES, Pituophis melanoleucus mugitus IN SOUTHWEST GEORGIA Introduction The main threat to biodiversity is habitat loss, fragmentation and degradation (Wilcove et al. 1998). Gibbons et al. (2000) recen tly pointed out that reptiles, as a group have been largely ignored in conservation, yet they are also likely to be highly affected by habitat loss. The longleaf pine ( Pinus palustris ) ecosystem in southeastern Unit ed States harbors the highest reptile diversity in North America (Guyer and Ba iley 1993); several reptil e species such as the gopher tortoise ( Gopherus polyphemus ) which is a keystone speci es (Eisenberg 1983), and the eastern indigo snake ( Drymarchon couperi ), both of which are charact eristic of the longleaf pine ecosystem, are declining due to habitat loss (Auffenberg and Franz 1982, Moler 1992). The status of other longleaf pi ne associated species such as the Florida pine snake ( Pituophis melanoleucus mugitus ) is unknown. The Florida pine snake is a large, albeit secre tive, snake that is native to the Southeastern Coastal Plain region of North America (Franz 1 992). They have a continuous distribution that includes much of Florida (excl uding the Everglades) and southe rn Georgia, as well as the extreme southern regions of South Carolina and Alabama (Conant and Collins 1998). Florida pine snakes occur in a variety of upland habitats within the S outheastern Coastal Plain (Franz 1992), with the primary historic ha bitat type being the longleaf pine ecosystem. However, the once-dominant longleaf pine forest and associated habitats have be en significantly altered (Frost 1993) and it is estimated that >97% of the origin al longleaf pine ecosystem has been converted to agriculture, pine plantati ons, and urban areas (Noss et al. 1995). The few tracts of longleaf pine that remain are highly fragmented (Noss et al. 1995). It is unclear wh at this loss of upland
16 habitats means for Florida pine snakes and this uncertainty is co mpounded by our lack of knowledge regarding their natural history. Franz (1992) suggested that populations of Florid a pine snakes are decl ining due to habitat loss. Despite this concern, the Florida pine snak e is only afforded the lowest conservation status, by the International Union for th e Conservation of Nature, whic h lists the parent species, P. melanoleucus as a Red List category of Â“Least ConcernÂ” (Hammerson 2007). Legal protection is lacking; the federal government does not reco gnize pine snakes as protected. State protection status is also minimal with Alabama, Florida a nd South Carolina listing Florida pine snakes as least or special concern; wher eas Georgia does not provide prot ection. More information is needed on the status and ecology of the species to determine if it warrants increased legal protection or a higher conservation status. Aspects of the spatial ecology of the Florida pine snake, including home range size, are particularly important for conservation and manage ment of the species. Home range data can provide insight into habitat use, intraspecifi c interactions (e.g., re production, territoriality) (Gregory et al. 1987) and seasonal va riations in spatial use (Macartn ey et al. 1988). Differences in sex-specific spatial use can also be established. Home range is defined as the area an animal traverses for its normal daily activities (Burt 1943 ). The concept has been further refined to include temporal considerations (e.g., annual or seasonal home ranges; Gregory et al. 1987). Several methods have been devised for quan tifying home range size. They include, among others, minimum convex polygons (MCP) (H ayne 1949, Mohr 1947), kernels (Powell 2000, Seaman and Powell 1996, Worton 1989), and mo re recently, local convex hulls (i.e. k -nnch or LoCoH; Getz and Wilmers 2004, Getz et al. 2007). The latter two methods incorporate utilization distribution, which is the probability model of home range that considers the relative
17 amount of time an animal spends in a ny place (Seaman and Powell 1996). Utilization distribution methods can identify areas of habitat that are partic ularly important to an animal. The minimum convex polygon method (MCP) is one of the simplest and most commonly used methods for estimating home range size. An MCP is the smallest possible polygon drawn around all of an animalÂ’s locations (Hayne 1949). Although this method has historic relevance, it has several short-comings. Minimum convex polygons have no statistical basis (points and their relationship to each other within the pol ygon have no bearing on th e home range estimate), they can incorporate large areas not actually used by the animal, and there is an assumption of even use of the area within th e polygon (Powell 2000). Desp ite these limitations, the MCP method is useful in providing an estimate of th e overall extent of an animalÂ’s home range. The kernel density estimator (KDE) is one of the most widely used methods for determining home range size and utilizati on distribution (Powell 2000, Worton 1989). This method produces probability contours, or kern els, around individual points, based on the intensity of use, which collectively produces a th eoretical home range. Fixed KDE is considered the most accurate of the kernel methods (Seaman and Powell 1996). Size of individual kernels is based on a smoothing parameter ( h ). The optimum value of h is typically determined using objective statistical methods (P owell 2000, Worton 1995), such as l east-squares cross-validation ( lscv ; Seaman and Powell 1996; Worton 1989, 1995). However, lscv is sensitive to autocorrelation (i.e. overlapping points due to hi gh site fidelity), which can greatly Â“undersmoothÂ” kernel shape and thereby underest imate home range size (Seaman and Powell 1996, Silverman 1986, Worton 1989). Other methods for determining h such as bias cross-validation ( bcv ), are more liberal, but this method may Â“over-smoothÂ” kernals when locations are autocorrelated, thereby overestimating home range size (Worton 1995). Row and Blouin-
18 Demers (2006) suggested using an h value that yields a home range estimate similar to that of MCP for species with high site fidelity, such as many reptiles. However, a more objective method for selecting h such as using the mean of lscv and bcv may be more appropriate (Blouin-Demers 2006). Local convex hull (LoCoH) is a relatively new method for estimating home range size and utilization distribution (Getz and Wilmers 2004). It is most useful in areas with diverse topography or in fragmented habitat (i.e. lands capes with hard boundaries) (Getz et al. 2007). Like KDE, LoCoH is a non-parametric, objective me thod that produces kernels, in the form of isopleths, around animal locations (Getz and Wi lmers 2004, Getz et al. 2007). LoCoH home ranges are created based on a chosen value k (the number of nearest neighboring locations), and its value is unique for each home range estimation. Selection of the k value is accomplished by running the model with a series of increasing k -values and examining th e resulting home range size estimates. The optimal k is the value obtained when home range size reaches an asymptote in relation to k Isopleths are generated around the points based on k and the resultant adjoining of isopleths determines the home range size estimat e and delineation of core areas. However, the LoCoH method can over-estimate home range size when there are outlyin g points (as can occur with MCPs), and LoCoH can also exclude areas ad jacent to portions of the home range with high concentrations of locations (are as that would seem likely to be used by the animal); these exclusions are attributed to the geometry and autocorrelation of th e locations (A. Lyons, University of California, Berkley, CA, pers. comm. ). Despite these issues, LoCoH can provide a more conservative estimate of home range size than MCP, in that it excludes large areas not used by the animal, and it recognizes hard boundaries. Additionally, LoCoH provides the benefit of
19 identifying areas of intense use (i.e. core areas), which could include high quality habitat or key resources within the habitat. In this study, I addressed a need for add itional information on the spatial ecology of Florida pine snakes. I estimate d home range size of Florida pine snakes in southwest Georgia, using the three methods outlined above. My goal was to provide home range size estimates that could be compared to other published studies for this species and other large terrestrial snakes (Reinert 1992, Rodrguez-Robles 2003, Hyslop 2007, Wund et al. 2007), as well as to provide the first estimates of core area size in Florida pine snakes. Using MCP estimates, I tested for seasonal variation in home range size as well as differences in home range size between males and females. An improved understanding of pi ne snake spatial ecol ogy will provide resource managers with additional knowledge that will aid in the conservation and management of this species and its habitat. Methods Study Site This study was conducted at the Joseph W. Jone s Ecological Research Center at Ichauway in Baker County in southwest Georgia (Figure 2-1) Ichauway is a privately owned tract of land that is managed for maintenance of the longlea f pine ecosystem and traditional quail (northern bobwhite; Colinus virginianus ) hunting. Approximately 60% of the 11,740 ha property is firemaintained second-growth longleaf pine forest (approximately 80 yrs ol d) with native ground cover including wiregrass ( Aristida stricta ) and native legumes (Goebel et al. 2001). Other pines (e.g., slash pine, P. elliottii loblolly, P. taeda and short-leaf pine, P. echinata ) and hardwoods (typically oaks, Quercus spp.) are also present within the landscape. Additi onal upland habitat types include longleaf pine restor ation plots, slash pine and l oblolly pine plantations, small agricultural fields (inclu ding wildlife food plots), old field ar eas and small urban centers. There
20 are numerous small isolated wetlands ranging from dense cypress ( Taxodium spp.) /gum ( Nyssa sylvatica ) swamps to open, grassy marshes with varyi ng hydroperiods. The Flint River forms the southeastern border of Ichauway and Ichawa ynochaway Creek bisects the property and flows into the Flint River at the sout hern edge of the property. Nume rous dirt roads exist on site; Ichauway is also bisected by two paved highways and several small, paved rural county roads. Adjacent land uses include center-pivot irriga tion agriculture, a hunting preserve and a small plantation. Management objectives at Ichauway include longleaf pine restoration, quail and whitetailed deer ( Odocoileus virginianus ) management, and conserva tion of the endangered redcockaded woodpecker ( Picoides borealis ). Prescribed fire is used extensively to facilitate management goals. Hardwoods have been rem oved on approximately 2000 ha of the property to allow reintroduction of fire and to restore longleaf pine and native ground cover. Data Collection Twelve Florida pine snakes (8 male and 4 fema le) were captured either by hand or in snake trap arrays (Rudolph et al. 1999, Burgdorf et al. 2005) from September 2006 through May 2007. The following measurements were taken on all sn akes: snout-to-vent length (SVL), tail length (both measured to the nearest 1 mm), and mass (measured to the nearest 1 g); sex was determined by cloacal probing. Each snake was im planted with a passive integrated transponder (PIT) tag (Biomark, Inc., Boise, ID) for individua l identification. Snakes were implanted with radio transmitters (Model SI-2 a nd SI-2T, 9g; Holohil Systems, Ltd., Carp, Ontario, Canada), by wildlife veterinarians using the method devel oped by Reinert and Cundall (1982). Transmitter weight did not exceed 5% of the snakeÂ’s body ma ss. Three snakes were implanted in fall 2006 and the remaining nine were implanted in spring 2007. I released all snakes at the site of capture within 3-5 days after surgery. Transmitters were removed at the completion of the study.
21 I radio-tracked snakes using a R1000 radio te lemetry receiver (Com munication Specialists Inc., Orange, CA) with a 3-element folding Yagi antenna (Wildlife Materials International, Inc., Murphysboro, IL). Snakes were tracked for at least one calendar year between September 2006 and June 2008. During spring, summer, and fall (22 March to 20 November) I tracked snakes every 3-4 days, whereas in winter (21 November to 21 March) snak es were tracked once a week. I tracked snakes on an alternating schedule (mor nings and afternoons) to reduce time effects. Snakes were located via homing (Mech 1983) and UTM coordinates (NAD 1983, Zone 16N) of locations were collected using a GeoExplorer 3 global positioning system (GPS; Trimble Navigation, Ltd, Sunnyvale, CA), which was accu rate to within approximately 2 m. Home Range Size I used three methods to calculate home ra nge size: minimum convex polygon (MCP; Mohr 1947, Hayne 1949), kernel area (KDE; Powell 2000, Seaman and Powell1996, Worton 1989, Worton 1995) and fixed local conve x hull (LoCoH; Getz and Wilmer s 2004, Getz et al. 2007). I used 100% MCP to capture the entire area used by each snake, including all outlying points (Figure 2-2). To examine areas of concentrated use, I used 95% kernel density estimates (Figure 2-3) with 50% core areas (Samuel et al. 1985), as well as 100% and 50% isopleths for fixed local convex hulls (LoCoH). I used HawthÂ’s Tools extension (Beyer 2004) in ArcMap 9.1 (ESRI, Redlands, CA) to produce MCPs and KDEs. I calculated 100% and 50% isopleths for fixed local convex hulls (LoCoH) (Figur e 2-4) using the LoCoH extensi on (University of California, Berkley). To determine the optimum LoCoH estimates for each individual, I ran several iterations of the model for each indi vidual, using increasing values of k I then selected the k value where home range size reached an asymptot e (i.e. where home range no longer increased); the value of k was unique for each home range estimated.
22 Data Analyses I used linear regression analysis to determine if mean annual home range size varied with snake body size (SVL). Sex and seasonal compar isons were made using MCP data; seasons were defined as spring (21 March to 20 June), summer (21 June to 20 September) and fall/winter (21 September to 20 March). Fall and winter data were combined because of very low snake activity levels over this peri od. I compared MCP home range size by season and sex using a two-way analysis of variance (two-way ANOVA). A Tukey-Kramer test was used post-analysis to identify differences between sexes among seas ons. Data were natural-log transformed to ameliorate problems associated with non-normality and high variance. The significance level was set at = 0.05. Statistical analyses were performed using SAS ver. 9.1 and SAS Enterprise Guide 4.1 (SAS Institute, Inc., Cary, NC). On e male snake (PM-2B6F) was found dead (cause of death undetermined) at the start of the summ er season and was not in cluded in the summer data analysis. Results Home Range Size I tracked 12 Florida pine snakes for 209 to 581 days, with an average of 83 locations per snake (Table 2-1). MCP home ra nge size varied among individuals ( xTot = 59.2 29.3 ha; range = 18.6 Â– 156.8). Mean MCP home range size of male s did not differ significantly from that of females ( x Male = 70.1 40.5 ha, range = 25.7 Â– 156.8; xFemale = 37.5 29.3 ha, range = 18.6 Â– 80.7; t0.05, 9.91 = -1.30, P = 0.223; Table 2-2). Kernel density estimates (95% KDE) yielded the smallest home range size of the three methods used and showed the least varia tion among individuals and between sexes ( x Male = 27.1 4.3 ha, range = 20.0 Â– 36.1; xFemale = 27.0 1.0 ha range = 20.1 Â– 41.7; xTot = 27.0 4.1 ha;
23 range = 20.0 Â– 41.7). There were from one to six separate 50% KDE core areas within individual pine snake home ranges; 50% KDEs were similar in total size for males and females ( x Male = 4.0 0.7 ha, range= 2.7 Â– 5.4; xFemale = 4.6 2.1 ha, range = 3.1 Â– 7.7). Fixed LoCoH estimates (100% isopleths) were larger than 95% KDEs but were slightly smaller than MCP home ranges ( x Male = 61.2 34.2 ha, range = 21.5 Â– 135.9; xFemale = 29.3 15.9 ha, range = 18.7 Â– 52.4; xTot = 50.6 ha 24.5 ha; range = 19.0 Â– 135.9). LoCoH core areas (50% isopleths) ranged from one to three per snak e and were similar in size between the sexes ( x Male = 2.7 1.4 ha, range = 0.2 Â– 5.7; xFemale = 2.3 1.8 ha, range = 0.5 Â– 4.3; xTot = 2.6 1.1 ha; range = 0.20 Â–5.7). LoCoH estimates were similar to those derived with MCP, but excluded areas around the periphery of the home ra nges that were apparently not used by the snakes. Areas adjacent to high use sites within the home range were sometimes clipped out by the LoCoH model as a result of autocorrelation a nd geometry of the points (A. Lyons, University of California, Berkley, CA, pers. comm.), whic h may have underestimated home range size by removing areas that were likely used by the snake. Seasonal Patterns in Home Range Size There was no relationship between snake body size (SVL) and MCP home range size (R2 = 0.0673; Figure 2-5). However, two-way ANOVA re vealed that home range size varied by sex and season ( F0.05, 5, 27 = 7.16; P < 0.001). A Tukey-Kramer test confirmed that there was no significant difference between mean annual home range size of males and females ( F0.05, 1, 27 = 0.15; P = 0.6990), but home range size di ffered significantly among seasons ( F0.05, 2, 27 = 10.32; P = 0.005; Figure 2-6) and between males and females by season ( F0.05, 2, 27 = 3.34; P = 0.05; Figure 2-7). Seasonal home range size was significantly different in spring and fall/winter ( P <0.001) and summer and fall/winter ( P <0.05); however, spring and summer home range sizes
24 did not differ significantly ( P = 0.12). Although the Tukey-Kramer post-analysis found no significant difference in home range size between sexes within seasons (MSp vs. FSp, P = 0.44; MSu vs. FSu, P = 0.87; MF/W vs. FF/W, P = 0.70), nor between seasons for females (FSp vs. FSu, P = 1.00; FSp vs. FF/W, P = 0.74; and FSu vs. FF/W, P = 0.72), male home range size differed significantly between spring and summer (MSp vs. MSu, P = 0.02), and spring and fall/winter (MSp vs. MF/W, P <0.0001; Figure. 2-6). There wa s no difference between summer and fall/winter home range size in males (MSu vs. MF/W, P = 0.24). The only differences in home range size between sexes across seasons was betw een males in spring and females in fall/winter (MSp vs. FF/W P = 0.02; Figure 2-7). Discussion Each of the three home range estimators us ed in this study provided potentially useful information about pine snake spatial ecology. Th e MCP estimated the maximum area used by an individual within a year (annual home range size), whereas LoCoH and KDE provided information on core areas (e.g., superior habitat or key resources like food and refuge) within the overall home range. Use of the mean of lscv and bcv to derive a smoothing factor, h for KDEs yielded a home range size comparable to th e MCP as suggested by Row and Blouin-Demers (2006) Although small portions of the LoCoH isopleths were clipped out, in most cases the core areas identified with both utilization distribution methods overlapped. The issues of autocorrelation could have been reduced by subs ampling, however this may have led to loss of information (Desolla et al. 1999). I recomme nd using both MCP and either LoCoH or KDE to determine spatial requirements of pine snakes and other species that use discreet areas for prolonged periods of time (e.g., fo ssorial refugia, hibernacula). The overall MCP home range size of Florida pine snakes in this study was 59.2 ha, which is comparable to that obtained for the species in north-central Florid a (57.0 ha, MCP; Franz
25 2005). Although, the mean home range size of male s was similar in the two studies, female home range size was more than tw ice as large in my study as in the Florida study (37.5 ha as compared to 13.5 ha, respectively). The diffe rence in female home range size may be a reflection of the small sample sizes in both th is and the Florida study (n = 3; Franz 2005) coupled with high variability among individuals, but differences in resource availability may also have been a factor. Although MCP data were not presented, home range estimates (using 95% KDEs) for northern pine snakes ( P .m. melanoleucus ) were much larger than Florida pine snakes in this study (59.9 ha and 27. 0 ha, respectively; Gerald et al. 2006b). Moreover, in the northern pine snake study lscv was used to determine h which typically underestimates home range size, suggesting that if they used the same methods as were applied to my data, the reported home range size for northern pine snakes would have been even larger. This disparity may be related to differences in habitat quality between the two study sites. Whereas this study was conducted in relatively unimpacted habitat, the northern pi ne snake study was in an area highly fragmented by agriculture and other land uses. My estimates of Florida pine snake home range size were substa ntially larger than estimates for the western counterparts, P. c. catenifer (n=4, x Male = 2.29 ha; Rodrguez-Robles 2003) and P. c. deserticola ( x Male = 1.2 ha; x Female = 2.1 ha; Parker and Brown 1980). It is unclear why western Pituophis exhibit smaller home ranges than members of the eastern species. Perhaps these differences are due to contrast s in resource availability, competition, or environmental factors. More res earch investigating the factors dr iving differences in spatial use between western and eastern Pituophis is needed. I found no difference in mean annual home ra nge size between male and female Florida pine snakes. Home range size did, however, vary seasonally with spring and summer home
26 ranges being significantly larger than fall/winter ranges (Figure 2-6). The small fall/winter home ranges most likely reflected decreased activity due to decreasing temp erature and photoperiod; snakes were less frequently observed above ground and movements were concentrated around hibernacula such as pocket gopher burrows in fall/w inter (see Chapter 3). The large home ranges in spring and summer were likely related to m ovements associated with reproduction (Gregory et al. 1987). Pine snakes breed in spring (Ern st and Ernst 2003, Franz 2005), which, for males, may involve extensive movements outside the non-b reeding home range. Indeed, three males in this study moved more than 2 km straight line di stance in spring (G. Miller, pers. obs.), and I observed three mating events from early to mid-June, which coincided with the longest individual movements of males (G. Miller, pers. obs.). Female Florida pine snakes nest in summer (late June/July) (Lee 1967, Franz 1992, Franz 2005, Ernst and Ernst 2003). Although I did not observe nesting, in mid-July two female s (PM-3F3F and PM-3F1E) moved to locations outside of their initia l home ranges, and these movements may have been associated with nesting. Specifically, one of the females (PM-3F3F ) appeared gravid in mid-July and she moved approximately 250 m to an area outs ide her initial home range. She later returned to her initial home range and no longer appeared to be gravid. It is unclear what factors in addition to reproduction might influence home range size of Florida pine snakes. Snake body size was not co rrelated with home ra nge size in this study. However, I focused only on adult snakes (>910 mm SVL, Franz 1992) with little variation in body size. It may be that juvenile Florida pi ne snakes use smaller home ranges than adults, although further research is needed to determin e this. Intraspecific competition could also influence home range size in pine snakes. Home range overlap occurred on only a few occasions in this study, and only involved males and females during breeding season. In late winter/early
27 spring, however, a non-study male was found baski ng within 30 m of male PM-1879 (G. Miller, pers. obs.). A more detailed study is needed to determine whether pine snakes exhibit intraspecific competition. The home range size of Florida pine snakes in this study was similar to the one other study conducted for this subspecies (F ranz 2005). However, both studies had relatively small sample sizes. High variability in home range size among the snakes in each study suggests that larger sample sizes were warranted. Additionally, factor s that influence home range size need to be further studied, such as competition, intraspecific interactions, and resource availability. Both this study and that of Franz (2005) were conducte d within protected areas that are actively managed for maintenance of native fo rest types. These studies provide useful data in this setting, but additional studies are warranted to determin e the extent of variability in home range size among different populations of pine snakes and ac ross a range of habitats with varying degrees of disturbance. In particular, st udies are needed in areas that ar e more representative of existing landscape conditions (e.g., disturbed or fragmented habitats). Based on these data, we can begin to deve lop conservation management strategies addressing the spatial needs of Florida pine sn akes. Although the minimum viable population size for Florida pine snakes is not known, my es timates of MCP home range size can be used as a basis for determining the approximate spatia l requirements of a population. A population of 50 adults (a number that has been proposed as the minimum effective population size for most vertebrates; Franklin 1980) w ith non-overlapping home ranges would need nearly 3000 ha of habitat. This estimate should be interpreted with caution, because Florida pine snakes in different regions or different ha bitats might require mo re or less habitat than pine snakes at Ichauway. Ichauway is managed with frequent prescribed burns to maintain an open canopy
28 forest with diverse native ground cover, whic h may represent high quality habitat for pine snakes. Populations in disturbed or fragmented habitat may require significantly more habitat. In addition, Florida pine snakes may shift their home ranges within the landscape over time, thus requiring even more habitat. None theless, basic ecological studies such as this may be the first steps in developing an effective manageme nt strategy for Florida pine snakes.
29Table 2-1. Home range data for ra dio-tracked Florida pine snakes ( Pituophis melanoleucus mugitus ) using minimum convex polygons (MCP), local convex hulls (LoCoH), and kernel density estimates (KDE) at Ichauw ay, Baker County, Georgia. MCP Snake IDSex Location/ SnakeMonitoring Period SnoutVent length (mm) Mass (g) 100% (ha) 100% isopleth (ha) 50% isopleth (ha) 95% Contour (ha) 50% Contour (ha) PM-3060M795/14/07 5/16/081442.51147.0 25.7 21.5 3.224.4 4.8 PM-1879M835/14/07 6/17/081117.0 753.0 29.1 27.5 1.224.1 3.8 PM-2B6FM4910/18/06 5/14/071364.5 907.0 30.7 28.1 0.221.2 2.7 PM-4E45M696/12/07 5/26/081366.01156.0 38.1 39.5 2.420.0 3.5 PM-4F5DM806/12/08 6/20/081351.01048.0 30.6 28.1 0.725.0 3.1 PM-6571M1249/20/06 4/22/081376.01117.0 95.3 75.3 5.733.9 5.4 PM-025AM835/14/07 6/17/081367.5 843.0154.2135.9 3.436.1 5.1 PM-4666M835/14/07 -6/6/081371.51066.0156.8133.7 5.331.7 3.4 PM-3F3FF11710/18/06 4/29/081337.5 727.0 18.6 19.0 0.921.5 3.8 PM-3F1EF715/14/07 4/11/081332.51048.0 19.9 18.7 3.320.1 3.9 PM-5F5EF825/14/07 6/13/08 968.0 365.0 30.9 27.1 0.524.7 3.1 PM-612BF795/14/07 5/18/081319.01204.0 80.7 52.4 4.341.7 7.7 Male Mean---1344.51004.6 70.1 61.2 2.727.1 4.0 (SE) --(33.9) (53.5) (40.5) (34.2)(1.4) (4.3)(0.7) Female Mean---1239.3 836.0 37.5 29.3 2.327.0 4.6 (SE) --(90.5) (185.8) (29.3) (15.9)(1.8) (1.0)(2.1) Total Mean---1309.4 948.4 59.2 50.6 2.627.0 4.2 (SE) --(38.2) (70.2) (29.3) (24.5)(1.1) (4.1)(0.8) Kernel LoCoH
30 Table 2-2. Seasonal minimum convex polygon (MCP) home range size of Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. Snake IDSex # of Locations (Sp, Su, F/W)SpringSummerFall/Winter PM-3060M(27, 21, 31) 23.1 4.8 2.3 PM-1879M(30, 22, 31) 23.8 12.7 8.5 PM-4E45M(23, 18, 28) 35.6 5.7 5.1 PM-4F5DM(26, 23, 31) 30.2 18.0 0.2 PM-6571M(32, 23, 69) 84.9 11.3 3.9 PM-025AM(30, 23, 30)153.1 11.1 8.8 PM-4666M(29, 23, 31)153.6 7.3 1.7 PM-2B6FM(14, --, 35) 22.0 -2.7 PM-3F3FF(32, 22, 63) 9.5 7.6 5.8 PM-3F1EF(17, 23, 31) 9.4 15.9 3.5 PM-5F5EF(30, 24, 28) 26.8 12.8 2.7 PM-612BF(25, 25, 29) 37.6 65.034.4 Male Mean -65.8 10.1 4.2 (SE) -(20.4) (1.7) (1.1) Female Mean-20.8 25.311.6 (SE) -(6.9) (13.3) (7.6) Total Mean-50.8 15.7 6.6 (SE) -(14.9) (5.1) (2.6) 100% MCP (ha)
31 Figure 2-1. Map of Ichauway showing la nd cover classes, Baker County, Georgia.
32 Figure 2-2. Minimum convex pol ygon (MCP) home range diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Baker County, Georgia.
33 Figure 2-3. Kernel density (KDE) home ra nge diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Baker County, Georgia.
34 Figure 2-4. Local convex hull (LoCoH) home range diagram for Florida pine snake ( Pituophis melanoleucus mugitus ) PM-3060 at Ichauway, Baker County, Georgia.
35 y = 0.0997x 71.352 R2 = 0.0673 0 20 40 60 80 100 120 140 160 180 900100011001200130014001500SVL (mm)Area (ha) Male Female Figure 2-5. Relationship between body size (sno ut-to-vent length; SV L) and annual minimum convex polygon (MCP) home range size fo r 12 adult Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.
36 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 SpSuF/WNatural Log Area (ha) a a b Figure 2-6. Mean minimum convex polygon (MCP) home range size by season for 12 (8 males and 4 females) adult Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. Sp= sp ring (21 March Â– 20 June), Su= summer (21 June Â– 20 September) and F/W= fall and winter (21 September Â– 20 March). Common letters indica te non-significant s easonal differences.
37 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 SpSuF/WNatural Log Area (ha) Male Female a b a, b a, b b b Figure 2-7. A comparison of seasonal minimu m convex polygon (MCP) home range size of male (n = 8) and female (n = 4) Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. Sp= spring (March 21 Â– June 20), Su= summer (21 June Â– 20 September) and F/ W= fall and winter (21 September Â– 20 March). Common letters indicate non-significant seasonal differences.
38 CHAPTER 3 HABITAT ASSOCIATIONS AND REFUGE USE IN FLORIDA PINE SNAKES, Pituophis melanoleucus mugitus IN SOUTWEST GEORGIA Introduction Pine snakes ( Pituophis melanoleucus ) are large, fossorial snakes that occur in the eastern U.S., from southern New Jersey to Florida and as far west as southern Alabama (Conant and Collins 1998). Of the three recognized subspecies, all are associated with upland habitats with well-drained sandy soils. The Florida subspecies ( P. m. mugitus ) occurs throughout the Southeastern Coastal Plain (Franz 1992), the region that supports the highes t reptile diversity in North America (Guyer and Bailey 1993). There are c oncerns that, like other snake species in the region (Krysko and Smith 2005, Moler 1992, Tuberville et al. 2000), the Florida pine snake may be declining (Franz 1992). Several potential caus es of declines in snake populations have been suggested (Franz 1992), but habitat loss may be the most important. Unfortunately, little information is available regarding the habitat re quirements of Florida pi ne snakes; therefore, direct impacts of habitat loss on this species are not clearly understood. Historically, the Southeaste rn Coastal Plain was domina ted by the fire-maintained longleaf pine ecosystem (Frost 1993 ). Currently, < 3% of the or iginal longleaf pine habitat remains intact (Noss et al. 1995), and remaining l ongleaf pine forests are threatened due to the suppression of fire and subsequent hardwood en croachment (Frost 1993). Many forest lands have been converted to even-aged stands of off-site pines including slash pine and loblolly pine. Furthermore, remaining forest patches are highl y fragmented and isolat ed by other land uses (e.g., agriculture, commercial development and road s). The extent to which these impacts to the longleaf pine ecosystem have affected Florid a pine snakes has not been quantified, although Franz (1992) suggested that habitat loss was one of the main fact ors in recent population declines.
39 In north-central Florida, pine snakes were found to be asso ciated with hi gh pine/sandhill habitat as well as oak woodlands and oldfield si tes (Franz 1992, 2005). Ha bitat requirements of the closely related northern pine snake ( P. m. melanoleucus ) and Louisiana pine snake ( P. ruthveni ) are fairly well known (Burger and Za ppalorti 1986, 1988, 1989, 1991; Burger et. al 1988; Ealy et al. 2004; Zappalorti and Burger 1985; Duran 1998; Himes et al. 2006, Rudolph et al. 2007). Both species use upland pine/oak fore sts and are highly fossorial. Recent research on the Louisiana pine snake suggest s that they us e pocket gopher ( Geomys spp.) burrows as refuge (Rudolph et al. 2007) much like Franz (2005) found fo r Florida pine snakes. However, in New Jersey, the northern pine snake o ccurs outside of the range of poc ket gophers, and snakes in this region use other available refuges or excavate their own refugia (Burger et al. 1988). In southwest Georgia, Florida pine snakes occur w ithin the range of the southeastern pocket gopher ( G. pinetis ), but the degree to which pine snakes ar e associated with pocket gophers, and details about habitat selection, are unknown. Animals may select habitat differently de pending upon the scale examined (Johnson 1980, Moore and Gillingham 2006, Naugle et al. 1999). Johnson (1980) defined a hierarchical system of habitat selection that includes three different scales. First order se lection occurs at the broadest scale, within the geogr aphic range of a species; second or der selection determines home range of an individual or group (i.e. within a spec ific landscape); and third order selection is finer scale selection for specific habitats within an animalÂ’s home range. The terms preference, selection, use, and association often are used s ynonymously in habitat literature (Garshelis, 2000). Preference implies that an animal uses a pa rticular habitat irrespec tive of its availability or accessibility, which is difficult to measure. Therefore, in this study, the more general terms of habitat use, selection an d association are used.
40 Various methods have been developed to dete rmine habitat use. One of the most common methods is compositional analysis (Aebischer et al. 1993), whereby the proportion of different habitats available is compared to the proporti on of habitats used by the animal. Euclidean distance analysis (Conner and Plowman 2001, C onner et al. 2003), a more recent method, determines habitat use based on a comparison of the mean distance from animal locations to different habitats to that of random locations to th e same habitats. This method is less strict than compositional analysis and provides a greater array of information regarding habitat availability for each animal location (Conner et al. 2003). Florida pine snakes in north-central Florid a were highly fossorial and spent 81% of the time below ground, most frequently in southeas tern pocket gopher burro ws (Franz 2005). Pocket gophers ( Geomys spp.) have been referred to as eco logical engineers (Miller et al. 2008, Reichman and Seabloom 2002) and the burrows of southeastern pocke t gophers host several species of rare arthropods (e.g., Skelley and Gordon 1995, Skelley and W oodruff 1991). Pocket gopher burrows provide relatively stable environm ental conditions, as compared to the surface (Kennerly 1964) and offer suitable refuge for both invertebrates and vertebra tes. Several authors have suggested that there may be a strong a ssociation between Flor ida pine snakes and southeastern pocket gophers (Allen and Neill 1952, Franz 1992, 2005, Funderburg and Lee 1968). However, other than the detailed teleme try study by Franz (2005), the extent to which Florida pine snakes depend sp ecifically on pocket gopher burrows has not been investigated. Florida pine snakes also prey upon southeaste rn pocket gophers (Allen and Neill 1952), although again, the degree to which Florida pine snakes may depend on pocket gophers as a food resource is unknown. A recent report suggested southeaste rn pocket gophers were declining (Georgia Department of Natural Resources 2008), which ma y negatively affect pine snake populations.
41 Data are needed to determine the degree to which pine snakes are associated with longleaf pine forests versus other habitat types and the exte nt to which they use southeastern pocket gopher burrows versus other fossorial refuge sites. In this study I examined habita t associations and refuge use in the Florida pine snake on a tract of land with a wide array of upland habitats. I used radi o telemetry to track individual snakes for approximately one year. By closely m onitoring these individuals, I was also able to describe aspects of pine snake li fe history, i.e., seasonal activity pa tterns. The specific objectives of this study were to 1) determine if Florida pine snakes are associated with specific habitats at either a landscape or home range scale; 2) exam ine microhabitat use and activity patterns, and 3) describe and quantify use of fossori al refuges by Florida pine snakes. Methods Study Site I conducted this study at Ichauway, the resear ch site of the Jose ph W. Jones Ecological Research Center in southwest Georgia (See Chap ter 2, Figure 2-1). The 11,740 ha property is located in Baker County, approximately 16 km s outhwest of Newton, Georgia, USA. Ichauway, along with a few private quail (northern bobwhite, Colinus virginianus ) hunting plantations, harbors one of the few remaining contiguous tracts of native longl eaf pine forest in the region (Noss and Peters 1995). The major overstory component of uplands at Ichauway is secondgrowth longleaf pine (approxima tely 80 yrs old) with a rich diversity of native ground cover including wiregrass ( Aristida stricta ) and legumes. Other pines (e.g., slash pine, P. elliottii loblolly, P. taeda and short-leaf pine, P. echinata ) and hardwoods (typically oaks, Quercus spp.) are also present. Other land c overs include longleaf pine rest oration plots, pine plantations, small agricultural fields, wildlif e food plots, oldfield areas an d small urban centers. Upland management objectives include longleaf pine re storation and conservatio n, quail and white-tailed
42 deer ( Odocoileus virginianus ) management, and conservation of the endangered red-cockaded woodpecker ( Picoides borealis ). Management objectives are car ried out with prescribed fire (typically on a 2year rotation) a nd mechanical removal of hardwoods. Other habitats at Ichauway include numerous small isolated wetlands ranging from cypress ( Taxodium spp.) /gum ( Nyssa sylvatica ) swamps, to cypress savannas, to open, grassy marshes; two riparian systems, the Flint River and th e Ichawaynochaway Creek also are present on the property. Ichauway has numerous di rt roads that serve both as travel routes and fire breaks. The property is transected by two paved highways (Highway 200 and Highway 91) and several rural county roads. Ichauway is surrounded by inte nsive center-pivot irriga tion agricultu ral land, a small hunting preserve, and a small wildlife management area. Data Collection The 12 snakes used in this study were capture d either by hand or in snake trap arrays (Rudolph et al. 1999, Burgdorf et al 2005). Snakes were measured and weighed and sex was determined by cloacal probing. Measurements incl uded snout-vent-length (SVL) and tail length (TL). Snakes were surgically implanted with ra dio transmitters; three snakes were implanted in spring 2006 and nine additional snakes were implanted in spring 2007. Transmitters [model SI-2 (5) and SI-2T (7), Holohil Systems Ltd., Carp, ON, Canada] weighed 9g a nd did not exceed 5% of a snakeÂ’s body mass. Surger ies were performed by a wildlif e veterinarian using methods developed by Reinert and Cundall (1982). Snak es were chosen for implantation based on body size, thus they were not randomly distributed across the study site. After implantation, snakes were released at the site of capture and tracked using a R1000 telemetry receiver (Communication Specialists Inc., Orange, CA) with 3-element folding Yagi antenna (Wildlife Material s International Inc., Murphysboro, IL). Snakes were tracked every 3-4 days for one calendar year, except during winter (21 November to 21 March) when the tracking
43 interval was decreased to once every seven days due to minimal movements by snakes. Tracking time (morning or afternoon) was alternated daily to reduce time effects. Snake locations were acquired by homing (Mech 1983) and UTM coordi nates (NAD 1983, Zone 16N) of all locations were recorded with a GeoExpl orer 3 global positioning syst em (GPS; Trimble Navigation Limited, Sunnyvale, CA) which was accurate to within 2 m. Tracki ng was initiated in September 2006 and concluded in June 2008. A total of 999 unique sn ake locations were obtained, with an average of 83 locat ions per individual (range = 49-124). Habitat Associations Snake locations, as determined with the GPS, were imported into an existing land cover data layer that had been di gitized from 1992 color infrared orthophotography (1:12000 scale). Land cover (habitat) classes used in this anal ysis included agricultur e and wildlife food plots (AG); hardwood forest (HW); mixed pine-hardw oods (MX); natural pine forest (NP); pine regeneration plots and plantations (PP), scrub/sh rub or fallow land (SC), aquatic habitats (AQ), and urban areas (UR). Agricultural land was either wildlife food pl ots (<0.5 ha), small agricultural plots or large center-pivot agricult ural fields located ad jacent to Ichauway. Hardwood forests contained a mixture of species including southern red oak ( Quercus falcata ), live oak ( Q. virginiana ), laurel oak ( Q. laurifolia ), and water oak ( Q. nigra ). Mixed pinehardwood habitat had both pine and oaks in th e canopy. Natural pine habitat was predominantly mature longleaf pine with native ground cover, but also included area s of naturally occurring loblolly, shortleaf or slash pine Pine plantations were typical ly newly planted longleaf pine restoration plots, but also incl uded mature, even-aged stands of planted longleaf pine or slash pine with varying degrees of ground cover. Scru b/shrub included hardwood th ickets or old fields in varying degrees of succession. Urban areas in cluded developed sites (rural farms, barns or other buildings). Aquatic habita ts included all isolat ed wetlands and waterw ays. All habitats
44 (with the exception of agriculture urban and permanent aquatic ha bitats) are managed with fire on a 1-2 year rotation. Euclidean distance analysis (Conner and Plow man 2001) was used to determine whether Florida pine snakes exhibited habitat associa tions at either the la ndscape scale (JohnsonÂ’s 2nd order) or home range scale (JohnsonÂ’s 3rd order)(Johnson 1980). The analysis, as explained in detail in Conner and Plowman (2001) and Conner et al. (2003), is simply a pairwise comparison of the mean distances between animal locations and particular habitat types, and the mean distances between random loca tions and habitat types. For within home range analysis (JohnsonÂ’s 3rd order), the mean distance from snake locations (n = 999) was compared to 1000 random locations within each animalÂ’s MCP home range (see Chapter 2). To test for associ ations at the landscape scale (JohnsonÂ’s 2nd order), 12,000 random points within the individual hom e ranges were compared to those of 10,000 random locations within the Â“s tudy areaÂ” (Figure 3-1). The study area encompassed two disjunct areas, based on the locations of the radio-teleme tered snakes; the random locations were equally divided between the two areas. The first area was located north of Highway 200 and the other was just north of and to the south of Highway 91 (Figure 3-2). Random points were generated using HawthÂ’s tools. Distances to habitat cla sses were calculated usi ng the NEAR function in ArcMap 9.1 (ESRI, Redlands, CA). A multivariate analysis of variance (MANOVA) was used to determine if the snakes exhibited habitat associations at either the landscape (site wide ) or home range scale. If a significant effect was detected wi th MANOVA, pairwise t-tests were used to identify habitats with a significant association. Th e significance level was set at = 0.05 and statistical analyses were performed in SAS 9.1 (SAS Institute Inc., Cary, NC).
45 Microhabitat Use and Activity Patterns At each location, data on the snakeÂ’s pos ition (above or below ground) and activity (basking, moving, or feeding) were collected. Microhabitat data taken at each unique snake location included canopy cover, which was th e mean of four readings taken around a 1m2 quadrat centered over the snakeÂ’s location using a spherical dens itometer. Percent cover of shrubs, grasses, herbs, bare ground, and coarse woody debris also was estimated within the 1m2 quadrat centered over the snake, using the following cover class ca tegories: < 1%, 1-5%, 6-15%, 16-25%, 26-50%, 51-75%, 76-100%. The same data were collected at an equal number of randomly selected 1-m2 plots; each of these plots was placed at a random azimuth and distance (5-30 m) from the snakeÂ’s location. The averag e percent cover of each cover class for both snake locations and random locations were used in the analysis. A Chi-square test was used to determine whether snakes used microhab itats relative to their availability. Refuge Use I attempted to identify the refuge type at each location where a sn ake was below ground. Refuges included southeastern pocket gopher burrows (as determined by the presence of mounds), gopher tortoise burrows, mouse burrows ( Peromyscus spp.), nine-banded armadillo ( Dasypus novemcinctus ) burrows, and stump holes (which included stumps, burned out stump holes and tree tip-ups). Snakes we re considered to be using a partic ular refuge type if a structure (e.g., pocket gopher mound) was found within a 2 m ra dius of the snakeÂ’s location. If no refuge structure was visible within 2 m of the snake, th e refuge type was categorized as Â“unknownÂ”. If multiple refuge types were visible within a 2 m ra dius of a snakeÂ’s location, the structure nearest to the location was considered o ccupied. For gopher tortoise burro ws, if the signal was strongest from the burrow opening, I conclude d that the snake was in the tortoise burrow. A FisherÂ’s exact test was used to determine if males and fema les used refuges at different frequencies.
46 To further document the importance of fossorial refuges to pine snakes, when snakes were observed above ground, I recorded the presen ce or absence of three refuge types (pocket gopher mound, gopher tortoise burrow, and stumphole) within a 5 m radius of the snake. I recorded the same information for a second loca tion that was at a random distance (from 5 Â– 30 m) and azimuth (1 to 360 ) from the snakeÂ’s location. Ra ndom distances and azimuths were selected using a random number generator ( www.random.org ). A FisherÂ’s exact test was used to compare the presence and absence for refuges wi thin the 5 m radius of snake versus random locations. A simple t-test was used to compar e mean distances from snake locations versus random locations to the three refuge types. Results Habitat Associations and Microhabitat Use Florida pine snakes did not associate with a ny habitats at the home range scale (JohnsonÂ’s 3rd order, F0.05, 8, 4= 1.92; P = 0.276), i.e., Florida pine snakes used habitat within their home ranges relative to what was available. Howe ver, Florida pine snakes did exhibit habitat association at the landscape-scale (JohnsonÂ’s 2nd order, F0.05, 8, 4= 15.85; P = 0.009). A paired ttest comparing mean distances of random loca tions within-home range and across the landscape revealed that Florida pine snakes were most often associated with mixed pine-hardwood habitat (MX) ( F0.05, 1, 11= 7.01, P = 0.023), whereas all other habitats exam ined were used relative to their availability. An analysis of m ean distance ratios indicated that within home range locations were significantly closer to MX habitat than would be expected ac ross the landscape ( F0.05, 1, 11= 7.01, P = 0.023) (Figure 3-3). No habitats were avoided by pine snakes. The order of association as shown in a ranking matrix (Table 3-1), suggested that pine snakes selected for MX, followed by planted pine (PP), scrub/shrub (SC), wildlife food plots/agriculture ( AG), urban areas (UR),
47 hardwoods (HW), natural pine (NP), and wetlands ( AQ). At the microhabitat scale, Florida pine snakes used sites relative to what was available ( 2 = 2.16, df = 6, P > 0.90; Figure 3-4). Activity Patterns Activity patterns (as determined by frequency of above ground observations) of Florida pine snakes varied throughout the year. Snak es were observed above ground most often from March through July (Figure 3-5). They were also somewhat activ e in September and October. Breeding behavior was observed in late May and June. On 22 May 2008, I observed an unmarked male following within 1 m of a study fe male. On 12 June 2007, two male pine snakes, one of which was a study animal, were found atte mpting to copulate with an unmarked female. I observed a study female mating with a much smaller unmarked male on 19 June 2007, and on 25 June 2007, the same female was located within 1 m of a study male within a pocket gopher burrow. I observed Florida pine snakes feeding on two occasions during the study. A male snake was seen consuming a cotton rat ( Sigmodon hispidus ) in mid-July 2007; a second male was seen taking a juvenile cottontail rabbit ( Sylvilagus floridanus ) in early May 2008. I also x-rayed a female snake with a large prey item that was later identified based on dentition and body measurements as a southeastern pocket gopher (D Reed, Florida Museum of Natural History, University of Florida, pers. comm.). Lastly, in June 2008, a male pine snake that was held in the lab for transmitter removal at the end of the st udy regurgitated eight northern bobwhite eggs. Pine snakes were largely inactive during the winter (i.e. they were above ground at only 20% of observations), and made just a few shor t movements (Chapter 2). Basking was observed infrequently in winter (18% of observations) and typically invol ved the same two individuals, a male and the smallest female (64% of observatio ns for both). Snakes became more active in March (above ground in 33% of obs ervations) as average daily te mperature increased (Georgia
48 Automated Environmental Monitoring Network; www.griffin.uga.edu/aemn). Two individuals (male PM-6571 and female PM-3F3F), were radiotracked for two consecutive fall seasons and, though they did not use the same re fuge site each year, they over wintered within 335 m of their previous yearÂ’s hibernacula. Refuge Use Florida pine snakes were highl y fossorial in this study. They were located below ground at 76% of all locations and used a variety of belo w ground refuge sites, including burrows of ninebanded armadillo, mice ( Peromyscus polionotus and P. gossypinus ), southeastern pocket gophers, eastern wood rat ( Neotoma floridana ), and gopher tortoises, as well as stump holes. In this study, pine snakes were most frequently observed using pocket gopher burrows (62.5% of observations for both males and females; Figure. 3-3). All other refuges were used at much lower frequencies; these include d stump holes (M 5.7%, F 3.9%, tota l 5%), tortoise burrows (M 3.5%, F 1.6%, total 2.8%), armadillo burrows (M 3.9%, F 4.7%, total 4.2%), mouse burrows (M 2.6%, F 3.9%, total 3%) and various other refuges (M 1.7, F 0.8%, total 1.4%). I was unable to identify the refuge type for 21% of below gr ound locations (M 20%, F 22.7%) (Figure 3-6). I suspect that in many of these cases the snakes were in either a pocke t gopher burrow or other small mammal burrows, because old mounds and bu rrow entrances were often difficult to locate. There was no difference in the type of refuges used by males and females ( P =0.765). Snakes were not associated with any part icular refuge when they were above ground ( PPG=0.66, PTB=0.12, PSH=0.12 respectively). Pocket gopher bu rrows were present with a 5 m radius at 65% of snake locations versus 67% of random locations: tortoise burrows were present at 2% of snake locations as compared to 3% of random locations, and stump holes were present at 16% of snake locations versus 22% of random locations. I also found no significant difference
49 between the mean distance from snake locations versus random locations to the three refuge types: pocket gopher burrows ( P =0.09), tortoise burrows ( P =0.93), or stump holes ( P =0.68). Discussion Johnson (1980) suggested that animals may select habitat differently at different scales. In my study, Florida pine snakes exhibited landscap e scale habitat association, while at the home range scale, they did not associ ate with any habitat type. Furthermore, Florida pine snakes selected microhabitats relative to what was available. At the lands cape scale, Florida pine snakes were positively associated with mixed pine-har dwood habitat at the land scape scale, while all other habitat types, including natu ral pine, were used relative to their availability. Much of the MX habitat at Ichauway was subjected to hard wood removal prior to th is study. The impact of this removal on habitat selection in pine snakes is not known, however, in some areas, the MX habitat now more strongly resembles natural pi ne habitat. Ichauway land cover data are currently being updated and, once this is completed, a re-analysis of the data may be warranted It is unclear what factors driv e landscape scale habitat associa tion in Florida pine snakes. One possibility is prey availability. If prey co mposition of MX differed fr om other habitat types, it might explain the use of a particular habitat. My observations suggest Florida pine snakes take an array of prey as has been pr eviously reported in th e literature (see Er nst and Ernst 2003). However, the small mammal composition is sim ilar among the different upland forest types at Ichauway and prey population densities vary de pending on environmental factors rather than overstory composition (L.M. Conner and J.C. Rutledge, pers. comm.). Of the habitats considered, AG is the only habitat that has greater abundance in pr ey; yet pine snakes were not associated with this habitat. On occasion, I notic ed that pine snakes in this study used the edges of agricultural areas. However, the species ma y not use AG because it lacks suitable refugia and vegetative cover.
50 I suspect that refuge availability plays an important role in habitat selection in pine snakes. In this study, pine snakes were underground for 73% of all observations. They used pocket gopher burrows in at least 62.5% of below ground observations (Figure 3-6). Likewise, Franz (2005) reported that pine snakes were below ground for 81.1% locations and also exhibited an apparent preference for pocket gopher burrows. Pocket gophers also pres ent a food resource to pine snakes (Ernst and Ernst 2003). A recent report by the Georgia Department of Natural Resources (2008) concluded that Ichauway harbor s the largest concentra tion of southeastern pocket gophers in the state, hence, pocket gophe rs and their burrows are likely not a limiting resource for pine snakes at Ichauway. Unfo rtunately, pocket gopher density in the different upland habitats considered in this study is not known (i.e. mixed pine-hardwood habitat exhibiting the highest pocket gopher densities). Mounds prov ide evidence of pocket gopher activity; however, there is no clear way to relate mound activity to burrow or pocket gopher abundance. Northern pine snakes populations in New Jersey do not coexist with pocket gophers, but instead rely on the presence of other available refuges or create their own (at least for nesting purposes; Zappalorti et al. 1983). Surveys for Flor ida pine snakes in areas where southeastern pocket gophers have declined are badly needed. When above ground, pine snakes in this study were not closer to pocket gopher mounds than would be expected by chance, despite their apparent preference for th ese burrows as refuge sites. Pine snakes are large and mobile a nd may simply move through the landscape without regard for distance to a particular refuge type. However, it is also possi ble that an association was masked by the lack of independence between snake and random locations in this study (i.e. the 5-30 m radius for selection of random points may have been inadequate). This may have been remedied by using an alternate sampling tec hnique for selecting random locations, such as
51 selecting sites randomly across the landscape, rather than based on proximity to snake locations. The high population densities of pocket gophers at Ichauway also may mean that these refuge types are not limited. Repeating this study in areas where pocket gophers are less abundant may be more conclusive. One major difference between this study and Franz (2005) was the use of other refuge types. In this study, Florida pine snakes onl y infrequently used stump holes, gopher tortoise burrows, armadillo burrows and mouse burrows. Whereas in Florida, Franz (2005) reported higher rate of use of tortoise burrows and stum p holes (e.g., pine snakes in this study used tortoise burrows 5% as compared to 31% in Florida). This diffe rence may have been related to differences in tortoise and pocket go pher densities between the two sites. Also of interest in this study, was that radio-telemetered pine snakes never left Ichauway. Although the home ranges of several snakes bordere d off-site agricultural fields, these snakes were never detected entering this habitat. Snak es were also not observe d crossing either of the two major highways that bisect the property de spite five individuals having home ranges abutting them. They would, however, infrequently cr oss dirt roads. One male did cross a small, paved county road on several occas ions (spring movements), but th is is likely due to his home range being bordered by both a major highway and a large agricultural field, which minimized his ability to find mates and other resources. This tendency to stay within high quality habitat suggests that Florida pine snakes may be sens itive to highly distur bed and open areas. In this study, Florida pine snakes were most closely tied to mixed pine-hardwood forests, therefore managing for a hardwood component in upl and pine forest system s may be beneficial to Florida pine snakes. The presence of a natura lly occurring fire regime is likely important to ensure maintenance of this habitat. Relatively undisturbed, actively manage d sites like Ichauway
52 in southwest Georgia and the Katharine Ordway-Swi sher Memorial Preserve in Florida, are of great importance for pine snake conservation. More research on the sp ecies is needed to understand pine snake habits in lower quality ha bitats, specifically wh ere habitat is highly fragmented. Pine snakes also require ample re fuge resources, specifica lly southeastern pocket gopher burrows. It is critical to determine how the loss of pocket gophers might affect pine snake populations. Habitat loss and fragmentation is likely to continue in the region and the continued decline of pocket gophers for food and refuge may be paramount. Efforts are needed to conserve this species through the aquisition and proper management of upland habitats which ensure the presence of the resources nece ssary for Florida pine snake persistence.
53Table 3-1. Ranking matrix of Florida pine snake ( Pituophis melanoleucus mugitus ) habitat use at the land scape scale on Ichauway, Baker County, Georgia. Valu es are t-statistics ( P -values) associated with the pairwi se comparison of the mean distance ratio of random locations within home range to the mean distance ratio of random locations across the landscape. AgricultureHardwood Mixed Natural Pine Pine Plantation Scrub/ShrubUrbanizedAquatic Agriculture -0.50 (0.630) 2.08 (0.062) -0.57 (0.579) 0.55 (0.591) 0.98 (0.347) -0.04 (0.971) -1.16 (0.271) Hardwood 0.50 (0.630) 1.82 (0.096) -0.38 (0.711) 0.92 (0.379) 1.06 (0.314) 0.37 (0.716) -1.04 (0.323) Mixed -2.08 (0.062) -1.82 (0.096) -1.81 (0.097) -0.40 (0.698) -1.04 (0.322) -1.58 (0.142) -3.40 (0.006) Natural Pine 0.57 (0.579) 0.38 (0.711) 1.81 (0.097) 0.81 (0.433) 0.91 (0.380) 0.59 (0.570) -0.56 (0.585) Pine Plantation -0.55 (0.591) -0.92 (0.379) 0.40 (0.698) -0.81 (0.433) -0.15 (0.882) -0.72 (0.487) -1.22 (0.247) Shrub/Scrub -0.98 (0.347) -1.06 (0.314) 1.04 (0.322) -0.91 (0.380) 0.15 (0.882) -0.51 (0.622) -1.91 (0.082) Urbanized 0.04 (0.971) -0.37 (0.716) 1.58 (0.142) -0.59 (0.570) 0.72 (0.487) 0.51 (0.622) -1.15 (0.275) Aquatic 1.16 (0.271) 1.04 (0.323) 3.40 (0.006) 0.56 (0.585) 1.22 (0.247) 1.91 (0.082) 1.15 (0.275)
54 Figure 3-1. Landscape scal e habitat selection for a Florida pine snake ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. A mean of the distances to the nearest edge of each habita t type for random locations within the home range (n = 1,000 per snake home range) are compared to the mean distances of random locatio ns (n = 10,000) across the study site.
55 Figure 3-2. Landscape study sites selected fo r landscape random point generation based on locations of Florida pine snakes ( Pituophis melanoleucus mugitus ) on the Ichauway property, Baker County, Georgia. The Gray fill indicates area s used in landscape analysis of habitat association wh ile areas in white were ignored.
56 Figure 3-3. Mean distance ratios (1 SE) for la ndscape and within home ra nge scale habitat use across eight distinct habitat t ypes for Florida pine snake ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. Mean distance ratio s that are negative signify snakes being closer to habitat and positive signify snakes were further from habitat. The asterisk denotes statistica lly significant associ ation for mixed pinehardwood habitat at the landscape scale.
57 0 10 20 30 40 50 60 70 80 90Cano p y B a r e Ground Litter Co ar se Woody D eb ri s Wo o dy Herbs Grasse s% Cover Snake Random Figure 3-4. Microhabitat us e by 12 radio-instrumented Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.
58 0 10 20 30 40 50J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e cMonth% of observations Above ground Unknown Figure 3-5. Activity patterns of Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia.
59 0 10 20 30 40 50 60 70A rm a dil lo Mouse P oc ket G ophe r Woodrat Tort oi s e S t umphol e O t her UnknownRefuge types% Time in Refuge Figure 3-6. Refuge use by 12 radio-in strumented Florida pine snakes ( Pituophis melanoleucus mugitus ) at Ichauway, Baker County, Georgia. Refuge types included burrows of nine-banded armadillo ( Dasypus novemcinctus ), mouse ( Peromyscus spp.), southeastern pocket gopher ( Geomys pinetis ), wood rat ( Neotoma floridana ), and gopher tortoise ( Gopherus polyphemus ), as well as stumpholes.
60 CHAPTER 4 CONCLUSIONS AND MANAGEMENT IMPLICATIONS This study addressed questions regarding resource requirements of the Florida pine snake ( Pituophis melanoleucus mugitus ). The natural histor y of the Florida pine snakes is poorly known relative to that of its northern counterpart, P. m. melanoleucus (Burger and Zappalorti 1986, 1988, 1989, 1991; Burger et al. 1988; Zappalorti and Burger 1985), yet there is concern about possible declines in Florida pine snake popul ations (Franz 1992). To evaluate the status of Florida pine snakes, specific da ta on habitat associations and ar ea requirements were needed. Therefore, in this study, I estimated home ra nge size and habitat use across multiple spatial scales. Florida pine snakes are thought to be closely associated with southeastern pocket gophers, both for food and refuge; ther efore, I also examined refuge use. The impetus of this research was to evaluate aspects of the ecology of Florida pine snakes that are needed for development of management and conser vation strategies for this species. The results of the home range por tion of this study suggest that Florida pine snakes use moderate to large areas within second growth longleaf pine forest/hardwood matrices. The average overall home range size was 59.2 ha (b ased on MCP data) and varied greatly among individuals (n= 12; range 18.6 Â– 156.8 ha). Altho ugh factors driving home range size of Florida pine snakes are not clear, as one of the larges t snake species in North America (Ernst and Ernst 2003), they undoubtedly require larg e areas for procuring resour ces such as food, mates and refuge sites (e.g., Gregory 1984). Given that pine snakes in th is study were highly fossorial (76% of all locations), refuges for hibernation and daily cover may serve as a determinant of home range size and habitat use. Snakes in this study spent a large majority of their time underground within pocket gopher burro ws (62.5% of fossorial locations). Therefore, presence
61 of this species may strongly influence pine snak e populations. More research is needed on pine snake habits in areas with limited pocket gopher populations. In some snake species, home range size is in fluenced by sex or body size (see Macartney et al. 1988), though this is not genera lly the case (Gregory et al 1987) Although such an influence was not detected in this study, small sample size may have masked a difference. It would be useful to follow more individuals of different size cl asses (including hatchlings and juveniles) and a greater number of female pine snakes to determine if a difference truly exists. It is possible that different size cl asses require different resources throughout the landscape. Home range size differed among seasons in this st udy. Reproduction likely ha s a strong influence on home range size in pine snakes in spring and summer. Males had significantly larger home range areas in spring than in summer and fall/winte r. In this study, several males traveled up to 2 km, from their core home range s during breeding season, presumab ly in search of mates. This study suggests that in a forested upland landscape, management for a mixed pinehardwood matrix would benefit Florida pine sn akes. Maintenance of a mixed pine-hardwood community in southeastern forest s requires use of pres cribed fire or other means of preventing succession toward a hardwood dominated forest (N oss and Peters 1995). Fire also promotes growth of ground cover vegetation (Goebel et al 2001), which may offer effective cover from predators and thermal extremes. Burning also establishes an open canopy, providing substantial basking habitat for snakes. Prescribed burni ng may benefit southeastern pocket gophers by providing preferred forage and creating stump holes for refugia (Means 2005). Though stump holes were not often used by pine snakes, their presence may be beneficial to other species, including prey. By managing ha bitat, resources required by pine snakes would be encouraged
62 and perpetuated. Management for rare upland species such as the red-cockaded woodpecker ( Picoides borealis ) would likely ensure that pine snak e conservation needs are met as well. Portions of the mixed pine-hardwood habitat at Ichauway have been subjected to recent hardwood removal to allow reintroduction of pr escribed fire. However, I was unable to determine what influence this management activ ity may have on pine snake habitat selection. The hardwood removal areas that were used by pine snakes were structural ly similar to natural pine habitat, exhibiting dense ground vegetation with moderate to open canopies as well as the presence of ample refugia. Florida pine snakes used pocket gopher burro ws more than any ot her available refuge resource. According to a recent population surv ey of gophers in Georgia (Georgia Department of Natural Resources 2008), it was determined that Ichauway had the largest remaining population of southeastern pocket gophers in Geor gia, but elsewhere in the state their numbers have declined dramatically. Pocket gophers ma y be an important keystone species providing refuge (and food) for a variety of species including pine snakes (J Ozier, Georgia Department of Natural Resources, pers. comm.). Action should be taken to conserve populations of pocket gophers, which in effect would benefit pine sn akes, and other upland species that use their burrows. Despite their use of moderately disturbed ar eas, such as hardwood removal sites and small agricultural plots, Florid a pine snake home ranges were rema rkably restricted to Ichauway. Snakes rarely approached highly disturbed, offsite areas such as the center pivot irrigation fields, or developed areas. Florida pine snakes may avoid these areas because of the absence of refuges or because they lack suitable cover. Moreover, Florida pine snakes were never detected crossing the two major paved highways, even though several of the snakes had home ranges that abutted
63 them. Large agricultural fields and high use paved roads may effectively limit movements of Florida pine snakes, thereby decreasing geneti c exchange among populations. Use of smaller agricultural fields with hedgerows may help to facilitate movement of snakes between habitat patches, thereby decreasing isolation of popula tions in these landscapes. Roads have been determined to fragment habitat for wildlif e (Smith and Dodd 2003, Dodd et al. 2004), allow dispersal of exotic species (Seabrook a nd Dettmann 1996, Stiles and Jones 1998), and cause direct, and sometimes substantial, morta lity (Ashley and Robinson 1996, Rudolph et al. 1999, Shine et al. 2004, Smith and Dodd 2003). Use of ecopassages (Dodd et al. 2004) may facilitate movements of pine snakes across large highways, although research is needed to determine the effectiveness of such structures for large snakes It is unclear how re strictive roads and other land developments are to pine snake movements, s uggesting that implications of such structures should be considered for conservation purposes. A number of southeastern snake species are thought to be in dec line (Krysko and Smith 2005, Rudolph and Burgdorf 1997, Tuberville et al. 2000). Habitat loss and fragmentation are implicated to be a main cause of these decl ines (Dodd 1987, Gibbons et al. 2000). To stem the decline of Florida pine snakes, remaining tracts of native forest should be protected (e.g., placed in conservation easements or acquired by state and federal agencies). On existing protected areas, land owners and managers should incorporat e scientifically proven management practices, such as prescribed burning. Allowing a compone nt of hardwoods to occur within upland pine forests should be encouraged. Where possible, fragmentation of quality habitats should be minimized. Efforts should be made to protect re fuge resources; this would include fostering southeastern pocket gopher populations as well as leaving stumpholes and other fossorial cavities. Wise management on both public and private lands will be needed if we are to
64 perpetuate the long-term survival of Florida pi ne snakes and the rest of our unique wildlife heritage.
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72 BIOGRAPHICAL SKETCH Gabriel Â“GabeÂ” Miller was born a nd raised in southeast Minn esota. During his childhood he showed great interest in natu re and enjoyed many trips to his uncleÂ’s farm situated above the hills and bluffs of the Mississippi River vall ey. After graduating in 1995 from Lincoln High School in Lake City Minnesota, he attended Cent ral Lakes College in Brainerd, Minnesota where he earned an A.A.S. degree in natural resour ce technology in 1998. He earned his B.S. in wildlife management in 2003, at the University of Wisconsin-Stevens Point. His interest in reptile conservation started when working with the Minnesota Department of Natural Resources on wood turtle ( Glyptemys insculpta ) conservation. He took his interest to the University of Florida in Gainesville where he c onducted his thesis research on Fl orida pine snakes. He earned his M.S. in wildlife ecology and conservation in 2008. Gabe is currently married and is the proud father of a young son.