A regional scale assessment of habitat selection and home range of the eastern rat snake in pine-dominated forests
Introduction
The breadth of an animal’s movements and spatial ecology can be influenced by many factors, including reproduction (Bertrand et al., 1996, Gibbons and Semlitsch, 2001), food availability (King and Duvall, 1990, Mares et al., 1982, Shine et al., 2003), environmental conditions (Blouin-Demers and Weatherhead, 2001a, Blouin-Demers and Weatherhead, 2001b, Lillywhite, 2001, Webb and Shine, 1998), and habitat structure/resource availability (Gregory et al., 2001, Kie et al., 2002, Pasinelli, 2000). Given similar diet preferences and reproductive ecology within a species, habitat type and availability may have the largest influence on plasticity of space use across a species’ geographic distribution. Animals may need to travel longer distances if particular resources are limiting, possibly impacting survival, due to increased energy expense and predation risk (Gregory et al., 2001).
The biologically diverse longleaf pine (Pinus palustris) ecosystem was once the dominant habitat type across the Coastal Plain of southeastern USA. Currently, it is one of the most globally endangered ecosystems in North America (<5% remains), mainly due to conversion to agriculture and industrial pine plantations, urban development, and fire suppression (Noss et al., 1985, U.S. Department of Agriculture [USDA], Forest Service., 2016, Ware et al., 1993). In the absence of frequent fire, longleaf pine forests become hardwood dominated systems (Gilliam and Platt, 1999, Heyward, 1939). Species that require open canopy pine forests and abundant herbaceous ground cover, including the red-cockaded woodpecker (Picoides borealis, Rudolph et al., 2002), gopher tortoise (Gopherus polyphemus, Yager et al., 2007), and snakes, like the eastern diamondback rattlesnake (Crotalus adamanteus), and the eastern indigo snake (Drymarchon couperi) (Hoss et al., 2010, Hyslop et al., 2014) are thought to have declined in fire-suppressed forests. But other species, within the former range of the longleaf pine ecosystem associated with hardwoods, e.g., certain songbirds (Conner et al., 2002), raccoon (Procyon lotor, Kirby et al., 2017) and rat snakes (Pantherophis spp., Blouin-Demers and Weatherhead, 2001a, Blouin-Demers and Weatherhead, 2002, Fitch, 1963, Reinert, 1993, Stickel et al., 1980), may have benefitted from increases in hardwoods in pine forests. Eastern rat snakes (P. alleghaniensis) are predators of eggs and chicks of the northern bobwhite (Colinus virginianus), a popular gamebird species in the southeastern U.S. (Staller et al., 2005) and the federally protected red-cockaded woodpecker (Jackson, 1978, Neal et al., 1993). Hence, there is considerable interest in whether fire suppression may, indirectly, have resulted in increased populations of eastern rat snakes, as well as in identifying habitat restoration methods to minimize impacts of this native predator (Sash, 2007, Stapleton, 2005). Although historic data on eastern rat snake abundance are lacking, we suspected that snakes may use habitat resources differently across their range, especially in areas where management and restoration practices select against preferred habitats. Therefore, our objective was to investigate patterns in habitat use for eastern rat snakes across multiple pine-dominated forests. We focused on three managed pine forests in South Georgia and North Florida to capture regional and management-specific differences in eastern rat snake resource use.
Section snippets
Study area
We collected data on three privately-owned pine-dominated properties in southwest Georgia and northern Florida that were managed for restoration and conservation of southeastern pine forest endemic species (e.g. red-cockaded woodpecker, gopher tortoise) and northern bobwhite quail hunting. All three sites were managed with prescribed fire (1–3 year rotation) and hardwood removal to restore fire corridors and promote an open canopy pine forest with species-rich ground cover (Edwards et al., 2013
Home range, macrohabitat, and refugia selection (all sites)
Our analyses included data from 30 adult eastern rat snakes (9 from Ichauway, 10 from Tall Timbers, and 11 from Pebble Hill) radio-tracked from 37 to 495 days (Table 3). We excluded 4 snakes from analyses that had <12 locations due to loss of transmitter signal or a mortality event. We observed an average of 52.6 ± 14.9 locations on Ichauway, 23.8 ± 11.2 mean locations on Tall Timbers and 28.9 ± 12.9 mean locations on Pebble Hill (Table 3). Snakes at all sites exhibited some degree of site
Discussion
Ichauway home range estimates (13.6 ha) were not only 3.9 times larger than Tall Timbers (3.5 ha) and 2.6 times larger than Pebble Hill (5.3 ha) but were also much larger than estimates reported for sites outside of Georgia and Florida: [5.6 ha, Arkansas (Mullin et al., 2000), 9.5 ha, Maryland (Durner and Gates, 1993), 7.6 ha, Ontario (Weatherhead and Hoysak, 1998), 9.7 ha, Illinois (Foster et al., 2006), 5.6 ha, Illinois (Carfagno and Weatherhead, 2008)], with one exception [35.1 ha, 95%
Management implications
Our findings suggest that hardwood removal as a land management activity in longleaf pine dominated systems may affect eastern rat snake populations. Snakes on Ichauway re-used individual oak trees more often than at the other two sites and moved further between individual trees. We also noted large differences in captures of eastern rat snakes at traps among the three sites over the study period [e.g., 14 snakes at Ichauway (n = 16 traps), 154 at Tall Timbers (n = 15 traps) and 127 at Pebble
Declaration of interest
None.
Acknowledgements
We thank B. Schlimm, M. Dziadzio, B. O’Hanlon, T. Baldvins, A. Vicente, C. Oliver, C. Faidley, S. Lillie, R. King, A. Ballou, N. Smith, J. Murdock, S. Ruane, J. Danielson, and P. Hill for field assistance. We thank B. Rutledge and S. Jack for providing hardwood removal data. We thank L. M. Conner for statistical support, J. Brock for GIS assistance, and B. Howze, B. Rutledge, and J. Jensen for reviewing an earlier draft of this manuscript. Funding provided by the J.W. Jones Ecological Research
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