Terrestrial habitat selection by the dusky gopher frog (Rana sevosa)

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
John Allen Tupy (Creator)
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Joseph Pechmann

Abstract: The endangered dusky gopher frog (Rana sevosa) inhabits underground refuges created by fire and burrowing animals in longleaf pine forests. Prescribed fire can result in a mosaic of habitat patches having different characteristics. Fire suppression may lead to fewer underground refuges due to decreased disturbance and a reduction in vegetation required by burrow-making animals. I examined terrestrial refuge and prey availability as well as habitat choice of dusky gopher frogs (Rana sevosa) in a longleaf pine (Pinus palustris) forest (Harrison County, MS) managed with winter and early spring fires. In the first study I hypothesized that gopher frogs selected terrestrial home sites characteristic of well burned habitat. I tracked 13 adult and 4 juvenile gopher frogs from a breeding/metamorphosing site to terrestrial burrows using radio telemetry. I then characterized habitat at home sites and at randomly-chosen sites. In the second study I hypothesized that newly- metamorphosed gopher frogs would not be able to find appropriate underground refuges as quickly in fire-suppressed habitat as in well-burned habitat. I tested this by releasing captive-reared newly-metamorphosed gopher frogs into 15 x 15m terrestrial field enclosures in fire-suppressed or well-burned longleaf pine habitat. I used fluorescent powder to track the distance traveled by individual frogs before passing within 1 cm of an appropriate underground refuge, defined as any ground depression at least 2 cm deep and 1 cm wide. In the third study I hypothesized that fewer prey are available to gopher frogs in fire-suppressed habitats. I tested this by allowing newly- metamorphosed gopher frogs to forage in small cages in fire-suppressed and well-burned habitats, and then collecting their feces. I then sampled arthropods using fly paper at the same locations. Vegetation characteristics and soil moisture levels were measured at each release site. In the first study, average distance traveled, measured from the center of the pond, was 158.22m (std. dev. = 52.02, min = 94.3m, max = 239.6m). Nonmetric multidimensional scaling of habitat variables revealed that the gopher frog home sites grouped together when plotted. Compared to random sites, gopher frog home sites had a higher percent cover of grass and bare ground and a lower percent cover of shrubs and leaf litter, more underground refuges (mostly stump holes and small mammal burrows), and a more open canopy . In the second study, mean distance to a refuge was significantly lower in well-burned habitat (well-burned mean = 4.34 m ± 0.18 SE, fire-suppressed mean = 7.6 m ± 1.08 SE). The proportion of frogs tracked at least 6.05 m that found a refuge was significantly higher in well-burned habitat (well-burned = 0.88 ± 0.065 SE, fire-suppressed = 0.32 ± 0.091 SE). Foraging success as measured by mean feces weight did not vary significantly between habitat types in the third study (Exp. 1: p = 0.53, Exp. 2: p = 0.83). The mean number of arthropods captured was significantly higher in well-burned habitat than fire-suppressed habitat for experiment 1 (p < 0.0001), but not for experiment 2 (p = 0.39). Total vegetation cover, herbaceous cover and soil moisture were significantly higher in well-burned habitat. Shrub cover was significantly higher in fire-suppressed habitat. I conclude that animals that have a small home range may select patches with particular characteristics within a fire-maintained area because the animals require a specific microhabitat The habitat characteristics found at gopher frog home sites are associated with the effects of fire. Reduced availability of refuges in fire-suppressed habitat may decrease the survival of newly-metamorphosed gopher frogs emigrating from ponds. I found little evidence of differences in prey availability between well-burned and fire-suppressed sites that would influence habitat selection, but sampling was limited. The selection of characteristics by and benefits to gopher frogs influenced by fire suggests that more frequent or intense fires, or applying fire during the growing season, may increase the availability of preferred microhabitats.

Additional Information

Language: English
Date: 2012
fire, gopher frog, longleaf pine, mississippi
Frogs -- Effect of fires on -- Mississippi
Frogs -- Habitat -- Mississippi
Frogs -- Ecology -- Mississippi
Fire ecology -- Mississippi

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