Kiersten Nelson
PhD Candidate at The University of Georgia, Savannah River Ecology Laboratory
November 2024
The Gopher Frog (Rana capito) has experienced widespread population declines across its range and is a species of conservation concern in all states in which it occurs. In addition, the U.S. Fish and Wildlife Service is considering the Gopher Frog for federal protection under the Endangered Species Act.
The Gopher Frog is native to the southeastern U.S. Coastal Plain and is associated with the longleaf pine ecosystem (Conant and Collins 1991; Palis and Fischer 1997). Adult frogs spend most of their lives in fire-maintained longleaf pine uplands (Humphries and Sission 2012), where they occupy underground refugia such as stump holes and Gopher Tortoise or small mammal burrows (Lee 1968; Richter et al. 2001). Unfortunately, the drastic loss of longleaf habitat throughout the southeast (Noss and Scott 1995) has also contributed to the decline of many species that live in longleaf habitat, such as the Gopher Frog.
Headstarting is the primary conservation strategy to assist with population augmentation and reintroduction efforts for the Gopher Frog. Headstarting involves collecting eggs from the wild, rearing the tadpoles in captivity, and then releasing the newly metamorphosed frogs back into the wild to supplement declining populations. Headstarting is expected to facilitate population persistence by protecting the vulnerable larval stage and increasing the probability of survival to metamorphosis (Dodd 2005). Gopher Frog headstarting efforts have successfully protected this vulnerable larval stage, but what happens to the juveniles after we release them back into the wild? We know very little about what happens to juvenile frogs after release, but the few studies that have looked at this have found low juvenile survival (Roznik and Johnson 2009; Hunt 2019).
Current headstarting protocols involve releasing newly metamorphosed Gopher Frogs on the surface, typically near the wetland edge. However, Gopher Frogs that spend more time aboveground have a higher risk of predation (Roznik and Johnson 2009; Roznik and Reichling 2021; Castellon et al. 2022). In addition, releasing juvenile Gopher Frogs into Gopher Tortoise burrows instead of at the wetland edge has been shown to reduce movement and increase survival (Roznik and Reichling 2021). For my research, I was interested in evaluating if juvenile survival could be improved with alternative release methods that aim to increase underground refugia occupancy and reduce movement.
For this study, I examined the effects of alternative release strategies including altering the time of year and age at release on juvenile movement, behavior, and survival. To do this, I conducted two radio-telemetry studies where I attached transmitter belts to juvenile headstarted Gopher Frogs to collect data on movement and survival. The first tracking period was conducted in the summer of 2023, when we tracked 32 newly metamorphosed (about 1-month-old juveniles) headstarted Gopher Frogs. The second tracking period was conducted in the winter of 2024, when we tracked 31 approximately 6-month-old juvenile headstarted Gopher Frogs. In both cases we tracked the frogs for two to three weeks. With financial support from The Orianne Society, I was able to purchase transmitters for the winter radiotelemetry study. This allowed me to compare the two tracking periods to understand how the time of year and age at release affected movement and survival.
For both tracking periods, all frogs were released into artificial burrows that we made by hammering a small metal conduit into the ground. My research was conducted in an area of South Carolina where Gopher Frogs and Gopher Tortoises do not co-occur. Thus, I was curious if Gopher Frogs would use artificially constructed burrows. If so, artificial burrows could be an alternative release strategy for areas without Gopher Tortoises or ample underground refugia that the species relies heavily on for survival.
Overall, my preliminary results are encouraging. In both the summer and winter tracking periods, juvenile survival was relatively high (> 60%) during their first two weeks in the terrestrial habitat. While survival was comparable between frogs released in the summer and the winter, I found differences in movement patterns. Frogs released in the summer tended to move more frequently and travel longer distances compared to frogs released in the winter.
I also found that the juvenile Gopher Frogs would occupy the artificial release burrows for long periods of time. I often observed resting pads just outside of the artificial burrows, where frogs would rest and feed on insect prey items. In addition, the frogs showed evidence of site fidelity to their release burrows. I observed several frogs in both the summer and winter tracking periods abandon their burrow and eventually return to the exact burrow that they were originally released in!
In the coming months, I will continue to wrap up data analysis for this project. Overall, the results from this study will inform future conservation efforts by making recommendations on release strategies that will improve the success of Gopher Frog headstarting programs.
This project was supported by funding from The Longleaf Alliance, The U.S. Department of Energy, The U.S. Fish and Wildlife Service, and The Orianne Society.
Literature Cited
Castellón, T.D., A.C. Deyle, A.L. Farmer, J.M. Bauder, E.A. Roznik, and S.A. Johnson, 2002. Effects of Translocation on Gopher Frog Survival and Movement. Herpetologica 78:161–168.
Conant, R., and J.T. Collins. 1991. A Field Guide to Reptiles and Amphibians, Eastern and Central North America. Houghton Mifflin Company, New York, New York, USA.
Dodd, C.K., Jr. 2005. Amphibian conservation and population manipulation. Pp. 265–270. In Status and Conservation of U.S. Amphibians. Lanoo, M.J. (Ed.). University of California Press, Berkeley, California, USA.
Hunt, J.D. 2019. Improving monitoring and habitat assessment for gopher frogs (Rana [Lithobates] capito) management in Georgia. Thesis, University of Georgia, Athens, Georgia, USA.
Humphries, J.W., and M.A. Sisson. 2012. Long distance migrations, landscape use, and vulnerability to prescribed fire of the Gopher Frog (Lithobates capito). Journal of Herpetology 46:665–670.
Lee, D.S. 1968. Herpetofauna associated with central Florida mammals. Herpetologica 24:83–84.
Noss, R.F., and J.M. Scott. 1995. Endangered Ecosystems of the United States: A Preliminary Assessment of Loss and Degradation. U.S. Department of the Interior, National Biological Service, Washington DC, USA.
Palis, J.G., and R.A. Fischer. 1997. Species profile: Gopher Frog (Rana capito spp.) on military installations in the southeastern United States. Technical Report SERDP-97-5, U.S. Army Engineers Waterways Experimental Station, Vicksburg, Mississippi, USA.
Richter, S.C., J.E. Young, R.A. Seigel, and G.N. Johnson. 2001. Postbreeding movements of the Dark Gopher Frog, Rana sevosa Goin and Netting: implications for conservation and management. Journal of Herpetology 35:316–321.
Roznik, E.A. and S.A. Johnson. 2009. Burrow use and survival of newly metamorphosed gopher frogs (Rana capito). Journal of Herpetology 43:431–437.
Roznik, E.A. and S.B. Reichling. 2021. Survival, movements and habitat use of captive-bred and reintroduced dusky gopher frogs. Animal Conservation 24:51–63.