REPTILES
Using Predator-Exclusion Cages to Monitor and Protect Bog Turtle Eggs by Gabrielle Graeter,Western Region Herpetologist – Reptiles and Rosie Ronca, Herpetologist Technician
T he southern lineage of bog turtles (Glyptemys muhlenbergii) is both federally threatened (S/A) and state threatened, though currently not fully listed under the Endangered Species Act. With recent additional funding from a Competitive State Wildlife Grant, NCWRC staff and project partners have been working to collect additional data to provide a more comprehen- sive understanding of the species’ population status. One part of this project is quantifying recruitment of juvenile bog turtles into each population, while also improving the hatch success of eggs and survivorship of juveniles. For this effort, we must search for bog turtle nests, and at some bog sites, we collect eggs for our head-start program with Zoo Knoxville, and at other sites, we install predator exclusion cages to protect nests during incubation. The caging method allows eggs to develop on site with a reduced threat from preda- tors, thereby giving them a better chance of hatching in the wild. Both head-starting and caging methods enable us to conserva- tively estimate the number of hatchlings entering a population each year. However, bog turtle nests are very difficult to find, so there may be more nests than we are detecting at some bog sites. In June and July 2024, to increase our detection effort, NCWRC contracted Tulpehocken Habitat Management LLC to conduct bog turtle nest searches with us and other conservation partners. This assistance provided 4 weeks of consistent daily effort and resulted in 35 nests being found in 11 bogs, located in Alleghany, Ashe, Henderson, McDowell, and Wilkes coun- ties. Eggs were collected for head-starting at 7 of the bogs, and cages were used at 5 of the bogs (at one site half of the nests are collected for head-starting and half are caged, for the purpose of evaluating the program in the future). From our 5 caged sites, we were able to release 43 hatchling bog turtles; there were 14 eggs that did not develop or died during hatching. Through the caging and monitoring of these nests, we are not only ensuring that the eggs have a higher chance of survival to hatch but also gaining valuable information regarding nesting habitat selection and recruitment of juveniles into these pop- ulations. While surviving to adulthood is a challenging time for
bog turtles, and many won’t make it through the first few years of life, we were able to ensure more eggs hatched by reducing predation. As we are unable to head-start hatchlings from every population, the use of predator exclusion cages is highly valuable in helping these populations grow. We are excited to hopefully re-encounter some of these individuals in the future and have evidence of their survival!
NCWRC
NCWRC
Top: After finding a nest, a predator exclusion cage is built around the tussock microhabitat to protect the eggs from predators during incu- bation. It is removed after the eggs have hatched and the hatchlings have had time to absorb their yolk sac. Bottom: After hatching, every individual received a unique mark via a small notch on the shell to aid identification and monitoring. Individuals were then weighed and measured before release.
27 2024 Wildlife Diversity Program Annual Report
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