Wood Frog

Through live-trapping (a method of capturing that allows experts to observe a frog and then set it free) and photo identification the Museum’s experts can learn a lot about population dynamics and the species’ response to changing environmental conditions.

One of the ways researchers assess the population size and breeding effort for amphibians is through egg mass counts. Some species of amphibians, like the wood frog, lay large cohesive masses of eggs in their breeding ponds. The number of unique egg masses in a pond represents the number of breeding females in the pond. By having two observers conducting egg mass counts through the breeding window, we can track changes in the number of breeding females at a particular location, or as habitat quality changes. Female wood frogs often deposit their eggs communally (in one big group), but the unique egg masses are still distinct enough to count. Male wood frogs will float near the eggs and continue to call, trying to attract more female frogs to the area. The males are very territorial and will chase other males away.

Monitoring frog population health is vital. A pathogen called chytrid fungus is wiping out frog species worldwide. The Museum conducts surveillance to monitor for the prevalence of the disease and ensure it doesn’t spread. The research team alsomonitor frog stress levels through a simple, non-invasive swab of their skin to see if their baseline stress and disease incidence become lower as habitat quality improves through restoration.

From 2017-2021, the Academy’s research team translocated wood frog eggs to three sites where historic populations once occurred. These sites had been restored by removing invasive buckthorn shrubs, and creating light gaps in the forest canopy to promote oak tree growth. Each year, the research team examines egg hatching success and tadpole survival in the new sites, and monitors for disease. In 2023, the research team documented wood frogs breeding in two of the three study sites. These observations are early evidence of persistence and reestablishment of the wood frog populations.

Some of the ways climate change is expected to impact amphibian populations is through more frequent and severe drought, and more frequent and powerful storms that can produce flooding conditions. These precipitation-related factors impact the length of time that amphibian breeding ponds hold water, which affects whether tadpoles and salamander larvae survive to metamorphosis. In particularly dry years, amphibian breeding is often unsuccessful, and adult body condition may be impacted, with less food available. Our research team has been exploring the effects of the droughts that occurred in 2021, 2022, and 2023 on local amphibian fitness. The researchers are using egg mass counts to examine changes in breeding effort and success during and after droughts, examining whether amphibian body condition is affected by the preceding year’s conditions, and tracking changes in amphibian diversity before, during, and after drought.