Wood Frog


The tiny but tough wood frog can be found in woodland ponds and forested habitats across the northern half of North America.

Listed as a Species in Greatest Need of Conservation in the Illinois Wildlife Action Plan, the wood frog is a species that Peggy Notebaert Nature Museum of the Chicago Academy of Sciences' biologists are working to monitor and restore to the woodland ponds of Illinois.

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About the Wood Frog

These unique frogs can survive even when 65% of the water in their bodies is frozen. Despite their tolerance for the cold Chicago weather, and even the Alaskan winters, the species is one of several pond-breeding amphibians that have lost much of their historic wetland habitat. Dr. Allison Sacerdote-Velat and her team at the Peggy Notebaert Nature Museum are working to preserve this species through careful monitoring of reintroduced populations of the frogs in Illinois. The team has been translocating wood frog egg masses to reestablish additional populations in historic sites that have been restored.

What are we doing to help?

For Dr. Sacerdote-Velat, wood frogs have been an important part of her amphibian work since 2004 when she began assessing a wetlands habitat for the reintroduction of the species. Following successful translocation of the frog eggs to the new site that had been hydrologically restored (or made to mimic the frogs’ needed water conditions), a wood frog monitoring program at the Nature Museum was born. As researchers keep an eye on the wood frogs that were reintroduced to the forest preserve as eggs, it’s important to look at many aspects of the frogs’ lives.

What our scientists monitor:

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.

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The Power of a Frog

It’s hard to believe how much one frog species can affect the ecosystem, but research shows the wood frog has notable contributions to its environment.

  • Wood frogs are early breeders, so the effects of their presence in the environment may be more pronounced. When wood frogs mate for the season, there are few competing species and wood frogs appear in large numbers in fishless ponds. Their breeding patterns affect the nutrients and energy levels in ponds, and their tadpoles affect the dynamics of the algae for species that arrive later in the season.
  • These frogs also play a key role in the predator and prey cycle within the habitat. They prey upon insects and soil arthropods and they are food sources for snakes and wading birds.
  • Wood frogs are part of a diverse amphibian community. When there are many species present, certain disease agents may be diluted, or spread, throughout the population, reducing the chance of spreading disease among frogs.
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Meet the Expert

Dr. Allison Sacerdote-Velat is the Curator of Biology & Herpetology/VP of Conservation Research at the Peggy Notebaert Nature Museum of the Chicago Academy of Sciences, conducting research focused on conservation and restoration of local reptiles and amphibians including the smooth greensnake and wood frog. Allison coordinates the Calling Frog Survey, a community science program that monitors amphibians across the Illinois region.

“Since the launch of our program in 2017, we have found over 200 wood frog egg masses in the site where we reintroduced the frogs – the greatest reproductive output we’ve seen in this species!”


Funders for the Peggy Notebaert Nature Museum’s work with the wood frogs include the Lake County Forest Preserve District, Illinois Department of Natural Resources State Wildlife Grant, Lincoln Park Zoo, Wildlife Grant Project, and the Virginia Military Institute.

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