Looking for Frogs in the Corkscrew Watershed

It was a warm, still evening in June when the crew gathered just after sunset at Audubon's Corkscrew Swamp Sanctuary for the first Frog Watch survey of 2026. Led by the Sanctuary's director of public programs, Sally Stein, the team of four volunteers included both seasoned experts and novice frog watchers. The goal? Conduct monthly surveys during the summer breeding season at pre-determined locations around the Sanctuary to record any frogs heard calling.

Founded by the Southwest Florida Amphibian Monitoring Network more than 25 years ago, Frog Watch is a diverse group of volunteers dedicated to monitoring frog populations and other amphibians in Collier, Lee, and Charlotte counties, tracking changes over time.

Why study frogs?

Many wetland species are directly affected by development, but few animals show these impacts as dramatically as amphibians. During the recent Corkscrew Watershed Science Forum, John Cassani and others with Florida Gulf Coast University described the results of 26 years of Frog Watch surveys across Southwest Florida, with local data echoing the global decline of these environmental indicators.

According to their data, at least three species are rarely or no longer heard calling across much of their historical range, including chorus frogs, gopher frogs, and Eastern spadefoot toads. It is well known that these animals are threatened by pollution, rainfall deficits, predation, and microbes, but species such as the pinewoods treefrog and Southern cricket frog have not been heard at the Sanctuary in many years.

The June survey

During the June survey, we drove to the twelve locations in the Frog Watch survey area (located within a 15-mile radius of the Sanctuary), where urbanization is ramping up. At each location, the team records the environmental conditions, including time, temperature, sky condition, noise code, water level, and any visible changes to the habitat.

Every location had varying degrees of traffic noise, and the sky was mostly clear with a crescent moon, but the team observed one constant: no water, and few frogs were calling. By the end of the evening, the team recorded one species, greenhouse frog (a nonnative species), being heard in eight of twelve locations. Additionally, we recorded a pig frog in five locations, plus overlapping oak toad calls at two locations (indicating more than one individual present), one cricket frog, and an actual chorus of green tree frogs (three or more individuals present). Only two locations had three species present — both were within the Sanctuary boundary.

Eight species were not recorded: barking treefrog, chorus frog, cricket frog, leopard frog, little grass frog, narrow-mouth toad, pinewoods treefrog, and Southern toad. With much-needed rainfall at the end of June, the next three surveys are likely to reflect better numbers. In fact, during a late-June guided night walk on the boardwalk, the group heard pig frogs, a chorus of green treefrogs, narrow-mouthed toads, oak toads, and greenhouse frogs.

Why this matters

Frogs are nature's pest controllers and environmental sentinels. They consume vast numbers of insects—including mosquitoes—while providing food for birds, snakes, fish, and other wildlife. Because they serve the ecosystem both as predator and as prey, their health reflects the health of the environment we share.

For more than a century, Audubon has been working to secure and preserve the habitats birds rely on, like Corkscrew Swamp Sanctuary, for their breeding, migration, and other essential needs. Frogs are an important part of their world, and ours.