Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Frog Call Survey: Music to Biologists’ Ears

June 12, 2024
Cuban Tree Frog Crop

Results of SCCF’s first frog call survey of 2024 that took place during a heavy rainstorm on June 3 were encouraging in terms of species that have bounced back since Hurricane Ian, except for the pig frog that was not heard.

Wildlife Biologist Mike Mills and Wildlife Biologist Intern Nadine Cobb headed out after sunset to visit monitoring stations throughout the island where they were met with music to their ears.

“After a very dry and hot late dry season in April and May, many wildlife species, particularly frogs, reacted explosively to the heavy downpour,” said Mills. “Sanibel erupted with the sounds of calling frogs, as puddles and other temporary wetlands filled with water.”

Frogs and toads were seen crossing roads throughout the survey with the rainfall, which unfortunately leads to widespread road casualties from traffic. Amphibians, such as frogs, salamanders, caecilians (limbless worm-shaped amphibians), are good indicators of environmental health due to their porous skin that absorbs moisture from the environment.

“Frog surveys are important because they can alert us to new issues with contaminants and/or toxins in wetlands due to the loss of frog diversity and quantity, particularly of certain sensitive species,” said Mills.

The rare squirrel tree frog, pictured here breeding, was heard at one site.

With the hot temperatures, the calls of several summer breeders could be heard throughout the island such as the eastern narrow-mouthed toad (Gastrophryne carolinensis), green tree frog (Hyla cinerea), and the exotic Cuban tree frogs (Osteopilus septentrionalis).

Even the rare squirrel tree frog (Hyla squirella) was heard at one site. Two toad species, the native southern toad (Anaxyrus terrestris) and the exotic cane toad (Rhinella marina) were heard, as well as a winter breeder, the southern leopard frog (Lithobates septentrionalis).

The small exotic greenhouse frog (Eleutherodactylus planirostris) was heard throughout the island.

“Frog species will call out of season from time to time with extreme weather conditions such as a large rain after a long period of drought, or unseasonably hot weather during the winter,” Mills explained.

The pig frog (Lithobates grylio), which was the species of most concern on the island after Ian, was not heard during these surveys. However, they were verified to be in existence through a frog call survey at the end of the 2023 wet season.

Before Hurricane Ian, they were considered to be wildly abundant on Sanibel and were consistently heard on frog call surveys.

“It took approximately a year to document the pig frogs’ continued presence on the island post-Ian. These were finally recorded on the far west end of the island last summer,” said Mills. “As the summer rains increase with frequency, we expect that we will hear the familiar call of the pig frog again.”


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