Field Guide: A Chorus of Calls

by Sophia Wagner, Conservation Intern

Last month the Conservancy’s conservation team took part in North Carolina Wildlife Resources Commission’s Calling Amphibian Survey Program. BHIC’s previous conservation intern and budding herpetologist, Kylie Hackett, got the organization involved with this citizen science project in Fall of 2021. Frogs and toads serve a very important ecological role as a food source for many animals on the island. Amphibians are good indicators for ecological health as they are very susceptible to changes in the environment such as temperature and pollutants which they can absorb through their water-permeable skin. We went out at dusk to different locations around the island to observe and listen to calls, croaks, and quacks and record what we heard. Although we have many frog and toad species on the island, in June we only heard three different species of frogs and toads: the Green Tree Frog, the American Bullfrog, and the Southern Toad. Scroll down to look at my illustrations of each species and to learn a bit more of the most abundant species on Bald Head Island.

The American Green Tree Frog, Hyla cinerea, can be bright green, gray green, or yellow green and its colors can change based on their activity levels and external temperatures. Their size ranges between about 1.25 – 2.5 inches in length. During the day, these frogs usually rest in damp shady places and at night they do most of their hunting insects and other invertebrates and vocalizing. The frog call sounds similar to a yapping dog and makes sort of a “squak squak squak” sound. They call and breed from April to September. New research suggests that green tree frogs can pump their lungs full of air to reduce the noise of other frog species allowing them to hear their own species calls better. Green Tree Frogs mate from March to October and females can lay up to 400 eggs in shallow water and the males can fertilize the eggs. It takes about a week for the egg to hatch and two months until the tadpole develops into an adult frog. Green Tree Frogs can live for up to 6 years.

The American Bullfrog, Lithobates catesbeianus has green and/or grayish brown skin with brown spots and have round eardrums called tympanums on both sides of their head. The American Bullfrog ranges in size between 3.5 to 6 inches (not including their legs) and weighs around 1.1 pounds. American Bullfrogs are nocturnal ambush predators. Their strong hind legs allow them to jump and lunge at their prey and their large mouths allow them to fit and eat insects, mice, fish, birds, and snakes. They are capable of leaping 3 to 6 feet. Female American Bullfrogs are slightly larger than males. Males are highly territorial and aggressive regarding their territory. Only male bullfrogs croak and it sounds like “jug-o-rum” or kind of like the sounds of a lightsaber moving through the air. The males call late spring through early summer to attract mates.

The Southern Toad, Anaxyrus terrestris, are stout nocturnal omnivores that eat really anything they can find. “Anaxyrus” comes from the Greek word which means “A king or chief” and “terrestris” is Latin for “of or belonging to the earth.”  They are usually 1.5 to 3 inches long and are tan, brown, and gray with splotches. The skin of the toads is bumpy and has multiple warts within the dark spots. Southern Toads can be found burrowing in sandy soils. In breeding seasons they move to lowland bodies of water. The Southern Toad call sounds like a long high octave musical trill. Southern Toads usually call and mate from February to May, but may also call throughout the summer depending on rainfall. The call ranges from 2-8 seconds and is very rapid, with some as frequent as 75 trills per second. They are most commonly heard from March to October. Toads lay their eggs in a line while frogs lay their eggs in clumps. Southern Toads can live for 10 years and are inactive in late fall and winter.

If you are interested in hearing these species out in Bald Head Island I recommend going to the Wildlife Overlook, Stede Bonnet ponds, Kent Mitchell Trail, and by the Timmons Oak.

Sources Cited:

“American Bullfrog.” Retrieved from  https://ufwildlife.ifas.ufl.edu/frogs/americanbullfrog.shtml.

Animals. “American Bullfrog | National Geographic,” October 10, 2010. Retrieved from  https://www.nationalgeographic.com/animals/amphibians/facts/american-bullfrog.

“Green Treefrog.” Retrieved from  https://www.ncwildlife.org/Learning/Species/Amphibians/Green-Treefrog.

“Green Treefrog – Hyla Cinerea – NatureWorks.” Retrieved from  https://nhpbs.org/natureworks/greentreefrog.htm.

“Hall – The American Bullfrog Is the Largest Frog Species .Pdf.” Retrieved from  https://www.ncwildlife.org/Portals/0/Learning/documents/Profiles/Amphibians/American_Bullfrog_Wildlife_Profile_UPDATE.pdf.

Hall, Jeff. “The American Bullfrog Is the Largest Frog Species in North America.,” n.d., 2.

“NCCASP-Anura-Calling-Seasons.Pdf.” Retrieved from  https://files.nc.gov/ncparks/37/NCCASP-Anura-Calling-Seasons.pdf.

Florida Museum. “Southern Toad,” November 30, 2018. Retrieved from  https://www.floridamuseum.ufl.edu/discover-herps/florida-frog-calls/southern-toad/.

“Southern Toad.” Retrieved from  https://www.ncwildlife.org/Learning/Species/amphibians/southern-toad.