Nicole Stevens, Chesapeake Conservation Corps Member
“Yaup, yaup, yaup,”
Said the croaking voice
of a Frog;
“A rainy day
In the month of May,
And plenty of room in the bog.”
“The Chorus of Frogs”
It’s May and spring is well underway! Trees have erupted bright green leaves and the ground is now carpeted in wildflowers. The forest teems with life once again, from tiny insects crawling around the leaf litter, to majestic osprey soaring overhead. Throughout April, green frogs and American toads were some of our predominant amphibian breeders, but now more froggy friends are leaving their hibernation to splash into our ponds and temporary pools.
Frogs play an essential role in global food webs, benefitting ecosystems (and even humans!) in many ways. Even before they turn into frogs, tadpoles help pond and wetland ecosystems by consuming algae, thereby maintaining good water quality. Tadpoles may also eat aquatic insect larvae, limiting the number of adult mosquitos, farm pests, and other bothersome bugs that reach adulthood. Fully-grown frogs also eat many insects, including many pests and disease vectors, and may also eat snails, worms, or grasshoppers. Basically, anything that can fit in a frog’s mouth, they will eat! American bullfrogs, the largest frogs in Maryland, have been known to eat turtles, snakes, bats, rats, birds, other frogs, and many more animals.
In addition to controlling populations of other species, frogs also serve an important role in food webs by being prey for larger animals. Tadpoles and eggs are often eaten by spiders, wasps, dragonfly larvae, shrimp, fish, and turtles, and many birds, reptiles, and mammals rely on adult frogs as a source of food. Even humans in many parts of the world eat frogs, and bullfrogs are farmed for human consumption in the Americas and in Asia. Without frogs, there would be massive disruption to food web dynamics and human communities would lose an important source of protein.
At ACLT, amphibian monitoring efforts are underway! Some amazing volunteers have spent time over the last few weeks checking traps along drift fences to count, ID, and safely release animals. These traps work because the fences prevent the animals from walking or hopping directly to the pools and instead encourage them to fall into cans at either end where they rest until released by volunteers. So far, volunteers have found several green frogs, a spotted salamander, and a pair of mating frogs! Surveys will continue to be run for two weeks each month until the end of June.
Lots of spring peepers have been heard during periodic frog call surveys and many green frogs and gray treefrogs were spotted singing in one of our newly created vernal pools! More and more egg masses have been appearing in seasonal and permanent wetlands that have already or will soon result in the emergence of thousands of frog tadpoles and salamander efts. Many other frogs including green frogs and leopard frogs have been seen around several vernal pools, as have salamanders, newts, and even some other herpetofauna including a black rat snake and a box turtle! See what species you can see and hear in your community!
In the past two blogs, I have highlighted nine of the earliest species to begin their breeding periods (see Frog Blog #1 and Frog Blog #2). This month, I will provide information about the rest of the native frog species in Calvert County. These include the American bullfrog (Lithobates catesbeianus), the eastern cricket frog (Acris crepitans), green treefrog (Hyla cinerea), eastern spadefoot (Scaphiopus holbrookii), and the eastern narrowmouthed toad (Gastrophryne carolinensis). Keep reading to learn more about these species and to listen to their songs!
Additional Southern Maryland Frog Species Active During May
American Bullfrog (Lithobates catesbeianus)
The American bullfrog is the largest frog in North America and can be longer than 8 inches and weigh up to 1.5 pounds! They are usually green or tan in color, and small individuals are easily confused with the green frog (Lithobates clamitans). Both of these species have visible tympanums (round external ears) behind their eyes, which are much larger in males than in females. The two species can be differentiated by the placement of their dorsolateral ridges (raised lines on their backs) which run down the entirety of the green frog’s back and curve around the tympanum in the bullfrog.
The American bullfrog is one of the last frog species in the US to emerge from hibernation (likely active in May or June in Southern Maryland) and they breed in permanent bodies of water where they lay up to 20,000 eggs at a time. They are unlikely to be found at ACLT’s vernal pool sites, but possibly closer to or in Parkers Creek or in permanent bodies of water in your neighborhood! Listen for their loud, low pitched “roo-roo-room,” or “jug-o-rum” call in summertime ponds: American Bullfrog Call
Eastern Cricket Frog (Acris crepitans)
The eastern (or northern) cricket frog is a very small species – growing just 1 inch long! They have slightly bumpy skin and are a type of treefrog, though they are not very good climbers compared to many of their relatives. Cricket frogs have quite a bit of color variation – ranging from light to dark green, or tan to dark brown – but usually have a characteristic “Y” shape running down their backs and a patch on their snout of the same color. They may be hard to find due to their small size, but reside in sunlit areas near the edges of permanent bodies of water including ponds and slow-moving streams where they opportunistically feed on insects. The call of a cricket frog sounds a bit like two marbles rubbing together: Cricket Frog Call
Green Treefrog (Hyla cinerea)
The green treefrog can be identified by its bright green coloration and frequently has a black and cream-colored stripe running down its side, though they can also be dull green, yellow, or gray depending on their environment or activity level. While other Maryland treefrog species – such as the gray treefrog – can be green, the green treefrog can be differentiated by its more oblong body shape and smooth (not bumpy) skin. Green treefrogs can reach up to 2.25 inches in length and females are often larger than males. They are a fairly common species throughout the southeast, though they are most plentiful in the coastal plain region where they breed in permanent ponds, wetlands, or streams that are generally quite sunny and have large amounts of foliage and floating plant matter. Green treefrogs are often found on or around homes where they eat insects drawn to evening lights. They are great to have around to help control meddlesome mosquitos and other irritating insects! Listen for their “reeenk reeenk reeenk” call to know they’re nearby, as it often indicates that rain is approaching: Green Treefrog Call.
Eastern Spadefoot (Scaphiopus holbrookii)
While eastern spadefoot toads are not an endangered species, they are less common in their northern range (from Virginia to Massachusetts) and primarily reside underground, so they are not spotted as often as many of the other frogs discussed in these blogs. Your most likely chance of seeing them is when they emerge from the ground in vast numbers to breed in temporary wetlands, puddles, and roadside ditches. Eastern spadefoots primarily breed during heavy rainstorms and otherwise remain buried in dry habitats with sandy soil. They grow to an average of 2.4 inches and have smoother, wetter skin than most toad species, though it is still visibly bumpy. The two most distinctive features of the eastern spadefoot are their back feet which are shaped like “spades” for digging and their bright yellow eyes with striking vertical pupils. If you’re lucky, you might get to hear their repeating “waaaah” call during the next rainstorm: Eastern Spadefoot Call.
Eastern Narrow-Mouthed Toad (Gastrophryne carolinensis)
The eastern narrow-mouthed toad is another uncommonly spotted species and has some behavioral similarities to the eastern spadefoot. They are a funny shape compared to many of southern Maryland’s other species, boasting a fairly flat body shape, pointy face, small mouth, and a skinfold behind their eyes which they can pull forward to block attacking insects. Eastern narrow-mouthed toads have heavily mottled undersides and can be gray, brown, red, or even black depending on the day and the individual’s mood. They can be up to 1.5 inches long and males can be differentiated by their darkly pigmented throats. Unlike most toads, they have smooth skin that lacks warts. Maryland is the northern tip of the narrow-mouthed toad’s range and they can live in a variety of conditions (including brackish water!) as long as they are moist and sheltered. Eastern narrow-mouthed toads are commonly found under logs in forested areas, or burrowed under other materials including leaf litter and even lawns. Listen for their long, high-pitched “waaaaaaaaaaaaaaaah” as they emerge during rainstorms to breed in temporary wetlands: Eastern Narrowmouthed Toad Call