By Nicole Stevens, Chesapeake Conservation Corps Member
O, I love to hear the frogs
When they first begin to sing;
How they vocalize the bogs,
And vociferate the Spring.
How they carrol as they croak,
How they mingle jest and joke
With their solemn chant and dirge
On the river’s slimy verge.
– Harry Edward Mills, “The Early Frogs”
This is the first in a series of monthly blogs that will showcase progress on ACLT’s conservation and research efforts as well as highlight currently-active frog species. Stay tuned to receive updates! You may also wish to subscribe to our blog here: www.acltweb.org
After weeks of rain, snow, and freezing weather, spring has finally begun for some of our amphibian friends! On Saturday, February 27th, spring peepers were heard during an evening guided hike at ACLT – the first frog calls noted in 2021. Soon, many more of Maryland’s 20 native frog and toad species will join in these nighttime songs as each of their breeding seasons begins. So, who are the frogs we hear calling in the evenings? And what is ACLT doing to conserve and research these important species?
The word “amphibian” means “double life” and refers to a group of animals that have aquatic larval stages generally followed by terrestrial, or land-dwelling, forms. The class Amphibia encompasses the orders Caudata or Urodela (the newts and salamanders), Gymnophiona or Apoda (the caecilians; a group of burrowing worm-like creatures with slimy skin and no legs), and the most commonly known: Anura (the frogs and toads). Many of these species utilize seasonal wetlands (often called vernal or woodland pools) as breeding sites since these pools are generally dry for part of the year, making them uninhabitable for permanent aquatic predators like fish. During their mating season, male frogs will “sing” to attract females who will then deposit fertilized eggs at these seasonal pools, or sometimes into more permanent ponds. Frog eggs are usually found in loose clumps, while salamander eggs are usually attached to surfaces (like sticks or leaves), and toad eggs resemble beads on a string.
Frog breeding periods vary slightly each year depending on weather conditions like temperature and precipitation. In southern Maryland, there are four active frog species you may be able to see (or hear) in March: the spring peeper (Pseudacris crucifer), the wood frog (Lithobates sylvaticus), the upland chorus frog (Pseudacris feriarum), and possibly the pickerel frog (Lithobates palustris), though the latter will likely not be active until April. There also may be a chance to hear American toads (Anaxyrus americanus), but they also will most likely not be out until April and May. Links to hear the calls of these species and more information about them are included below! Try to figure out what species are in your neighborhood (though remember not to handle them as their skin is very sensitive and many species also secrete irritating toxins).
As one of the two Chesapeake Conservation Corps Members working at ACLT this year, I am focusing on amphibian conservation for the program’s capstone project. A few weeks ago, I was awarded grant funding by the Chesapeake Bay Trust to install two new vernal pools, create educational signage and activities, and perform drift fence and frog call biodiversity surveys. I am happy to say that with the help of six wonderful volunteers, including University of Maryland herpetologist, Dr. Christopher Rowe, the first vernal pool was installed on March 3rd! This site is near existing vernal pools along the PF2Bay trail that are heavily utilized by breeding amphibians, so it will offset breeding pressures experienced at these two sites.
A second vernal pool was installed on March 12th with the help of five volunteers! This seasonal wetland is slightly further from existing pools – creating a new breeding site to increase the range of these important species, many of which are threatened. Both manmade vernal pools were made by digging shallow depressions in naturally low areas and installing 15-foot by 25-foot pond liners. They will be filled with spring showers and may attract amphibians throughout the spring and summer. By installing pond liners, these woodland pools will serve as important breeding sites for frogs, toads, and salamanders for decades to come.
The first frog call survey was also completed on March 2nd and 3-4 spring peepers were heard calling, despite the weather only being 31˚F! Data for these surveys are reported to FrogWatch USA, a program run by the Association of Zoos and Aquariums to form a nation-wide database for researchers, conservationists, and other interested people.
Southern Maryland Frog Species Active During March (click to enlarge photos)
|Spring Peepers (Pseudacris crucifer)
Spring peepers are the first frog species to emerge from hibernation each year, due to the natural anti-freeze in their blood that makes them especially cold-tolerant. They are quite small (only 1-1.5 inches long), usually brownish or greenish in color, and have a dark X-shape on their backs. Spring peepers are a type of treefrog with smooth, slimy skin and terrific climbing ability, though they generally remain hidden in leaves and brush on the forest floor. Listen for their high-pitched calls near waterways or forests at dusk. Each frog may call more than 20 times per minute! Click to hear the Spring Peeper call.
Wood Frog (Lithobates sylvaticus)
Another frog species to leave hibernation early is the wood frog, which emerges in late February or early March, depending on weather conditions. Wood frogs are tan with an area of dark brown behind their eyes that resembles a mask. They are much bigger than peepers, growing up to 3.25 inches in length, and are obligate vernal pool species, meaning that they require temporary wetlands to breed and cannot coexist with many permanent pond-dwelling species. Wood frogs are explosive breeders that only mate for a few days out of the year and produce many eggs at once. They were spotted at ACLT on March 10th and some wood frog egg masses are visible in the vernal pool along the PF2Bay trail!
The coolest fact about the wood frog is that they are the only frog species known to live north of the Arctic circle and they survive the frigid winters using a unique series of adaptations. During hibernation, their hearts stop beating and they cease breathing as ice encases their bodies. They are able to survive using special compounds in their cells that prevent internal freezing and dehydration. In the spring, their bodies thaw and their breeding cycle begins. Listen for their quack-like calls in the evenings: Wood frog call.
|Upland Chorus Frog (Pseudacris feriarum)
The upland chorus frog is a small treefrog species that grows up to 1-3/8 inches and may begin breeding in late March in Southern Maryland. They are usually brown or gray with variable patterns, potentially including stripes or spots. However, they all generally have a dark stripe on each side of their bodies passing through their eyes and bumpy skin. Upland chorus frogs are more tolerant of anthropogenic disturbances than many other frog species, and may breed in human-generated habitats. Click to hear the Upland Chorus Frog call.
|Pickerel Frog (Lithobates palustris)
The pickerel frog is in the family Ranidae, meaning it is a type of “true frog” that has many adaptations for life in the water, including webbed feet, long legs, and the absence of toe pads that facilitate climbing. Pickerel frogs are generally 2-4 inches in length and are green or tan with a number of darker brown splotches. The pickerel frog resembles the leopard frog (also found in this region) but can be differentiated by its square-shaped spots and the bright yellow markings near its hips (easily seen when the frogs jump). They secrete a substance that is dangerous to their predators and can be irritating to humans, but this species is very beneficial to the ecosystem by consuming otherwise-dangerous insects. Pickerel frogs hibernate in muddy pond bottoms and are usually most active in April, though if you’re lucky you may hear some at the end of March! Their call sounds a bit like a human snore: Click to hear the Pickerel Frog call (with a chorus of spring peepers in the background)
|American Toad (Anaxyrus americanus)
The American toad is one of two true toad species found in southern Maryland. It is up to 4.4 inches long and has dry, bumpy skin and short back legs used for making small hops instead of the long leaps characteristic of most frog species. The American toad usually has 1-2 dark spots per colored patch on its body, differentiating it from the Fowler’s toad which generally has 3-4. In southern Maryland, American toads are usually active throughout April and May, though it is sometimes possible to hear them calling in late March. Look out for them in your nearby forests, or even your backyard! Click to hear the American Toad call.
For more information, check out these links:
Maryland’s Frogs and Toads (Order Anura) – Maryland DNR
Spring Peepers – The National Wildlife Federation
Upland Chorus Frogs – Virginia Herpetological Society
– Maryland DNR
Pickerel Frogs – Virginia Herpetological Society
American Toads – Animal Diversity Web