Songs of Spring

Singing a Different Tune

What comes to mind when you think of the songs of spring? To many people, birds are the songsters of the natural world. The songs of American Robins can be heard at sunrise and sunset throughout the Hamilton area. Other species, like Carolina Wrens or Red-winged Blackbirds, may be what come to mind as the typical spring songbirds. However, some of the loudest singers at this time of year are frogs and toads. If you take the time to listen near healthy wetlands or ponds from late March to June, you might get a chance to hear some of their unique tunes.

Something to Sing About

Frogs and toads mainly sing to attract mates. Most frog species sing directly from the water body they will lay their eggs in, so the entire reproductive process can happen in one location. Male frogs use their vocal sac to increase the resonance and volume of their songs, inflating them with air from their lungs as they begin singing. This method of sound production is somewhat unique among vertebrates, as no air is expelled to produce sound. In contrast, the air cycles back and forth between the lungs and the vocal sac to continue to produce sound. While the males sing, females listen and locate the males with the best songs to mate with. Each species has a unique song, so hearing a frog can be as useful for identifying the species as seeing the frog.

Who’s Singing in Hamilton?

Nine species of frogs and toads can be found in the Hamilton area:

• American Toad (Anaxyrus americanus): the only toad species in the Hamilton area and one of two toad species in Ontario, American Toads are large toads ranging in colour from dark grey to tan and reddish to olive, with dark blotches containing one or two bumps or “warts”. Adult males produce a monotone, high-pitched trill up to 30 seconds long. When many American Toads are singing together, each individual will sing at a slightly different pitch. American Toads begin calling in April, and call most actively through late April and May.
• American Bullfrog (Lithobates catesbeianus): The largest frog in Canada, American Bullfrogs are voracious predators, eating any invertebrate or vertebrate that fits in their mouth (including other frogs). They range from brown to green in colour, sometimes with yellow throats. They can be differentiated from the similarly-coloured Green Frog by the noticeable fold of skin (dorsolateral fold) that runs above and behind their tympana (circular auditory organs behind the eyes). The American Bullfrog call is a deep, resonant sound described with the onomatopoeia “jug-of-rum“. In fact, the French name for this species, Ouarouaron, is also onomatopoeic. American Bullfrogs call later in the year than most species, beginning in May, peaking in mid-June, and continuing into August.
• Green Frog (Lithobates clamitans): Green Frogs are another large frog species, and are closely related to Bullfrogs. They also range in colour frog brown to green, usually with a mottled cream-coloured belly. They can be distinguished from Bullfrogs based on the lack of a fold of skin above and behind their tympana, and the presence of dark, dorsolateral folds, which are folds of skin extending along either side of their back from behind their eyes. The Green Frog call sounds like a low banjo string being plucked, and sing later in the year (from early June to early July).
• Northern Leopard Frog (Lithobates pipiens): Another member of the Lithobates genus, Northern Leopard Frogs grow up to 11 centimetres in length. They range from green to brown in colour, typically with dark oval spots across their body as well as light-coloured dorsolateral folds. Northern Leopard Frogs appear very similar to Pickerel Frogs, but can be distinguished by the random distribution of oval coloured spots along their back, as opposed to rectangular blotches in rows along the backs of Pickerel Frogs. The dorsolateral folds on Leopard Frogs are also more prominent and lighter in colour than on Pickerel Frogs. Northern Leopard Frogs have complex mating calls, ranging from low rattles to croaks and grunts.
• Pickerel Frog (Lithobates palustris): Pickerel Frogs are a medium-sized frog, growing up to 8 centimetres in length. They are generally brown or tan, but may be grey, or drab green as well. They also have prominent dark rectangular spots along their backs, and dark bands on their back legs. These frogs also have distinctive yellow-orange thighs. Their mating call is a low rattle similar to Northern Leopard Frogs, but less complex.
• Wood Frog (Lithobates sylvaticus): Wood Frogs are the smallest member of the Lithobates genus in the Hamilton Area, only growing up to 6 centimetres in length. These frogs range from copper-red to dark brown, but are most easily identified by the dark mask around their eyes and the white stripe right below it on their upper lip. Wood Frogs are some of the earliest frog species to begin breeding in spring, to the point where their eggs are at risk of mortality due to refreezing when laid in shallow ponds. This species is well-known for its ability to survive freezing temperatures during overwintering by increasing their blood glucose level, which acts as an antifreeze. The mating call of Wood Frogs sounds like a repeated chuckle or quack.
• Grey Treefrog (Hyla versicolor): Grey Treefrogs are another small species, growing up to 6 centimetres in length. Grey Treefrogs are able to change the colour of their skin from light and dark grey to green to better blend in with their habitat. They also often have dark blotches, and they have distinct yellow-orange thighs. Being treefrogs, they also have large toe pads that assist them in climbing. Their mating call is a short, high-pitched trill.
• Spring Peeper (Pseudacris crucifer): Spring Peepers are among the smallest frog species in the Hamilton area, growing up to four centimetres. The range in colour from brown to tan, and sometimes appearing grey or orange. They are also distinguished from other species by the distinct X-shape mark across their back, which their latin species name (crucifer) comes from. Spring Peepers are early callers, beginning in April and usually ending by the end of May. Male Spring Peepers are also sometimes heard calling when the temperature decreases in the fall to around the same temperature as their springtime breeding season. The call of the Spring Peeper is, as its name suggests, a high-pitched, loud “peep” that is repeated at intervals of a few seconds.
• Western Chorus Frog (Pseudacris triseriata): Western Chorus Frogs are the smallest frog species in the Hamilton area, only growing to around 3 centimetres in length. Their colours range from brown to grey, and they typically have three darker stripes or blotches along their back. Similarly to Spring Peepers, they call most actively from mid-April until the end of May, but sometimes are heard calling in the fall as well. Their call is a high-pitched trill that has been likened to the sound produced by running your finger across the teeth of a comb.

Take a look at the video below to hear these frog calls in action, as well as the time of year in which each species is calling. Note that this video includes the call for Boreal Chorus Frog (a species not found in the Hamilton area) instead of Western Chorus Frog. However, both species have very similar calls that are difficult to distinguish.

(Information derived from the Ontario Reptile and Amphibian Atlas by Ontario Nature)