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The gray treefrog (Dryophytes versicolor, synonym Hyla versicolor) is a small to medium-sized treefrog native to Central and Northeastern North America. In Canada, they are found in New Brunswick, Quebec, Ontario, Manitoba and a small part of Eastern Saskatchewan. Gray treefrogs are well camouflaged; the scientific name versicolor means “changing colour” and refers to the frog’s ability to make their skin lighter or darker. Gray treefrogs have one of the loudest calls of any North American frog.
Description
The gray treefrog is a small to medium-sized frog that can reach 6 cm in length. Females are generally larger than males. Gray treefrogs can be gray, green or brown. They have large, dark blotches on their back and light speckles in a pattern that resembles lichen growing on tree bark. The undersides of their thighs are bright yellow-orange and are usually hidden.
Like many other species of treefrog, gray treefrogs can change their colour rapidly. Like all treefrogs, gray treefrogs have large toepads that they use to climb trees.
The tadpoles of gray treefrogs have a brown or olive body with black and gold speckles. Their belly is lighter with gold flecks and their eyes are bright gold or bronze. They may grow to be as long as 4 cm. The tail fin is transparent unless predators are present in the same pond. In that case, the tail fin grows to become bright red-orange with a dark margin which appears as the tadpole nears metamorphosis.
Gray Treefrog vs. Cope’s Gray Treefrog
Gray treefrogs cannot be visually distinguished from Cope’s gray treefrog. Gray treefrogs are a “tetraploid form” of Cope’s gray treefrog (Dryophytes chrysoscelis). This means that the main trait that differentiates the gray treefrog from the Cope’s gray treefrog is that the former has four sets of chromosomes rather than the usual two. These two species are known as the “gray treefrog complex.” Despite their similarities, they are still considered separate species because they do not generally reproduce with one another. The best way to differentiate these two species is to compare their geographical ranges and, where their ranges overlap, through genetic testing. Within Canada, the Cope’s gray treefrog can only be found in Southern Manitoba and a small area of Southwestern Ontario. They also have slightly different calls.
Distribution and Habitat
Within Canada, the gray treefrog is found in New Brunswick, Southern Quebec, Ontario, Manitoba and a small part of Eastern Saskatchewan. In the United States, the gray treefrog can be found throughout the Northeastern states, as well as further south in states including Missouri, Oklahoma, Arkansas and Texas.
Gray treefrogs spend most of their time in shrubs and trees, where they can be found very high up in the canopy. They generally prefer to live in woodlands near a breeding site but can sometimes be found in human-made environments, such as orchards and suburban areas. To breed, gray treefrogs seek out sources of water in which to lay their eggs, such as ponds, wetlands and ditches. They can be difficult to see, both because of their excellent camouflage and because they tend to hide in such places as tree holes and under bark. They can sometimes be seen on the sides of buildings or on windows.
Gray treefrogs overwinter under leaf litter and snow cover. They are tolerant of freezing temperatures. They can survive having more than 40 per cent of the fluids in their body freeze without ill effect. They achieve this through the use of the cryoprotectants glucose and glycerol. These substances prevent water from freezing within their cells, which protects them from significant damage.
Reproduction
Gray treefrogs breed from late spring to early summer. Males gather around a breeding site, calling from trees and shrubs to attract females. The gray treefrog’s call is a short trill. It is one of the loudest frog calls heard in North America.
Females lay up to 2,600 eggs in a year. They may be laid individually or in small groups of 4–40 eggs. Like most frogs, the eggs are fertilized by the male externally, as they are being laid. The eggs are gray-brown and enclosed in a single jelly envelope. Including this envelope, each egg is approximately 0.5 cm in diameter.
The eggs typically hatch after 2–7 days. The tadpoles metamorphose into frogs 40–60 days after hatching. They reach sexual maturity after 2 years and, while their lifespan in the wild is unknown, they can live 7 years in captivity.
Diet and Predation
Gray treefrogs eat a wide variety of insects. Beetles and ants make up the majority of their diet, but they are also known to eat other invertebrates such as crickets, moths, spiders and cockroaches.
Adult gray treefrogs are prey to a variety of animals such as birds, snakes, bullfrogs and raccoons. Their best defence is camouflage, which can make them very difficult to spot. Tadpoles also face a variety of predators, including insects, fish and salamander larvae. The colourful tail fin they develop in the presence of predators seems to deflect attacks away from the body, helping the tadpoles escape unharmed.
Conservation and threats
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has not assessed the gray treefrog. Internationally, it has been listed as “least concern” by the International Union for Conservation of Nature.
The population trends of gray treefrogs have not been studied in detail, but they are believed to be abundant and widespread. However, gray treefrogs are still vulnerable to extreme habitat loss, as they rely on forest habitats and breeding ponds They are negatively affected by human activities such as clear-cutting and urbanization. Roads, when built near breeding ponds, can often cause high local mortality as frogs travel to and from the water body.
