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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Gray Treefrog
Hyla versicolor
Family: Hylidae
COSEWIC status:- Not Assessed
- No Status
- Least Concern
Description
The Gray Treefrog is a small to medium-sized frog that can grow to 6 cm in body length, and males are typically smaller than females. Individuals are brown, grey or green and typically have dark blotches, sometimes with a distinct dark outline, on the back. Individuals can change between dark and light colouration based on temperature and light conditions. The belly is white but breeding males have a black throat, and the groin and inner thighs are bright yellow. Gray Treefrogs also have bumpy skin, a dark-edged white spot under the eye, dark crossbands on the hind legs, and distinct toe pads. Larvae (tadpoles) have long tails with a large broad fin and lack front legs (newly hatched tadpoles are legless). Larvae are brown to olive-green with varying dark and gold flecks on the body and tail. Tail fins are typically clear, but may develop red colouration with dark margins and blotches when predators are present. The larvae may reach lengths of 4.5 cm before metamorphosis. The Gray Treefrog’s call is a short, slow trill.
Similar Species
Gray Treefrogs may be confused Cope’s Gray Treefrog, Spring Peepers and Chorus Frogs. Cope’s Gray Treefrog has 2 sets of chromosomes (diploid) while the Gray Treefrog has 4 sets of chromosomes (tetraploid). Despite this genetic difference, the two species are identical in appearance and can only be distinguished in the field by the call; the call of Cope's Gray Treefrog is a faster, higher pitched trill than the Gray Treefrog. The Spring Peeper and Chorus Frog are much smaller than Gray Treefrogs as adults, have less pronounced toe pads, and lack the white spot under the eye.
Distribution
Click for larger image
The Gray Treefrog occurs throughout eastern Canada in eastern Saskatchewan, southern Manitoba, northwestern Ontario, southern Ontario east of Lake Superior, southwestern Quebec and southern New Brunswick. This species also occurs throughout the northeastern United States west to North Dakota and in a narrow band extending south to Eastern Texas, but are absent from North Carolina west to Mississippi and south to Florida.
Habitat
Gray Treefrogs inhabit a variety of forest habitats, and adults spend the majority of their time in the forest canopy. Individuals breed in permanent or ephemeral wetlands that are in open-canopy areas but within close proximity to forest. Breeding sites are typically fish-free, and the introduction of predatory fish can result in the loss of Gray Treefrogs from the site. Individuals hibernate by burying themselves in the forest floor.
Biology
n Canada, Gray Treefrogs hibernate during the winter and are typically active from April until late September or early October. Males call to attract females during the breeding season, which occurs over a prolonged period from May to July. During breeding, the male grasps the female (amplexus) and fertilization occurs externally in aquatic habitats as the female lays eggs. The female attaches 1,000–2,600 eggs singly or as small clusters of 10–40 eggs to submerged vegetation near the water’s surface. The eggs are brown and are surrounded by a clear jelly envelope. The eggs develop rapidly and hatch in 1–3 weeks at northern latitudes, depending on water temperature. The tadpoles transform into frogs in 1–2 months and individuals reach sexual maturity in 2 years. Gray Treefrogs can live up to 8 years, but most individuals probably do not live more than 5 years in the wild. Gray Treefrogs are able to survive sub-freezing temperatures during hibernation by increasing the levels of glucose and glycerol in their blood, which acts as a “cryoprotectant” and prevents water from freezing inside the cells. Individuals are active during the day and night and they forage on the forest floor and in the canopy for a wide variety of insects, spiders and other small invertebrates.
Threats
The conversion of wetland and forest to urban and agricultural land uses is a significant threat to this species throughout the southern portion of its Canadian range. Forestry operations that result in large-scale removal of forest cover (e.g. clear-cutting) may also result in the destruction of this species’ habitat. Pollution, such as herbicides, agricultural effluent and road salt, can be detrimental to frog populations by causing direct mortality as well as developmental deformities. Road mortality is less of an issue for this species than many other Canadian frogs, but it can be a significant threat when roads bisect the species’ habitat. Pathogens such as chytrid fungus and Ranavirus can cause mass mortality of frog populations. Climate change may also pose future threats to Canada’s frog populations.