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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Green Frog
Lithobates clamitans
Family: Ranidae
Until recently, the Green Frog was in the genus Rana, but it is now in the genus Lithobates.
COSEWIC status:- Not Assessed
- No Status
- Least Concern
Description
The Green Frog is a large frog that can attain a body length of up to 11 cm. Individuals are green, olive or brown in colour, and often have dark spots or mottling on the back and a bright green upper lip. The belly is white with darker lines or spots and occasionally has a yellow tinge. The dorsolateral folds (folds of skin running down each side of the back) are prominent and extend halfway down the body. The hind legs have dark crossbands. Males have a bright yellow throat and have tympanum (eardrums) that are noticeably larger than the eyes, while females’ tympanum are about the same size as the eyes. Larvae (tadpoles) have long tails with a large fin and lack front legs (newly hatched tadpoles are legless). They are olive green with dark markings and have green tails that are mottled with brown and a cream-coloured belly. The larvae usually reach lengths of 8–10 cm in length before metamorphosis. The call of Green Frog sounds like a loose banjo string and can be heard singly or as a series of notes.
Similar Species
The Green Frog may be confused with the American Bullfrog and the Mink Frog. The Bullfrog lacks dorsolateral folds. Mink Frog has spots or blotches on the hind legs rather than crossbands and webbing on the Mink Frog’s hind feet extends to the end of the 5th toe and the last digit of the longest (4th) toe, whereas the webbing on the Green Frog’s hind feet is not that extensive.
Distribution
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The Green Frog occurs in eastern Manitoba, Ontario, Quebec, New Brunswick, Prince Edward Island, and Nova Scotia, and it has been introduced in Newfoundland. The Green Frog is also found throughout the eastern In the United States to Minnesota in the north and eastern Texas in the south.
Habitat
Green Frogs can be found in most aquatic habitats, ranging from large lakes and rivers to small creeks and ponds, but they require permanent bodies of water for breeding and hibernation. Juveniles often use temporary bodies of water during the summer and can be found in almost any pool or puddle, including potholes on roads. In wetlands that also contain American Bullfrogs, Green Frogs will tend to use different parts of the wetland than the Bullfrog, usually areas closer to shore and with more vegetation, to avoid predation by the larger frog. Green Frogs hibernate underwater by burying into the mud at the bottom of the water body.
Biology
In Canada, Green Frogs hibernate during the winter and are active from April or early May until September or October, depending on latitude. Male Green Frogs call to attract females during the breeding season, which occurs over a prolonged period from June to August. During breeding, the male grasps the female (amplexus) and fertilization occurs externally in aquatic habitats as the female lays eggs. The female lays 1000–5000 eggs as a large surface film that is up to 30 cm in diameter. The egg mass is deposited among emergent or floating vegetation in water less than 50 cm deep. The eggs are black and are surrounded by two clear jelly envelopes. The eggs hatch in less than a week and larvae will overwinter once or possibly twice before transforming into frogs. Green Frogs reach maturity 1–2 years after metamorphosis and can live for 4–5 years following metamorphosis. Green Frogs are active during the day and night and they forage in aquatic and terrestrial habitats for small invertebrates such as terrestrial and aquatic beetles, moths, slugs, snails, spiders, flies and other insects. Green Frogs may disperse over 1 km from their hibernation site. Male Green Frogs are territorial and will aggressively challenge intruders during the breeding season.
Threats
Green Frogs are one of the most widespread frogs in eastern Canada and they can tolerate habitat disturbance better than many other frog species, although the loss of wetland habitat has been extensive in southern Canada where much of the landscape has been converted to intensive agriculture and urban areas. Large numbers of Green Frogs are killed on roads each year where roads are in close proximity to this species’ aquatic habitat, and high levels of road mortality can cause long-term population declines. Pollution, such as herbicides, agricultural effluent and road salt, can be detrimental to frog populations by causing direct mortality as well as developmental deformities. 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