Wood Frog

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Photo by: Jerry Mercier

Species: Wood Frog

Scientific name:Rana sylvatica

Status: common

Description: Wood frogs are very distinctive looking; no other frog in Ontario resembles this frog. They are smaller than most other frogs, usually brown in colour, although some individuals have reddish/copper tinge. Their most distinctive feature is the dark brown bar behind their eye, and the thin dark link that runs from their nostril to their eye. In contrast, they have a white upper lip. This frog has dark brown folds along the skin on their back (dorsal folds), and the sides of their bodies commonly have spots. Their hind legs often have dark bands that are clearly visible. Their underbelly is much lighter, typically a white colour, and their toes are not fully webbed.

Habitat: Being an amphibian, this frog needs water. They are commonly found in moist woodlands, and forests. They will often travel across open areas on rainy nights and can be found in forests where bodies of water exist.    

Breeding: Wood frogs are the first frog species to come out of hibernation, and are therefore the earliest breeders. They will commonly be heard calling when ice is still on ponds in the spring. Wood frogs will congregate (come together) at ponds in spring. The ponds they use will be found in woodlands, and may even be ephemeral (temporary ponds). Eggs are laid in large masses, with up to 2000 eggs, which will be attached to vegetation in the pond. The breeding season is short and once breeding is done, adults will live the remainder of the summer on the forest floor. Tadpoles (larval period) will transform into frogs after 2 months. They need to grow quickly and transform before their ephemeral pond dries up. The young frogs will then travel long distances over land to find their own homes.

Diet: Adult wood frogs eat insects, and consume (eat) a lot of mosquitoes. Wood frog tadpoles feed on plant detritus (organic material). 

Threats to species: Wood frogs are a common prey species to a number of animals include most mesocarnivores (medium sized mammals), and birds (song and raptors). Frogs may also be hit by humans if they are traveling on roads on rainy nights (so be careful). Climate change may also impact these frogs as their breeding ponds may dry up before tadpoles are able to transform. Frogs are also susceptible to disease (e.g., Ranavirus, chytrid fungus) and are negatively impacted by toxins in the environment (e.g., farm runoff, pesticides).

Threat to humans: Frogs are no threat to humans. If you see them, check them out, help them when necessary, but do not pick up multiple frogs without cleaning your hands between handling. Scientists aren’t 100% sure how diseases spread in frogs, and humans may be a vector for spread when they handle frogs.

Fun facts:

Wood frogs are freeze tolerant, their blood and tissues can tolerate freezing. Due to this cool ability, they can survive many freeze thaws which allows them to be the first frogs at breeding ponds.

Sources:

Frog watch: http://www.naturewatch.ca/english/frogwatch/species_details.asp?species=23

More information on their ability to tolerate freezing-check out wikipedia (usually I do not consider it a great source, but its a great starting place): http://en.wikipedia.org/wiki/Wood_frog

MacCulloch, R.D. 2002. The ROM field guide to amphibians and reptiles of Ontario.

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