What Is It Wednesday: Gray Treefrog

Name: Gray Treefrog (Hyla versicolor)

The Gray Treefrog is a small frog that grows 3-6 cm in length. Although it is called the Gray Treefrog, this species comes in several colours ranging from a light green to a grey or brown. Regardless of colour, its skin has a pebbly or “warty” texture with large dark blotches along its back. Under its eye, you can find a white patch and along its inner thighs and groin is a yellow or orange colour. As you would expect from a treefrog, this species has large suction-cup-like toe disks to help it climb around. They can be found in the southern extents of Canadian provinces ranging from Manitoba to New Brunswick (Figure 1).



Figure 1: Range map for the Gray Treefrog (http://canadianherpetology.ca/species/species_page.html?cname=Gray%20Treefrog).

Like many other frogs, the Gray Treefrog can tolerate temperatures below freezing by increasing the glucose and glycerol levels in its blood. This ensures that the water within their cells won’t freeze as they hibernate in the winter. Particular to this species, though, is the neat capability of changing the darkness or lightness of its skin depending on the temperature and light conditions of its environment. This is described in its Latin name, Hyla versicolor, which means “variable colour”.

Gray Treefrogs largely spend their time in forest canopies located near a permanent waterbody. If it’s not their breeding season, it’s very unlikely you will see this species. When they’re not climbing around or foraging, they’re hiding under leaf litter, rotten logs, tree roots, and in any crevice a tree has to offer. They like to breed in permanent ponds or marshes that have no fish and little-to-no current. You can hear them calling throughout their breeding season from May to July. The Gray Treefrogs call is described as a short, high-pitched trill. Personally, I think it sounds a bit like a raccoon, but take a listen for yourself – Gray Treefrog Call.

Fun Fact: The Gray Treefrog is a tetraploid, meaning it has 4 copies of each chromosome. This is unusual because many frog species are diploids (i.e. they have 2 copies of each chromosome). Despite this trait, the Gray Treefrog has a twin called the Cope's Gray Treefrog, which is a diploid species and does not occur in southern Ontario. Their ranges overlap elsewhere, though, and the only way to tell them apart is by their call – the Cope’s Gray Treefrog has a much faster and higher pitched trill.