Gray Treefrogs: chameleons of Ontario forests

Jun 01, 2012

by Steve Blight

Photo: Gray Treefrog, gray colouration on a mossy background by Lorraine Julien

Sooner or later, most people that spend time in eastern Ontario forests meet up with a Gray Treefrog. This remarkable little frog shows up in some odd places – stuck to windows at night or even inside a water pump, where the other writer of Outdoors in the Land O’ Lakes, Lorraine Julien, took the picture accompanying this column. Apparently one summer this fellow liked to reside in her neighbour’s hand pump and after several pumps the water would come flushing out along with the frog. He seemed to find this place to his liking because he returned to the pump all summer. I once found a Gray Treefrog in a little hole between two fascia boards at the very peak of our cottage. I only found him because I was doing some painting and I accidently gave him a little dash of white paint. I’m not sure he liked that very much.

Why remarkable? First, this 3-6 cm (1-2.5 inch) lumpy-looking frog has a considerable ability to change colour, varying from light gray to brown all the way to a pale lime green. The change from one colour to another may take an hour or so and may be influenced by temperature, humidity and background colour. In all colour phases there may be one or more dark blotches, sometimes outlined in black, visible on the frog’s back. The undersides of the hind legs and groin of virtually all Grey Treefrogs are coloured orange or bright yellow.

Second, it hibernates on land. Most frog species pass the cold months under water, but this fellow hibernates on land under logs, rocks, leaf litter or even in hollow trees. In early April one year I was searching for a stone for a project around our cottage and when I pulled up a rock, there was a Gray Treefrog. The ground was totally frozen, and my froggy friend was curled up in a little hollow under the rock. I quickly replaced the rock and hoped I hadn’t interrupted his sleep too badly. Gray Treefrogs withstand winter temperatures by producing large amounts of glycerol in their blood and body tissues, which acts as a natural antifreeze to prevent ice from forming in body cells.

Third, it can live a long time. Their potential lifespan is unknown, but captive specimens have survived for over seven years. Each Gray Treefrog starts off life as one of a small cluster of eggs deposited by females in temporary ponds, swamps and the shallow edges of permanent bodies of water. The tadpole hatches in three to seven days where it feeds primarily on algae, and metamorphoses into a tiny green “froglet” in about six to eight weeks. Gray Treefrogs reach maturity after their second winter.

On warm nights in May through early June, many males often call at the same time, creating an unmistakable breeding chorus. The calls are loud, musical trills lasting one half to three seconds that individually could be mistaken for a bird call. Adults are found in deciduous or mixed forests, and are largely nocturnal. They forage for insects in trees and shrubs using their large toe pads to help them climb and move through the branches. Their toe pads produce mucus which allows them to climb up windows to feed on moths and other insects attracted to the light.

Watch for this frog around your home or cottage – and if you see one with a streak of white paint on it, say hi for me!

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.