By Terri-Lee Reid
As spring comes alive with the sound of frogs there is one group in particular, the treefrogs, that continue to fascinate us with their small size and unique toe-pads.
With seven species of treefrogs in Canada, they can be found across most of the country. However, despite their general distribution many of us may never see a treefrog due to their small size and their ability to camouflage with their background. Treefrogs are typically grey, green or brown with many species able to undergo changes in their colour depth. While a few species are commonly found close to the ground, most live in trees and shrubs. The sticky disks on their toes help them adhere to bark, branches and twigs where many forage for insects.
Treefrogs may be most noticeable in the spring as males begin calling for a mate. Some species, such as the spring peeper and the chorus frogs, are well known for their singing at this time. In Canadian species, females lay their eggs in water either in small masses or as single eggs.
Even though treefrogs are small in size, most Canadian species spend their winters under only leaf litter, rocks, logs or tree bark. They have the ability to create antifreeze, glucose or glycerol, which prevents their organs from freezing in the cold Canadian winters.
Find out which species occur in your area:
Northern Cricket Frog (Acris crepitans)
In Canada, northern cricket frogs are found only on Pelee Island, Ontario. They can be identified by their rough, warty looking skin that is usually brown or grey. A distinguishing feature is a dark “V” mark located between their eyes. This species does not have large toe pads. Adults typically are no larger than 4 cm.
Northern cricket frogs are most commonly found in marshes, quarries and even ditches. They don’t start breeding until the middle of summer and the female may lay as many as 400 eggs that hatch into tadpoles in only three or four days, becoming frogs in five to ten weeks. Insects make up a large part of their diet and they spend their winters under rocks or logs. They are an endangered species.
Western Chorus Frog (Pseudacris triseriata) and Boreal Chorus Frog (Pseudacris maculata)
Western chorus frogs and boreal chorus frogs are very similar in appearance and behaviour although they differ in their Canadian distributions. Western chorus frogs are found only in southern Ontario and southern Quebec whereas boreal chorus frogs are found from Quebec west to British Columbia, the Northwest Territories and slightly into the Yukon Territories.
Reaching a maximum size of only 4 cm, both species have smooth skin and can be grey, green, or brown in colour. Helping to distinguish them from other treefrogs is their dark eye stripe, the white stripe along their top lip and their three dark dorsal stripes. To help distinguish between these two species, the mid-dorsal stripe is typically a solid line in the western chorus frog but tends to be broken in boreal chorus frogs. Boreal chorus frogs also have shorter hind legs than western chorus frogs.
Western and boreal chorus frogs are commonly found in woodland ponds but will breed in almost any pond as long as there are no fish and its at least 10 cm deep. They breed in the spring and females deposit up to 800 eggs in small masses. Eggs quickly hatch into tadpoles, becoming frogs by mid summer.
Their diet consists of insects and other invertebrates. Their winters are spent either below ground or under logs. These species are not as accomplished at climbing as other treefrogs, climbing no higher than a small shrub.
Cope’s Grey Treefrog (Hyla chrysoscelis) and Grey Treefrog (Hyla versicolor)
Cope’s grey treefrog and the grey treefrog are identical in appearance and can only be distinguished from each other by their distribution and their calls. In Canada, Cope’s grey treefrogs are found only in Manitoba and in western Ontario whereas grey treefrogs are found from Manitoba east to New Brunswick.
The cope’s grey treefrog’s call is faster and higher pitched than the grey treefrogs shorter more flutey call.
Both species reach a maximum size of 6 cm, are rough skinned with a background colour of green, grey or brown but have the ability to quickly change shades. Their skin is covered with dark marks that are outlined in an even darker colour. The inside of their thighs is orange and they have large toe disks.
These species are usually found wherever there is a permanent body of water and are usually found high up in trees and shrubs. Breeding doesn’t occur until late in the spring. The female may lay a total of 2000 eggs that are divided into smaller masses and attached to aquatic plants. Within five days the eggs hatch and approximately two months later the tadpoles transform into frogs. Both species feed on insects and other invertebrates. These treefrogs spend their winters under only leaf litter and snow.
Spring Peeper (Pseudacris crucifer)
The spring peeper is the treefrog most are likely familiar with. They have a broad Canadian distribution from Manitoba east to Prince Edward Island. They can range in colour from brown to grey but their distinguishing feature is an “X” shape on their back. They have large toe pads and only reach 3 cm in size.
They are one of the earliest frogs to sing in the spring.
They breed basically wherever there is water but are sensitive to the impacts of urbanization. Females can lay up to 1000 eggs either in masses or as single eggs. The eggs hatch into tadpoles about a week later and after two months they are frogs. Their diet consists of mosquitoes, worms and aphids. They spend their winters under leaves, logs or tree bark.
Pacific Treefrog (Pseudacris regilla)
The Canadian range for this rough-skinned treefrog is limited to British Columbia. Pacific treefrogs are typically green or brown but they do have the ability to change shades quite quickly. Their distinguishing feature is a dark stripe that runs through each eye and they have large sticky toe pads. They can obtain lengths up to 5 cm.
Pacific treefrogs are commonly found close to the ground. By early spring, females have laid masses of up to 50 eggs which transform into frogs after only two months. They feed on worms, flies and beetles. Pacific treefrogs can be heard all year long singing their familiar call.
Amphibians are an essential part of the environment as regulators of insect populations and indicators of environmental health. But frogs are paying the price for our actions as their numbers continue to decline. Pesticides and other contaminants are entering their bodies through their permeable skin and invasive species, such as domestic cats, are also having an impact on their numbers. But you can help the frogs in your area, including treefrogs, by avoiding the use of pesticides, by providing areas of vegetation for shelter and hunting and by building a pond. For more information on how you can help these creatures see our Frogs, Toads & Other Creepy Critters section.