Boreal Chorus Frog
Last Review/Updated: May 30, 2002
Pseudacris triseriata
Description
Alberta's smallest amphibian, the boreal chorus frog grows to only 20-40 mm in length. It is also known as the striped chorus frog because of the three dark, sometimes broken, stripes on its back. There is also a stripe through the eye and along the side of the frog. The wood frog also has a stripe through the eye, but it is larger and has prominent dorsolateral folds (ridges) on its back.
The background colour of the chorus frog varies from grey to brown to green, while the belly is generally yellowy-white to light green. The skin is somewhat granular in texture. In contrast to true frogs, the boreal chorus frog lacks dorsolateral folds and has little webbing between its toes on the hind feet.
Natural History
The boreal chorus frog is active from spring until fall. It inhabits sloughs, woodlands, and even open meadows if there is sufficient vegetation to provide cover and moisture. It eats a variety of invertebrates including snails and insects. Despite being a member of the tree frog family, the boreal chorus frog is a poor climber and is rarely found higher than the branches of a low shrub. The boreal chorus frog is currently on the Green List in the Status of Alberta Wildlife and is not considered to be at risk. Populations are healthy and widespread.
Breeding
Breeding begins as soon as most of the snow has melted. This breeding can be as early as April in some parts of the province. Males congregate in small ponds or temporary pools and begin calling. The calling can occur during both the night and day. The call is similar to the sound produced by running your fingernail along the teeth of a comb. The eggs are laid in small masses of jelly attached to sticks or other vegetation in shallow water. The number of eggs laid is highly variable, from 150 to 1500. Each egg is about 1 mm in diameter and it will hatch in 10-14 days.
Larvae
The tadpoles are dark with a silvery underside flecked with gold. They are quite small when hatched (4-7 mm) but grow to about 30 mm before transforming into juvenile frogs in about two months time. The newly transformed frogs are quite tiny, only 7-12 mm long after they have absorbed their tails. Nonetheless, they will reach maturity and breed the next summer except in the northern half of the province, where they generally do not breed until their third summer.
DistributionThe boreal chorus frog has the widest distribution of any amphibian in the province. Historically, it was found virtually everywhere in Alberta except for alpine environments. Presently it is excluded from areas where pesticides are heavily used. Outside Alberta it is found all across the prairies and into the Northwest Territories. MonitoringBoreal chorus frogs are at their highest densities during the breeding season. In the spring, adults will congregate at breeding ponds and begin calling. |
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