Description
The Spotted Frog is a large brown true frog with ill defined
spots which may have light centres. It has dorsolateral
ridges and a dark mask with a light stripe on the upper jaw. Its toes
are fully webbed and the eyes are slightly upturned. The tympanum
is prominent. The underside may be yellow, orange or red with dark mottling
on the throat. Maximum adult size is 10 cm. The two species of Spotted
Frogs are very similar and very closely related. It has only recently be
recognized that they are two different species. The Columbia Spotted Frog
differs from the Oregon Spotted Frog in having a larger head. In Canada,
Columbia Spotted Frogs do not have mottling at the throat although
they do in the United States.
Call
The call is a series of short, rapid grunts which build in intensity.
The entire call may last up to ten seconds. It is not known if the call
differs between the two species.
Confusing Species
The Spotted Frogs may be confused with Red-legged
Frogs which differ in having incomplete webbing on the toes and
not having upturned eyes. Red-legged Frogs are always yellow beneath with red wash on the underside of the legs and the belly. Leopard Frogs have much more distinct dark spots with light rings around them. The other true frogs found within its range do not have spots.
Distribution
In Canada, the Columbia Spotted Frog is found in mountainous
parts of western Alberta and eastern British Columbia as far north as Carcross
in Yukon Territory. The range extends south into the northwestern United
States.
Habitat
Spotted Frogs are found in permanent water in alpine and subalpine
areas with mixed coniferous or subalpine forests.
Reproduction
Breeding occurs early in spring and egg masses are laid communally
with each consisting of 700-1,500 eggs. They hatch in about four days.
Larvae may transform by the end of summer or overwinter as tadpoles and
transform the following year. They may take up to six years to reach maturity.
Natural history
Spotted Frogs are primarily aquatic and when frightened will
swim to the bottom and remain still. Differences in natural history between
the two species have not been explored.
Conservation Concerns
The Columbia Spotted Frog has declined in Alberta as a result
of urbanization. There is no evidence of decline in British Columbia.
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