Description
Spadefoots differ from other frogs and toads by their vertical pupil,
relatively smooth skin, teeth in their upper jaw and absence of parotid
glands. They also have a horny, sharp, dark edged knob or tubercle
(the "spade") on the inner surface of the hind foot. The Plains
Spadefoot is a stout bodied animal with a prominent bony hump between the
eyes. The spade is round to wedge shaped. The skin is fairly smooth gray
to brown with overtones of green and small scattered orange bumps. There
may be light stripes on the back. The belly is white. Maximum adult size
is 6 cm.
Call
The call is a series of short, harsh, barks repeated over
and over at about one second intervals. Although similar to the call of
the Wood Frog, the Plains Spadefoot call is
repeated more slowly.
Confusing Species
The Tailed Frog also has vertical pupils
but does not have a tympanum and lives in very different habitat. The Great
Basin Spadefoot looks very similar, however, the hump between the eyes
is glandular rather than bony and the spade is always wedge-shaped. Fortunately
their ranges do not overlap -- the Great Basin Spadefoot it not found east
of British Columbia.
Distribution
The Plains Spadefoot is found, not surprisingly on the Great Plains
of midwestern North America. In, Canada it is found in southernmost Alberta
and Saskatchewan and southwestern Manitoba. It is found as far south as
Texas.
Habitat
The Plains Spadefoot is found in shortgrass prairie with loose, dry
sandy or gravelly soil. They breed in temporary ponds formed by spring
or summer rainstorms.
Reproduction
The time of reproduction is set by the onset of heavy rain which stimulates
the spadefoots to surface and begin calling. From 10 to 250 eggs are laid
and hatched within 48 hours. Tadpoles transform within 21 to 40 days. Development
is often a race against time as their ponds slowly evaporate. Some larger
tadpoles may gain an edge by eating smaller ones. Adults may forgo breeding
for several years if rainfall is insufficient.
Natural history
Plains spadefoots are rarely seen except during breeding. They are nocturnal
and most active after rain when they emerge to feed on insects such as
ants and beetles. During the day they hide underground in burrows made
by tunnelling backwards using their spades. They have been found as deep
as a meter underground. These behaviours help them conserve moisture on
the dry plains. Spadefoots also spend the winter burrowed underground.
Conservation Concerns
There is no evidence of decline in this species
but it is considered rare in Saskatchewan and at risk in Alberta. It is
difficult to detect.
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