formerly Scaphiopus bombifrons
Plains Spadefoot / Crapaud des Plaines
Spadefoots differ from other frogs and toads by their vertical pupil, relatively smooth
skin, teeth in their upper jaw and absence of
parotoid glands. They also
have a horny, sharp, dark edged knob or
"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.
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.
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
is not found east of British Columbia.
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.
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.
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.
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.
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.