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Canadian Amphibian and Reptile Conservation Network - Réseau Canadien de 
Conservation des Amphibiens et des Reptiles

Spea bombifrons

formerly Scaphiopus bombifrons

Plains Spadefoot / Crapaud des Plaines


Plains Spadefoot

Description
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 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 is 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.