Plains spadefoot (Spea bombifrons)

Description
Plains Spadefoot Toad

Size

  • A full-grown adult can attain a total length of 35 to 60 millimetres (1.38 inches to 2.36 inches).

Appearance

  • The plains spadefoot is a plump toad with short limbs and a pronounced bump, underlain with bone, between the eyes.
  • Spadefoots get their name from the "spade"—a wedge-shaped projection (tubercle) on the inner surface of the hind feet used for digging their burrows.
  • These toads resemble both frogs and toads. Their skin is relatively smooth and moist like a frog, but they have some warts on their backs and live on land like a toad.
  • Spadefoots can be distinguished from the true toads of Alberta by:
    • their relatively smooth skin
    • the vertical pupils of their eyes
    • the lack of an enlarged parotoid (poison) gland on the shoulders
  • The colour varies from brown to dull green, usually with four lighter stripes on its back.
  • The small warts on its back are tipped with yellow or orange.
  • When handled, spadefoots emit a sticky secretion.

Voice/call

  • Males call during breeding season to attract females. Their call is short and sounds somewhat like a duck.
Distribution
plains spadefoot distribution in Alberta
  • Within Alberta, the plains spadefoot is limited to the south of the province, primarily in short-grass prairie.
  • Known locations tend to be in natural habitats in areas of sandy soil.
Natural History

Habitat

  • Plains spadefoots inhabit arid and semi-arid regions and survive there by using their "spades" to tunnel backwards and downwards in a corkscrew-like motion into the soil until they find moisture. They have been found as deep as 1 metre (a little over 1 yard) below the surface.

Food

  • Spadefoots eat a variety of invertebrates such as ants and beetles.

When Active

  • While spadefoots are active from spring until fall, they are rarely seen outside of the breeding period.
  • Spadefoots are nocturnal, and are especially active after a rainfall.
Reproduction and Growth
Life Stage Apr May Jun Jul Aug Sep
Breeding Breeding Bar: May 10 to July 7
Eggs Hatch Eggs Hatch Bar: May 15 to July 12
Transformation Transformation Bar: June 10 to August 6

Breeding behavior

  • Once the spring rains begin, breeding will follow quickly.
  • Breeding generally occurs in May (but as late as July) in temporary ponds when spadefoots emerge after heavy rains.
  • Males arrive at the ponds and begin calling to attract females. Their call is short and sounds somewhat like a duck.
  • Once breeding occurs, the eggs are laid in clusters of 10-250 attached to vegetation, a few centimetres below the surface of the water.
  • Within two days, the eggs have hatched. If there is insufficient rain, the spadefoots may not breed at all that year.

Appearance of young

  • Tadpoles can reach a length of up to 68 millimetres (between 2 ½ and 2 ¾ inches).
  • Colour is a light grey or brown on top and lighter underneath.

Growth process

  • Because spadefoots are adapted to temporary water bodies, the developmental process is quite rapid and 21-40 days after hatching, the tadpoles will have transformed into toads.
Conservation and Management

Status

The plains spadefoot is currently classified as May Be at Risk in the current Status of Alberta Wildlife report because its habitat, especially its breeding ponds, is decreasing. See the Status of the Plains Spadefoot in Alberta report at:

Issues

  • Habitat alteration and destruction due to agricultural and petroleum industrial activity has been a limiting factor for species success.

  • Many plains spadefoots are killed on roads as they migrate to breeding ponds.

Current management

  • Amphibian Monitoring in Alberta

    The Great Plains toad is being monitored under the Alberta Volunteer Amphibian Monitoring Program (AVAMP) and the Researching Amphibian Numbers in Alberta (RANA) program.
  • Multiple Species at Risk (MULTISAR) program

    The Great Plains toad is a focal species of the MULTISAR (multiple species at risk) program. Key elements of the program include:

    • Surveying local populations
    • Assessing the ecological status of the habitat
    • Developing management recommendations and habitat enhancement projects
    • Monitoring the species' response over time

    MULTISAR strives to conserve multiple species at risk by working cooperatively with landowners and lease holders to implement voluntary beneficial management practices on native prairie habitat.

Related links
  • Amphibians
    Learn about Alberta's amphibians, their biology and how to identify various species. Also learn about the global decline of amphibian species, and efforts made to monitor and conserve them.

  • Toads
    Find out about the common traits of salamanders, and about the different salamander species found in Alberta.

 

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Posted: Mar 21, 2014