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Great Basin Spadefoot Toad


The Spadefoot Toad is the only confirmed amphibian species on the INL Site. They grow to about 2.5 inches in length and are usually gray or olive. Spadefoots have a glandular hump between the eyes. Their eyes are large and have vertical pupils like a cat. They get their name from a hard, black, keratinized spade on the first toe of each hind foot, used to dig a burrow, where they spend long periods during cold and dry weather. Spadefoot toads back into their burrow by moving their feet with spades in a circular motion.

Great Basin spadefoots may smell like peanuts when handled. Adults are able to produce skin secretions that cause allergic reactions in some humans, including a burning sensation if the secretion gets in the eyes or nose.

Great Basin Spadefoot toads have adapted to life in dry habitats. Though their range covers most of the western United States, Idaho populations are located primarily in southern Idaho, throughout the desert/ sagebrush regions. To cope with this lack of water, they burrow underground and remain dormant through dry or cold periods. The toad is able to absorb water from the surrounding soil; even as the soil becomes increasingly dry in spring and early summer months. Increased concentrations of urea in the toad's body allow it to continue to suck water out of the soil through osmosis. They can lose up to 48 percent of their body moisture without ill effect.



Spadefoot Toad



Spadefoot Toad Toadlet

When the spring melt and rains arrive, the Great Basin Spadefoot is able to emerge from its burrow. Great Basin spadefoots emerge and begin breeding sporadically from April through July, often after spring or summer rains. Females deposit 300-1,000 black eggs in grapelike clusters of 20-40 eggs in ephemeral ponds. The clusters are attached to vegetation, sticks or pebbles. Spadefoots are considered to be "explosive breeders" because all breeding is done within 1-3 days. The eggs hatch in 2-3 days, depending on water conditions. Tadpole development typically takes as little as 2 weeks if high temperatures and pool drying threatens to strand developing larvae. In Idaho the development of juvenile spadefoots is usually finished by the end of June.

Great Basin spadefoots eat large numbers of ants, other insects, arachnids, and snails. The tadpoles are primarily omnivorous, eating anything that is available.

When drying pools and high temperatures shrink the available water in their habitat, spadefoots dig into the ground and remain dormant until warm weather and rain return. Spadefoots estivate (enter a state of torpor during summer dryness) and hibernate (spend the winter sleeping) in a burrow for up to eight months of the year. During dry weather and droughts, they may not be seen until heavy rains come--which could be up to 10 years apart.


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