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Upper Midwest Environmental Sciences Center

Farm ponds as critical habitats for native amphibians
A Field Guide to Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa
Field guide contents

Plains Spadefoot Spea bombifrons

Status: Iowa – Locally abundant
Plains Spadefoot
4.0 - 4.8 cm total length

field mapPlains Spadefoots are present in extreme western Iowa. Adults spend most of the year underground and breed explosively (all within a few days or weeks) in small pools after heavy spring rains (even depressions in agricultural fields) and occasionally in more permanent ponds. The eggs and tadpoles develop quickly; eggs hatch in about 20 hours at 30°C (Justus et al. 1977), and a population in Oklahoma required only 13–14 days from egg to metamorphosis (King 1960). The eggs are laid in a cylindrical or elliptical mass of 10–250 eggs that is attached to submerged vegetation. Plains Spadefoot tadpoles have a medial vent, a characteristic they share only with toads in our region. The body is dark brown or bronze in color, and is large and bulbous (broadest just behind the eyes) with mostly clear tail fins. Pigmented "veins" are usually found on the clear fins. The spiracle is found lower on the body than our other frogs (Figure 4c). Tadpoles may also be rapidly developing "carnivorous morphs," with larger heads and mouths than the typical omnivorous forms (Pfennig 1992). A black "spade" will be observable on the hind feet well before metamorphosis.

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Page Last Modified: December 29, 2010