Great Basin Spadefoot

Contents:
 
Links:
Taxon, Status, and Ranks Habitat Photos
General Description State Status Comments
Identification Tips Inventory & Research Needs Key Features
Phenology Threats & Mgmt Concerns
Range References Distribution Map

Taxon, Status, and Rank

Species Spea intermontana     (Cope, 1883)
(= Scaphiopus intermontanus)
Family Pelobatidae
(Spadefoot Toads)
Status None
State Rank S5
Global Rank G5

General Description

This is a small to medium-sized light-colored toad with a plump body, broad waist, short legs, relatively smooth skin and a short, upturned snout (pug-nosed). Adults range in size from 3.8 to 6.3 cm (1.5- 2.5 in) snout-vent length. This family is named for the sharp-edged black horny “spade” present on the inside of the hind feet. The pupil is vertical. A slight swelling, called a boss, is located between the eyes. The dorsal body color is tan, light brown, gray, or olive with indistinct light streaks down the back and sides. The skin is covered with slightly raised brown and/or reddish bumps. Ventral surfaces are light-colored except that in males the throat is dusky colored and nuptial pads are present on the inner most front toes. Newly metamorphosed spadefoots look similar to adults.

The tadpole has a slightly flattened body shape with closely set dorsal eyes, prominent nostrils and a tail fin that starts at the tail-body junction. The overall coloration is dark with lighter dorsolateral bands. The dorsal fin extends just past the end of the tail tip and the end of the tail tapers slightly. The belly has three distinct longitudinal sections and a golden iridescence. The tail musculature is light in color and the tail fins are finely reticulated with light brown. When looking down on the tadpole, the triangular head is distinct from the body, although the outer silhouette is continuous. Tadpoles grow to between 30-70 mm total length before metamorphosis. Newly metamorphosed spadefoots range in size from approximately 10-20 mm snout-vent length.

The eggs are laid in small loose packets of 10-40. The egg packets are approximately 15-20 mm long axis length. The shape of the egg packet is irregular with each egg distinguishable from the others, somewhat like a cluster of grapes. Individual eggs are small with the ovum and gel together measuring less than 5 mm in diameter and each egg can be easily separated from the mass. Egg masses are attached to vegetation or laid unattached directly on the sediments in shallow water.

Voice: The advertisement call is a monotonous, grating, snore-like “wa-wa-wa” audible at great distances. Others describe the call as a low-pitched quacking. The release call is a grating extended single note “waaaaaaaa” accompanied by an arching of the body.

See Photos Page.

Identification Tips

The Great Basin Spadefoot is easily distinguished from all other Washington anurans by the presence of jet black spades on the inside margins of the hind feet. The vertical pupil distinguishes them from all other Washington anurans except the tailed frogs. At night, however, the pupil is round and slow to contract when exposed to bright light. The tadpole is easily distinguished from other tadpoles in Washington by the close-set dorsal eyes, prominent nostrils and the distinct separation between the triangular head and the rest of the body (dorsal view). The egg packets of the Pacific Treefrog are more rounded and symmetric in general appearance (not like a bunch of grapes) and individual eggs cannot be easily separated from the cluster. The Long-toed Salamanders have individual eggs (ovum and gelatinous envelop together when fully expanded) measuring 10 mm or greater in diameter. See Key Features Page.

Phenology

Great Basin Spadefoots start breeding in late March in the Columbia Basin. They are typically “explosive breeders” with all breeding completed in a period of a few days. However, at some sites, males call for weeks or even months. Breeding duration at each site varies with conditions such as water temperature and hydroperiod. Eggs hatch typically in 2-3 days, but development can take longer if water temperatures are cooler. Tadpole development typically takes 1-2 months, but can accelerate with high temperatures if pool drying threatens to strand developing larvae. Spadefoots remain active until late October-early November. Overwintering behavior is unstudied in Washington, but is likely subterranean.

Range

The Great Basin Spadefoot is primarily a species of the Columbia Plateau Ecoregion but the range also extends into the Okanogan Ecoregion. A single report exists of a tadpole found in the Canadian Rockies Ecoregion from Stevens County across the Columbia River from the town of Hudson. Most of the observations in the Okanogan Ecoregion are from the Columbia, Methow, and Okanogan river valleys. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

Great Basin Spadefoots occur primarily in shrub-steppe. A variety of aquatic habitats are used for breeding including slow flowing springs, seasonal pools, irrigation ditches and ponds. Transformed spadefoots are nocturnal and completely terrestrial, only returning to water for breeding. Spadefoots are adapted to survive in arid climates by spending long periods of time buried under ground. They are able to quickly bury themselves in loose soils by using their hind legs in a circular motion to back into the soil. They can remain buried for months at a time and can tolerate high levels of water loss. Activity is reported to be primarily associated with rains and periods of high humidity, however, in many areas of the Columbia Basin, it is common to find individuals on roads at night without precipitation.

State Status Comments

The Great Basin Spadefoot lacks special state or federal status. They occur throughout the Columbia Basin and are locally common in many areas. No declines have been documented in Washington. Great Basin Spadefoots apparently can tolerate some habitat alteration, often persisting in irrigated agricultural lands. It is possible that they have actually increased in abundance due to the prevalence of breeding sites provided in some areas by irrigation water, but no systematic surveys have been conducted to document such patterns.

Inventory and Research Needs

As the distribution map indicates, many areas of the Columbia Basin exist where no Great Basin Spadefoots have been recorded in the Washington Department of Fish and Wildlife herp database. The last records from Spokane, Garfield and Asotin counties were in 1937, 1958 and 1947 respectively. Observation of Great Basin Spadefoots found in these counties, or areas without observation records in the last 20 years, should be submitted to the WDFW reptile and amphibian database by contacting Lori Salzer at salzeljs@dfw.wa.gov.

Threats and Management Concerns

No obvious threats exist at this time, but lack of systematic documentation at sites where they were historical present makes interpretation difficult. Considerable conversion of shrub-steppe, that contained seasonal aquatic habitats historically, provides some justification for refining the basis of existing information.

References

Brown (1989), Corkran and Thoms (1996), Hall (1993, 1998), Hallock (1998a, b, c, 1999), Nussbaum et al. (1983), Stebbins (2003),
Habitat Atlas for Species at Risk (http://wlapwww.gov.bc.ca/sir/fwh/wld/atlas/)


Hallock, L.A. and McAllister, K.R. 2005. Great Basin Spadefoot. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/

Last updated: February 2005


Back to top