Plains Spadefoot - Spea bombifrons
State Rank Reason (see State Rank above)
Recent nocturnal calling surveys conducted after precipitation events on warm evenings have often detected this species east of the Continental Divide. It appears that the previous perception of rarity was due in part to lack of historical survey effort and difficulty detecting the species during much of the year and in most weather conditions. Given these data, the SOC status can no longer be justified and the rank has been increased to S4.
- Details on Status Ranking and Review
ScoreG - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment282,342 square Kilometers from Natural Heritage Program range maps
ScoreE - Relatively Stable (±25% change)
CommentAs the species uses pasture and some agricultural lands, habitat has likely been relatively stable since European arrival
ScoreE - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation
CommentSpecies appears to be stable based on repeated detections at some sites.
ScoreF - Widespread, low-severity threat. Threat is of low severity but affects (or would affect) most or a significant portion of the population or area.
CommentMortality on roads, contamination of breeding sites with agricultural chemicals or fecal matter from cows, irrigated fields functioning as ecological traps
SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.
CommentAny degradation of habitat or decline in population would likely be reversible within a few decades
ScopeModerate - 20-60% of total population or area affected
CommentThreats exist across much of this species range
ImmediacyHigh - Threat is operational (happening now) or imminent (within a year).
ScoreC - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
CommentHigh fecundity, relatively low age of maturity
ScoreC - Moderate. Generalist. Broad-scale or diverse (general) habitat(s) or other abiotic and/or biotic factors are used or required by the species but some key requirements are scarce in the generalized range of the species within the area of interest.
CommentSpecies requires ephemeral waterbodies and specific soil types. Both are found across much of eastern and central Montana
Raw Conservation Status Score
3.5 + 0 (geographic distribution) + 0 (environmental specificity) + 0 (short-term trend) + 0 (threats) = 3.5
Adult Plains Spadefoot are gray or brown with darker mottling on the back and white on the belly. The back may be covered with smallish tubercles tipped in yellow or orange, and often present as a rough hourglass-shaped marking. Some individuals have indistinct longitudinal streaking. In adults the pupils are vertically elongate in bright light; there is a hard lump or "boss" between the eyes, slightly anterior of an imaginary midline connecting the eyes. Prominent parotoid glands posterior to the eyes are absent. A single hard and dark wedge-shaped spade is present on each hind foot. Maximum snout-vent length (SVL) is about 6.0 centimeters. Males have dark patches on the inner 2-3 digits of the forelimbs during breeding, and have an expanded bi-lobed vocal sac. The male breeding call is a brief snore.
Tadpoles may be brown or green to whitish on the back, or mottled gray to dull olive-yellow, sometimes with a bluish iridescence. The belly is an iridescent golden color; the gut coil is not visible through the body wall. The dorsal fin is clear or with sparse yellowish flecking; the anus is at the base of the tail on the midline. The body shape is globular, with the eyes positioned dorsally, and total length is usually up to 7.0 centimeters. The mandibles are frequently cusped; labial tooth rows are 0/0 to 6/6, but most often 3/4 or 4/4. Oral papillae completely encircle the mouth. Eggs are black above and white below, about 1.5 to 1.6 millimeters in diameter and surrounded by two jelly layers, and deposited in elliptical masses of 10 to 250 eggs.
No other adult frog or toad in Montana has a combination of vertical pupils, bony "boss" between the eyes, large black tubercles or spades on the hind feet, and lack of prominent parotoid glands. No other tadpoles have a combination of a normal (not sucker-like) mouth completely surrounded by oral papillae, and a midline anal vent at the base of the tail. No other Montana amphibian has small (less than 4.0 millimeters) pigmented eggs surrounded in two jelly layers that are laid singly or in short linear or globular clusters. The Great Basin Spadefoot (Scaphiopus inermontanus) is known from southeastern Idaho and may occur in southwestern Montana; it has a low and pliable lump between the eyes, while the Plains Spadefoot's lump is high and hard.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
No information specific to Montana Plains Spadefoot is available. Elsewhere adults are known to migrate up to several hundred meters between breeding pools and nonbreeding terrestrial habitats. During breeding, they may move 60 to 150 meters during each night as they leave the breeding ponds and move inland (Hammerson 1999).
Little specific habitat information is available. This species is usually found in areas with soft sandy/gravelly soils near permanent or temporary bodies of water. For much of each year it lives largely inactive in burrows of its own construction or occupies rodent burrows, and enters water only to breed. Following heavy rains, adults have been reported in water up to 30 centimeters deep in flooded wagon wheel ruts, temporary rain pools formed in wide flat-bottom coulees, water tanks, and badland seep ponds, and tadpoles and toadlets have been observed in stock ponds and small ephemeral reservoirs, usually in sagebrush-grassland habitats (Cope 1879, Mosimann and Rabb 1952, Dood 1980, Reichel 1995, Hendricks 1999, Hossack et al. 2003).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Human Land Use
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
Metamorphosed Plains Spadefoot in Colorado eat various small terrestrial arthropods, including spiders, terrestrial amphipods, snails, earthworms, centipedes, and nine orders of insects, especially moths, caterpillars, and ground beetles (Whitaker et al. 1977), and rarely small vertebrates (Hammerson 1999). In the playa wetlands of northwest Texas, carabid beetles were the most common food (Anderson et al. 1999). Larvae eat suspended matter, organic debris, algae, and plant tissue. Large larvae may develop into predatory tadpoles that eat relatively large aquatic invertebrates, such as fairy shrimp and insect larvae, as well as other amphibian larvae, including their own species (Hammerson 1999). Food habits in Montana have not been studied.
Plains Spadefoots are mostly active as adults at dusk and night when air temperatures are between 12 and 26 degrees C. Adults in Alberta, Wyoming, and Colorado may be active anytime during May through August and less frequently later (Baxter and Stone 1985, Russell and Bauer 1993, Klassen 1998, Hammerson 1999), depending on rains and the presence of standing water. In Montana, adults have been observed during May to August (Mosimann and Rabb 1952, Hendricks 1999, Hossack et al. 2003). When conditions are such that adults retreat underground, the spades on the hind feet are used to dig backwards into the soil until pockets of moist soil are encountered, sometimes at depths of almost a meter. Tadpoles may be able to tolerate brief periods of almost total evaporation of their pools (Russell and Bauer 1993).
Predators of adults and juveniles include birds (Swainson's Hawk, Burrowing Owl, Black-crowned Night-Heron), and Western Rattlesnakes; tadpole predators include gartersnakes, the tadpole shrimp (Triops sp.), and cannibal Plains Spadefoot tadpoles (Baxter and Stone 1985, Hammerson 1999). Predators in Montana are not reported. Threatened adults inflate with air and squat with the head bent downward, and often release fluid from the vent if handled; large tadpoles may produce a clicking sound with their mouthparts if removed from water (Hammerson 1999).
Little specific information is available. Adult choruses have been heard from late May through early August. Tadpoles from legless to 4-legged stages have been reported during late June of the same year in Carbon County (Hendricks 1999), and fully transformed juveniles have been found in the same area during a different year in late August (Maxell et al. 2003). Recently transformed juveniles have been reported along the Missouri River in late August (Cope 1879).
Breeding occurs in Colorado after heavy rains of 1.8 centimeters or more at air temperatures greater than 10 degrees C. (Hammerson 1999). Breeding choruses usually last about 2 or 3 days, with adults calling from edges of the pools or while floating; large choruses can be heard from a distance of 3 kilometers or more. Females lay up to 2700 eggs during a single breeding event, often in several egg masses each attached to submerged vegetation or other objects. Adults usually leave the water once breeding and egg-laying are finished, but may remain nearby for several days if rain continues. Rains occurring after the first round of breeding may stimulate more breeding, presumably from individuals that did not breed the first time. Adults probably reach maturity when 2 to 3 years old. Iowa males are mature when 3.1 to 3.8 centimeters snout-vent length (SVL), females when 3.2 to 4.0 centimeters SVL; breeding adults in Colorado are typically 4.0 to 6.0 centimeters SVL (Hammerson 1999).
Eggs hatch in 2 to 3 days. Tadpoles develop rapidly, and complete metamorphosis in about 36 to 40 days (21 to 75 days) in Colorado (Hammerson 1999). In Alberta, time to metamorphosis was a minimum of 21 to 34 days and a maximum of more than 60 days (Klassen 1998). Transforming toadlets emerged from water may still have tails.
No special management needs are currently recognized. However, at permanent and semi-permanent water bodies (reservoirs and stock ponds) where breeding has been observed, portions of the shoreline where emergent vegetation might develop could be fenced to create exclosures that protect breeding adults, eggs and tadpoles from trampling and the removal of emergent cover by livestock; trampled juveniles have been found at some stock ponds (Paul Hendricks, personal observation). Another option would be the creation of ponds designed for use by prairie amphibians as breeding sites, with the perimeter surrounded by fencing to prevent access by livestock. Game fish should not be introduced to any of these ponds.
- Literature Cited AboveLegend: View Online Publication
- Anderson, A. M., D. A. Haukos, and J. T. Anderson. 1999. Diet composition of three anurans from the playa wetlands of northwest Texas. Copeia 1999:515-520.
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- Hossack, B., D. Pilliod, and S. Corn. 2003. Amphibian survey of Medicine Lake National Wildlife Complex: 2001-2002. USGS Northern Rocky Mountain Science Center, Aldo Leopold Wilderness Research Institute, Missoula, Montana. 19 p.
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- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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