Plains Spadefoot - Spea bombifrons
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
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Records associated with a range of dates 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 (high, medium, or low) 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 2001, 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 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 associated as using 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 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.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the 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 assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at firstname.lastname@example.org
or (406) 444-3655.
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. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- 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
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
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 WorldCat Record 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.
- Baxter, G. T. and M. D. Stone. 1985. Amphibians and reptiles of Wyoming. Second edition. Wyoming Game and Fish Department. Cheyenne, WY. 137 p.
- Cope, E. D. 1879. A contribution to the zoology of Montana. American Naturalist 13(7): 432-441.
- Dood, A. R. 1980. Terry Badlands nongame survey and inventory final report. Montana Department of Fish, Wildlife, and Parks and Bureau of Land Management, Helena, MT. 70 pp.
- Hammerson, G. A. 1999. Amphibians and reptiles in Colorado. University Press of Colorado & Colorado Division of Wildlife. Denver, CO. 484 p.
- Hendricks, P. 1999. Amphibian and reptile survey of the Bureau of Land Management Miles City District, Montana. Montana Natural Heritage Program, Helena, MT. 80 p.
- 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.
- Klassen, M.A. 1998. Observations on the breeding and development of the plains spadefoot (Spea bombifrons) in southern Alberta. Canadian Field Naturalist 112(3): 387-392.
- Maxell, B. A., J. K. Werner, P. Hendricks and D. L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Society for Northwestern Vertebrate Biology, Northwest Fauna Number 5. Olympia, WA. 135 p.
- Mosimann, J.E. and G.B. Rabb. 1952. The herpetology of Tiber Reservoir Area, Montana. Copeia(1): 23-27.
- Reichel, J. D. 1995. Preliminary amphibian and reptile survey of the Sioux District of the Custer National Forest: 1994. Montana Natural Heritage Program, Helena, MT. 75 p.
- Russell, A. P. and A. M. Bauer. 1993. The amphibians and reptiles of Alberta. University of Calgary Press. Calgary, Alberta. 264 p.
- Whitaker, J.A., Jr., D. Rubin and J.R. Munsee. 1977. Observations on food habits of four species of spadefoot toads, genus Scaphiopus. Herpetologica 33(4): 468-475.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
- [PRESI] Powder River Eagle Studies Incorporated. 1998a. Big Sky Mine 1997 wildlife monitoring studies. Powder River Eagle Studies Incorporated. Gillete, WY.
- [PRESI] Powder River Eagle Studies Incorporated. 1998b. Spring Creek Mine 1997 wildlife monitoring studies. Powder River Eagle Studies Incorporated. Gillete, WY.
- [VTNWI] VTN Wyoming Incorporated. No Date. Second year's analysis of terrestrial wildlife on proposed mine access and railroad routes in southern Montana and northern Wyoming, March 1979 - February 1980. VTN Wyoming Incorporated. Sheridan, WY. 62 p.
- [WESTECH] Western Technology and Engineering Incorporated. 1998. Wildlife monitoring Absaloka Mine area 1997. Western Technology and Engineering, Inc., Helena, MT.
- Allen, J.A. 1874. Notes on the natural history of portions of Dakota and Montana Territories, being the substance of a report to the Secretary of War on the collections made by the North Pacific Railroad Expedition of 1873, General D.S. Stanley, Commander. Proceedings of the Boston Society of Natural History 17: 33-85. Pages 68-70.
- Atkinson, E.C. and M.L. Atkinson. 2004. Amphibian and reptile survey of the Ashland and Sioux of the Custer National Forest with special emphasis on the Three-Mile Stewardship Area:2002. Marmot's Edge Conservation. 22 p.
- Bauer, Delane, 2002, 2002 Four Seasons Wildlife Study. Savage Mine Report, Richland County, Montana.
- Black, J.H. 1973. Ethoecology of Scaphiopus (Pelobatidae) larvae in temporary pools in central and southwestern Oklahoma. Ph.D. Dissertation, University of Oklahoma. Norman, Oklahoma. 221 pp.
- Black, J.H. 1974b. Larval spadefoot survival. Journal of Herpetology 8(4): 371-373.
- Blair, W.F. 1949. Development of the solitary spadefoot toad in Texas. Copeia 1949(1): 72.
- Blair, W.F. 1955. Differentiation of mating call in spadefoots, genus Scaphiopus. Texas Journal of Science 7: 183-188.
- Blair, W.F. 1956b. The mating call of hybrid toads. Texas Journal of Science 8: 350-355.
- Blair, W.F. 1958b. Mating call in the speciation of anuran amphibians. American Naturalist 92: 27-51.
- Boundy, J. 1992b. Spea bombifrons (Plains spadefoot). Herpetological Review 23(1): 25.
- Bragg, A.N. 1941. Tadpoles of Scaphiopus bombifrons and Scaphiopus hammondii. Waserman Collector 4: 92-94.
- Bragg, A.N. 1944. The spadefoot toads in Oklahoma with a summary of our knowledge of the group. American Naturalist 78: 517-533.
- Bragg, A.N. 1946. Aggregation with cannibalism in tadpoles of Scaphiopus bombifrons with some general remarks on the probably evolutionary significance of such phenomena. Herpetologica 3: 89-96.
- Bragg, A.N. 1948a. Additional instances of social aggregations in tadpoles. Wassmann Collector 7: 65-79.
- Bragg, A.N. 1956. Dimorphism and cannabalism in tadpoles of Scaphiopus bombifrons (Amphibia, Salientia). Southwestern Naturalist 1: 105-108.
- Bragg, A.N. 1962a. Predation on arthropods by spadefoot tadpoles. Herpetologica 18: 144.
- Bragg, A.N. 1962b. Predator-prey relationship in two species of spadefoot tadpoles with notes on some features of their behavior. Wasmann Journal of Biology 20: 81-97.
- Bragg, A.N. 1964. Further study of predation and cannibalism in spadefoot tadpoles. Herpetologica 20(1): 17-24.
- Bragg, A.N. 1965. Gnomes of the Night: The Spadefoot toads. University of Pennsylvania Press, Philadelphia.
- Bragg, A.N. 1966. Longevity of the tadpole stage in the plains spadefoot (Amphibia: Salientia). Wasmann Journal of Biology 24: 71-73.
- Bragg, A.N. and O. King. 1960. Aggregational and associated behavior in tadpoles of the Plains spadefoot. Wasmann Journal of Biology 18:273-289.
- Bragg, A.N. and W.N. Bragg. 1958. Parasitism of Spadefoot tadpoles by Saprolegnia. Herpetologica 14: 34.
- Bragg, A.N. and W.N. Bragg. 1958b. Variations in the mouth parts in tadpoles of Scaphiopus (Spea) bombifrons Cope (Amphibia: Salientia). Southwestern Naturalist 3: 55-69.
- Bragg. A.N. 1945. The spadefoot toads in Oklahoma with a summary of our knowledge of the group. II. American Naturalist 79: 52-72.
- Brown, H.A. 1976. The status of California and Arizona populations of the western spadefoot toads (Genus Scaphiopus). Contributions of Science of the Natural History Museum of Los Angeles Co. 286 pp.
- Brunson, R.B. 1955. Check list of the amphibians and reptiles of Montana. Proceedings of the Montana Academy of Sciences 15: 27-29.
- Buchholz, D. and T.B. Hayes. 1996. Comparative larval biology in spadefoot toads. American Zoologist 36(5):97.
- Buchholz, D. and T.B. Hayes. 2000. Evolution of diversity in anuran tadpoles: accelerated metamorphosis in spadefoot toads. American Zoologist 40(6):957.
- Buchholz, D.R. and T.B. Hayes. 2002. Evolutionary patterns of diversity in spadefoot toad metamorphosis (Anura: Pelobatidae). Copeia 1:180-189.
- Burton, S.R., D.A. Patla, and C.R. Peterson. 2002. Amphibians of Red Rock Lakes National Wildlife Refuge: occurrence, distribution, relative abundance, and habitat associations. Herpetology Laboratory, Department of Biological Sciences, Idaho State University, Pocatello, ID. 66 p.
- Cannatella, D.C. 1985. A phylogeny of primitive frogs (Archaeobatrachians). Ph.D. Thesis, University of Kansas, Lawrence, Kansas.
- Carlson, J. (Coordinator, Montana Animal Species of Concern Committee). 2003. Montana Animal Species of Concern. Helena, MT: Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks. In Press. 12p.
- Chrapliwy, P.S. and J.S. Findley. 1956. Records of the central plains spadefoot toad, Scaphiopus bombifrons Cope, in South Dakota and Wyoming. Herpetologica 12: 124.
- Cook, F.R. 1960. New localities for the plains spadefoot toad, tiger salamander, and the great plains toad in the Canadian prairies. Copeia 1960 (4): 363-364.
- Cooper, S.V., C. Jean, and P. Hendricks. 2001. Biological survey of a prairie landscape in Montana’s glaciated plains. Report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 24 pp. plus appendices.
- Cope, E.D. 1863. On Trachycephalus, Scaphiopus and other American Batrachia. Proceedings of the Academy of Natural Sciences of Philadelphia 15: 43-54.
- Cope, E.D. 1863. Proceedings of the Academy of National Sciences, Philadelphia. Volume 15, p. 53.
- Cope, E.D. 1872. Report on the recent reptiles and fishes of the survey, collected by Campbell Carrington and C.M. Dawes. pp. 467-469 In: F.V. Hayden, Preliminary report of the United States geological survey of Montana and portions of adjacent territories; being a fifth annual report of progress. 538 pp. 42nd Congress, 2nd Session, House Executive Document Number 326. Serial 1520.
- Cope, E.D. 1875. Check-list of North American Batrachia and Reptilia; with a systematic list of the higher groups, and an essay on geographical distribution. Based on the specimens contained in the U.S. National Museum. U.S. Natioanl Museum Bulletin 1: 1-104.
- Cope, E.D. 1889. The Batrachia of North America. Bulletin of the U.S. National Museum 34: 1-525, figs. 1-119, pls. 1-86.
- Corn, P.S., E. Muths, and W.M. Iko. 2000. A comparison in Colorado of three methods to monitor breeding amphibians. Northwestern Naturalist 81:22-30.
- Crother, B.I. (ed.) 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico. SSAR Herpetological Circular No. 37:1-84.
- Dimmitt, M.A. and R. Ruibal. 1980. Exploitation of food resources by spadefoot toads (Scaphiopus). Copeia (4): 854-862.
- Econ, Inc., Helena, MT., 1988, Wildlife monitoring report, 1987 field season, Big Sky Mine. March 1988. In Peabody Mining and Reclamation Plan Big Sky Mine Area B. Vol. 8, cont., Tab 10 - Wildlife Resources. Appendix 10-1, 1987 Annual Wildlife Report.
- Farrar, E.S. and J.D. Hey. 1997. Carnivorous spadefoot (Spea bombifrons Cope) tadpoles and fairy shrimp in Western Iowa. Journal of the Iowa Academy of Science 104(1): 4-7.
- Firschen, I.L. 1950. A new record of Spea bombifrons from northern Mexico and remarks on the status of the hammondii group of spadefoot group of spadefoot anurans. Herpetologica 6(3): 75-77.
- Fjell, Alan K., 1986, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1985 field season. March 1986.
- Fjell, Alan K., and Brian R. Mahan, compilers., 1984, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1983 field season. February 1984.
- Fjell, Alan K., and Brian R. Mahan., 1983, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1982 field season. May 1983.
- Fjell, Alan K., and Brian R. Mahan., 1985, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1984 field season. February 1985.
- Fjell, Alan K., and Brian R. Mahan., 1987, Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1986 field season. April 1987.
- Forester, D.C. 1969. Reproductive isolation and hybridization between the spadefoot toads (Scaphiopus bombifrons) and (Scaphiopus hammondii) in west Texas. Unpublished M.S. Thesis, Texas Tech University, Lubbock, Texas.
- Forester, D.C. 1973. Mating call as a reproductive isolating mechanism between Scaphiopus bombifrons and Scaphiopus hammondii. Copeia 1973(1): 60-67.
- Forester, D.C. 1975. Laboratory evidence for potential gene flow between two species of spadefoot toads Scaphiopus bombifrons and Scaphiopus hammondii. Herpetologica 31(3): 282-286.
- Gates, M.T. 2005. Amphibian and reptile baseline survey: CX field study area. Report to Billings and Miles City Field Offices of Bureau of Land Management. Maxim Technologies, Billings, MT. 28pp + Appendices.
- Gilmore, R.J. 1924. Notes on the life history and feeding habits of the spadefoot toad of the western plains. Colorado College Publications in Science 13(1): 1-12.
- Gilmore, R.J. 1929. Life history and feeding habits of the spadefoot toad. Journal of the Colorado-Wyoming Academy of Science 1(1): 41.
- Gilmore, R.J. 1934. The tadpole of the spadefoot toad. Journal of the Colorado-Wyoming Academy of Science 1(6): 76
- Goldberg, S.R. and C.R. Bursey. 2002. Helminths of the plains spadefoot, Spea bombifrons, the western spadefoot, Spea hammondii, and the Great Basin spadefoot, Spea intermontana (Pelobatidae). Western North American Naturalist 62(4):491-495.
- Hall, J.A. 1998. Scaphiopus intermontanus. Catalogue of American Amphibians and Reptiles 650.1-650.17.
- Hendricks, P. and J. D. Reichel. 1996. Preliminary amphibian and reptile survey of the Ashland District, Custer National Forest: 1995. Montana Natural Heritage Program, Helena, MT. 79 p.
- Hendricks, P. and J. D. Reichel. 1998. Amphibian and reptile survey on Montana refuges: 1996. Montana Natural Heritage Program, Helena, MT. 19 p.
- Holycross, A.T. and K.B. Malmos. 1992b. Spea bombifrons (Plains spadefoot). Herpetological Review 23(1): 25.
- Hossack, B. and P.S. Corn. 2001. Amphibian survey of Medicine Lake National Wildlife Refuge Complex: 2001. USGS Northern Rocky Mountain Science Center, Aldo Leopold Wilderness Research Institute, Missoula, MT. 13 p.
- Hoyt, D.L. 1960. Mating behavior and eggs of the Plains spadefoot. Herpetologica 16: 199-201.
- Hughes, N. 1965. Comparison of frontoparietal bones of Scaphiopus bombifrons and Scaphiopus hammondii as evidence for interspecific hybridization. Herpetologica 21: 196-201.
- Johnson, K.H., G.L. Kurtz, R.A. Olson and T.D. Whitson. 1994. Spea bombifrons (Plains Spadefoot) Herpetological Review 25(2): 75.
- Justus, J.T., M. Sandomir, T. Urquhart and B.O. Ewan. 1977. Developmental rates of two species of toads from the desert southwest. Copeia 1977(3): 592-594.
- Kellog, R. 1932. Notes on the spadefoot of the western plains (Scaphiopus hammondii). Copeia 1932(1): 36.
- Klassen, M.A. 1990. Spadefoot spring. Nature Canada 19: 8-9.
- Kluge, A. G. 1966. A new pelobatine frog from the lower Miocene of South Dakota with a discussion of the evolution of the Scaphiopus-Spea complex. Contributions of Science to the Natural History Museum of Los Angeles County 113: 1-26.
- Landreth, H.F. and M.T. Christensen. 1971. Orientation of the Plains spadefoot toad, Scaphiopus bombifrons, to solar cues. Herpetologica: 27(4): 454-461.
- Lauzon, R.D. and P. Balagus. 1998. New records from the northern range of the plains spadefoot toad (Spea bombifrons) in Alberta. Canadian Field Naturalist 112: 506-509.
- Lewin, V. 1963. The herpetofauna of southeastern Alberta. Can. Field-Nat. 77:203-214.
- Lomolino, M.V. and G.A. Smith. 2004. Terrestrial vertebrate communities at black-tailed prairie dog (Cynomys ludovicianus) towns. Biological Conservation 115(1):89-100.
- Lynch, C. 2001. North American Amphibian Monitoring Program's Montana frog-call survey: report on year two of a program in south-central Montana started April 2001 and completed in June 2001. Zoo Montana Conservation Through Education Program, Billings MT. 12 p.
- Mabry, C.M. and J.L. Christiansen. 1991. The activity and breeding cycle of Scaphiopus bombifrons in Iowa. Journal of Herpetology 25(1): 116-119.
- Matthews, W.L. 1979. Wibaux-Beach wildlife baseline study - nongame species. Bureau of Land Management, Miles City, MT. 93 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 USFS Region 1, Order Number 43-0343-0-0224. University of Montana, Wildlife Biology Program. Missoula, MT. 161 p.
- McAllister, C.T., C.R. Bursey, and D.B. Conn. 2005. Endoparasites of Hunter's spadefoot, Scaphiopus hurterii and plains spadefoot, Spea bombifrons (Anura: Scaphiododidae), from southern Oklahoma. Texas Journal of Science 57(4):383-389.
- McEneaney, T. and J. Jensen. 1974. The reptiles and amphibians of the Charles M. Russell National Wildlife Range - 1974. Charles M. Russell National Wildlife Refuge. Lewistown, MT. 3 p.
- Moore, G.A. 1937. The spadefoot toad under drought conditions. Copeia 1937(4): 225-226.
- Moore, J.E. 1952. The spadefoot toad, Scaphiopus, in Alberta. Copeia 1952: 278.
- Morlan, R.E. and J.V. Matthews, Jr. 1992. Range extension for the plains spadefoot, Scaphiopus bombifrons, inferred from owl pellets found near outlook, Saskatchewan. Canadian Field Naturalist 106(3): 311-315.
- Nero, R.W. 1959. The Spadefoot toad in Saskatchewan. Blue Jay 17(1): 41-42.
- Ott, J.A. and D.E. Scott. 1999. Effects of toe-clipping and PIT-tagging on growth and survival in metamorphic Ambystoma opacum. Journal of Herpetology 33(2): 344-348.
- Peterson, C.R., C.J. Askey, and D.A. Patla. 1993. Amphibians and reptiles along the Grand Loop and Fountain Freight Roads between Madison Junction and Biscuit Basin in Yellowstone National Park. 26 July, 1993. Greater Yellowstone Ecosystem Amphibian Survey and Monitoring Program, Herpetology Laboratory, Department of Biological Sciences, Idaho State University, Pocatello, ID. 45 p.
- Pfening, K.S. 2003. A test of alternative hypotheses for the evolution of reproductive isolation between spadefoot toads: support for the reinforcement hypothesis. Evolution 57(12):2842-2851.
- Pfennig, K.S. and M.A. Simovich. 2002. Differential selection to avoid hybridization in two toad species. Evolution 56(9): 1840-1848.
- Pfenning, D.W. 1990. The adaptive significance of an environmentally-cued development switch in an anuran tadpole. Oecologia 85:101-107.
- Pfenning, D.W. 1992. Proximate and functional causes of polyphenism in an anuran tadpole. Functional Ecology 6:167-174.
- Pfenning, D.W., H.K. Reeve and P.W. Sherman. 1993. Kin recognition and cannibalism in spadefoot toad tadpoles. Animal Behaviour 46(1): 87-94.
- Pierce, J.R. 1976. Distribution of two mating call types of the plains spadefoot (Scaphiopus bombifrons) in southwestern United States. Southwest Naturalist: 20(4): 578-582.
- Plummer, M.V. and G. Turnipseed. 1982. Scaphiopus bombifrons (Plains spadefoot). Herpetological Review 13(3): 80.
- Plumpton, D.L. and R.S. Lutz. 1993. Prey selection and food habits of burrowing owls in Colorado. Great Basin Naturalist 53: 299-304.
- Potthoff, T.L. and J.D. Lynch. 1986. Interpopulation variability in mouthparts in Scaphiopus bombifrons in Nebraska (USA) (Amphibia: Pelobatidae). Prairie Naturalist 18(1): 15-22.
- Powder River Eagle Studies, Inc., Gillette, WY., 1999, Spring Creek Mine 1998 Wildlife Monitoring. March 1999.
- Powder River Eagle Studies, Inc., Gillette, WY., 2000, Spring Creek Mine 1999 Wildlife Monitoring. March 2000.
- Powder River Eagle Studies, Inc., Gillette, WY., 2000, Spring Creek Mine 2000 Wildlife Monitoring. March 2000.
- Preston, W.B. and D.R.M. Hatch. 1986. The Plains spadefoot (Scaphiopus bombifrons) in Manitoba (Canada). Canadian Field Naturalist 100(1): 123-125.
- Rauscher, R.L. 1998. Amphibian and reptile survey on selected Montana Bureau of Reclamation impoundments. Montana Department of Fish, Wildlife and Parks, Nongame Program. Bozeman, MT. 24 pp.
- Reichel, J. and D. Flath. 1995. Identification of Montana's amphibians and reptiles. Montana Outdoors 26(3):15-34.
- Reichel, J.D. 1996. Preliminary amphibian and reptile survey of the Helena National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 87 pp.
- Reichel, J.D. 1997. Amphibian, reptile and northern bog lemming survey on the Rocky Mountain Front: 1996. Montana Natural Heritage Program, Helena, MT. 81 p.
- Roedel, M.D. and P. Hendricks. 1998. Amphibian and reptile survey on the Bureau of Land Management Lewistown District: 1995-1998. Montana Natural Heritage Program, Helena, MT. 53 p.
- Roedel, M.D. and P. Hendricks. 1998b. Amphibian and reptile inventory on the Headwaters and Dillon Resource Areas in conjunction with Red Rocks Lakes National Wildlife Refuge: 1996-1998. Montana Natural Heritage Program, Helena, MT. 46 p.
- Sadler, L.M. and M.A. Elgar. 1994. Cannibalism among amphibian larvae: A case of good taste. Trends in Ecology and Evolution 9(1): 5-6.
- Sattler, P.W. 1978. Biochemical genetic investigations of introgressive hybridization and systematic relationships in the spadefoot toads, genus Scaphiopus. Ph.D. Dissertation, Texas Technical University.
- Sattler, P.W. 1985. Introgressive hybridization between the spadefoot toads Scaphiopus bombifrons and Scaphiopus multiplicatus (Salientia: Pelobatidae). Copeia 1985(2): 324-332.
- Sexton, O.J. and K.R. Marion. 1974. Probable predation by Swainson’s hawks on swimming spadefoot toads. Wilson Bulletin 86(2): 167-168.
- Shannon, F.A. 1953. Scaphiopus bombifrons, a state record for Arizonia. Herpetologica 9: 127-128.
- Simovich, M.A. 1985. Analysis of a hybrid zone between the spadefoot toads (Scaphiopus multiplicatus) and (Scaphiopus bombifrons). Ph.D. diss., University of California, Riverside, CA.
- Simovich, M.A. 1994. The dynamics of a spadefoot toad (Spea multiplicata and S. bombifrons) hybridization system. Pp. 167-182 in P.R. Brown and J.W. Wright, eds. Herpetology of North American deserts, special publication no. 5. Southwestern Herpetolo
- Simovich, M.A. and C.A. Sassaman. 1986. Four independent electrophoretic markers in spadefoot toads. Journal of Heredity 77(6): 410-414.
- Simovich, M.A., C.A. Sassamam, and A. Chovnick. 1991. Post-mating selection of hybrid toads (Scaphiopus multiplicatus and Scaphiopus bombifrons). Proceedings of the San Diego Society of Natural History 1991: 1-6.
- Smith, H.M., C.E. Bock and J.H. Bock. 1993b. Spea bombifrons (Plains spadefoot). Herpetological Review 24(4): 154.
- Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
- Stebbins, R.C. 1985. A field guide to western reptiles and amphibians. Houghton Mifflin Company, Boston. 336 pp.
- Sullivan, B.K. 1985. Sexual selection and mating system variation in anuran amphibians of the Arizona-Sonoran desert. Great Basin Naturalist 45(4): 688-696.
- Sullivan, B.K. and E.A. Sullivan. 1985. Variation in advertisement calls and male mating success of Scaphiopus bombifrons, Scaphiopus couchi and Scaphiopus multiplicatus (Pelobatidae). Southwestern Naturalist 30(3): 349-356.
- Swanson, D.L. and B.M. Graves. 1995. Supercooling and freeze intolerance in overwintering juvenile spadefoot toads (Scaphiopus bombifrons). Journal of Herpetology 29(2): 280-285.
- Tanner, V.M. 1939. A study of the genus Scaphiopus. The spade-foot toads. Great Basin Naturalist 1: 3-23.
- Tanner, W.W. 1989b. Status of Spea stagnalis Cope (1875), Spea intermontanus Cope (1889), and a systematic review of Spea hammondii Baird (1839) (Amphibia: Anura). Great Basin Naturalist 49(4): 503-510.
- Timken, R. No Date. Amphibians and reptiles of the Beaverhead National Forest. Western Montana College, Dillon, MT. 16 p.
- Trauth, S.E., B.P. Butterfield, and W.E. Meshaka, Jr. 1989. Scaphiopus bombifrons (plains spadefoot). Herpetological Review 20(1): 12.
- Trowbridge, A.H. and M.S. Trowbridge. 1937. Notes on the clevage rate of Scaphiopus bombifrons Cope, with additional remarks on certain aspects of its life history. American Naturalist 71(736): 460-480.
- Trowbridge, M. 1941. Studies on the normal development of Scaphiopus bombifrons Cope. I. The clevage period. Transactions of the American Microscopical Society 60: 508-526.
- Trowbridge, M. 1942. Studies on the normal development of Scaphiopus bombifrons Cope. II. The later embryonic and larval periods. Transactions of the American Microsopical Society 61: 66-83.
- Turner, F.B. 1951. A checklist of the reptiles and amphibians of Yellowstone National Park with incidental notes. Yellowstone Nature Notes 25(3): 25-29.
- Turner, F.B. 1955. Reptiles and amphibians of Yellowstone National Park. Yellowstone Interpretive Series No. 5. Yellowstone Library and Museum Association. Yellowstone National Park, WY. 40 p.
- Van Kirk, R., L. Benjamin, and D. Patla. 2000. Riparian area assessment and amphibian status in the watersheds of the Greater Yellowstone Ecosystem. Greater Yellowstone Coalition, Bozeman, MT. 102 p.
- Vitt, L.J., J.P. Caldwell, and D.B. Shepard. 2005. Inventory of amphibians and reptiles in the Billings Field Office Region, Montana. Sam Noble Oklahoma Museum of Natural History and Department of Zoology, University of Oklahoma, Norman, OK. 33 pp.
- Voss, W.J. 1961. Rate of larval development and metamorphosis of the spadefoot toad, Scaphiopus bombifrons. Southwestern Naturalist 6: 168-174.
- VTN Colorado, Inc. Decker Coal Company., 1975, Draft environmental impact assessment for the proposed North Extension of the West Decker Mine.
- Werner, J.K., B.A. Maxell, P. Hendricks and D.L. Flath. 2004. Amphibians and Reptiles of Montana. Mountain Press Publishing Company: Missoula, MT. 262 pp.
- Wheeler, G.C. and J. Wheeler. 1966. The amphibians and reptiles of North Dakota. University of North Dakota, Grand Forks, ND. 104 pp.
- Wiens, J.J. 1989. Ontogeny of the skeleton of Spea bombifrons (Anura: Pelobatidae). Journal of Morphology 202(1): 29-52.
- Wiens, J.J. and T.A. Titus. 1991. A phylogenetic analysis of Spea (Anura: Pelobatidae). Herpetologica 47(1): 21-28.
- Woodward, B.D. 1982. Sexual selection and nonrandom mating patterns in desert anurans (Bufo woodhousei, Scaphiopus couchi, S. multiplicatus, and S. bombifrons). Copeia 1982(2): 351-355. 28.
- Woody, J.R. 1967. Study of certain meteorological influences on the emergence and breeding with notes on the embryology of the plains spadefoot toad, Scaphiopus bombifrons. M.A. Thesis, University of Northern Colorado, Greely, 72 pp.
- Woody, J.R. and B.O. Thomas. 1966. Preliminary studies of the Scaphiopus bombifrons in northeastern Colorado. Journal of the Colorado-Wyoming Academy of Science 5(7): 11-12.
- Woody, J.R. and B.O. Thomas. 1968. Study of certain meterological influences on the emergence and breeding of the plains spadefoot toad, Scaphiopus bombifrons. Journal of the Colorado-Wyoming Academy of Science 6(1): 11.
- Yarrow, H.C. 1882. Check list of North American reptilia and batrachia, with catalogue of specimens in the U.S. National Museum. United States National Museum Bulletin 24. 249 p.
- Zweifel, R.G. 1968b. Reproductive biology of anurans of the arid southwest, with emphasis on adaptation of embryos to temperature. Bulletin of the American Museum of Natural History 140(1): 1-64.