Great Plains Toad - Anaxyrus cognatus
State Rank Reason (see State Rank above)
Current trend is unknown due to a scarcity of observations, but long-term declines are possible due to declines in ephemeral waterbodies (bison wallows). Species faces threats from habitat loss including development of native habitat, and reduced availability of burrows due to black-tailed prairie dog declines.
- Details on Status Ranking and Review
ScoreG - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment233,208 square Kilometers from Natural Heritage Program range maps
ScoreA - Very Large Decline (decline of >90%, with <10% of population size, range extent, area occupied, and/or number or condition of occurrences remaining)
CommentHistoic data sugest that this species made extensive use of buffalo wallows for breeding which may indicate a substanital decline in available breeding habitat
ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentRecent calling surveys recorded few observations of this species.
ScoreB - Moderate and imminent threat. Threat is moderate to severe and imminent for a significant proportion (20-60%) of the population or area.
CommentLoss of habitat due to conversion of native prairie to agriculture. Loss of hibernacula/ burrow systems due to prairie dog declines. Water quality of breeding sites. Lack of knowledge to assess threats.
SeverityModerate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
ScopeModerate - 20-60% of total population or area affected
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).
CommentSpecies mature in 2-3 years, produce thousands of eggs with low survival
ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
CommentPlains /xeric landscapes near drainages and waterbodies
Raw Conservation Status Score
3.5 + 0 (geographic distribution) + 0 (environmental specificity) + -0.5 (long-term trend) + -0.75 (threats) = 2.25
Laid communally in single or more rarely double strings containing 1,342 to 45,054 eggs (Bragg 1937a, Krupa 1994). Each ovum is black above, shaded progressively lighter to white below. There are two jelly layers surrounding each ovum, including the outer jelly layer that composes the string (Bragg 1937a). Ovum diameters are approximately 1.2-1.3 mm, but total egg diameters, including the two jelly layers are approximately 2.0 mm. The jelly string is constricted between eggs to approximately 1.7 mm (Bragg 1937a).
Mottled brown and gray dorsally with a light greenish-yellow and reddish iridescence ventrally (Bragg 1936). The dorsal tail fin is dendritically pigmented and highly arched while the ventral tail fin is of uniform width and transparent (Bragg 1936). The dorsal pattern of large, paired blotches appears before metamorphosis is complete. The upper mandible is highly arched and labial tooth rows are usually 2/3 with oral papillae restricted to the sides of the mouth. Eyes are located dorsally. Total length (TL) of 8-29 mm (Bragg 1936, Bragg 1940a).
JUVENILES AND ADULTS
The skin is covered with numerous small warts. Juveniles typically have reddish colored warts. A white stripe usually extends down the center of the back and large paired green to brown blotches are present dorsally. These blotches are outlined or separated by white bands. The ventral side is cream to white colored (Krupa 1990). Large parotid glands are present behind the eyes. The underside of the hind foot often has a sharp-edged tubercle and a smaller dark-tipped tubercle. Except for small metamorphs, a large bony plate or hard lump (boss) covers the snout from the tip to the front of the eyes. In addition, cranial crests are present behind the eyes and converge toward the boss on the snout to form a “V” between the eyes (Krupa 1990). Snout-vent length (SVL) of males is typically less than 95 mm and females can reach up to 115 mm (Bragg 1937b; Bragg 1940a; Krupa 1990). Males have dark, loose throat skin and a dark patch on the inner surface of the innermost digit of the forefeet during breeding. The vocal sac, when inflated, may extend beyond the front of the face.
The geographic range of Western Toad (Anaxyrus boreas
) does not overlap with the geographic range of Great Plains Toad and adult Western Toad lack cranial crests. If present in Montana, the Canadian Toad (Anaxyrus hemiophrys
) are probably limited to the extreme northeast corner of the state and adults either lack or have weakly developed cranial crests behind the eyes.
Although overlap in habitat use exists, Woodhouse’s Toad (Anaxyrus woodhousii
) seem to be more commonly associated with sandy soils on floodplains while the Great Plains Toad is more commonly associated with heavier soils in upland habitats (Timken and Dunlap 1965). Eggs and larvae of Woodhouse’s and Great Plains Toad are very similar and may not be differentiable by even thoroughly trained herpetologists. However, Woodhouse's Toad tadpoles lack the strongly arched tail fin and eggs are enclosed in a single jelly layer. In addition, eggs and larvae of Woodhouse’s Toad are much more likely to be found in permanent or semi-permanent waters than those of Great Plains Toad (Bragg 1940a). Adult Woodhouse’s Toad lack the shield or ‘boss’ on the tip of the snout and have “L” shaped cranial crests between and behind each eye. Metamorph Woodhouse’s Toad lack the large paired dorsal blotches that are present on Great Plains Toad (Bragg 1937b).
Western Hemisphere Range
The Great Plains Toad is recognized as a distinct species. The range consists of the Great Plains from central Mexico to southeastern Alberta and in the desert southwest as far west as eastern California and as far north as southern Utah. Great Plains Toad can be found at elevations up to 2,440 m (8,000 ft) (Stebbins 2003, Goebel 1996). In Montana they have been sparsely documented across the plains east of Shelby, Great Falls, Lewiston, and Billings.
Maximum elevation: 1,319 m (4327 ft) Hensley Creek drainage, 20.3 km E of Warner Hill, N of Columbus in Stillwater County (Grover, Cole and Dell Despain MTNHP 2010).
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 is available specific to Montana. Elsewhere the species is known to migrate up to several hundred meters between breeding pools and nonbreeding terrestrial habitats.
Little specific information on the habitat of Great Plains Toad is available. The Great Plains Toad can be found in floodplain habitats but are more common in upland grasslands with harder packed soils (Bragg 1940a, Smith and Bragg 1949, Timken and Dunlap 1965). Great Plains Toads have been reported from sagebrush-grassland, rainwater pools in road ruts, in stream valleys, at small reservoirs and stock ponds, and around rural farms; breeding has been documented in small reservoirs and backwater sites along streams (Mosimann and Rabb 1952, Dood 1980, Hendricks 1999, Hossack et al. 2003). When inactive, adults lie dormant in rodent or self-excavated burrows and under rocks and wood when terrestrial conditions are not favorable. When conditions are warmer and moist, they will emerge to feed (Bragg 1937a, Smith and Bragg 1949, Dimmitt and Ruibal 1980, Flowers and Graves 1994, 1995).
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: mtnhp.org/requests
) 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
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
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
Although food habits in Montana have not been studied, adult and juvenile Great Plains Toads are generally known to eat a variety of small terrestrial invertebrates, including spiders, moths, caterpillars, flies, beetles, termites, and ants (Bragg 1937a, Smith and Bragg 1949, Dimmitt and Ruibal 1980, Flowers and Graves 1994, 1995, Hammerson 1999). Great Plains Toads require 11 to 22 feedings per year to survive. In the playa wetlands of northwest Texas, carabid beetles were the most common food (Anderson et al. 1999). Larvae are herbivorous and detritivores and eat suspended matter, organic debris, algae, and plant tissue (Bragg 1940a).
Great Plains Toads are uncommon near human habitation (Black 1970d). They are mainly nocturnal (Bragg 1940a, Black 1970d). Eggs are wrapped around vegetation on the pond bottom and hatch in 2-3 days (Bragg 1937a, Bragg 1940a). Tadpoles metamorphose in 18 to 45 days (Bragg 1937b, Bragg 1940a, Krupa 1994). Post-metamorphic young may form aggregations (Graves 1993). Creusere and Whitford (1976) found individuals 1,600 meters from the nearest breeding site but is likely that they range farther than this. Population explosions and mass unidirectional migrations have been reported for local areas as well as regions as large as several thousand square miles in area (Bragg and Brooks 1958).
This species enters water only to breed after late spring and summer rains when minimum temperatures are above 12 °C (Bragg 1937a, Bragg 1940a, Krupa 1994). It breeds almost exclusively in clear and shallow temporary waters including rain pools, flooded areas, and ponds and reservoirs that fluctuate in size. Great Plains Toad appear to prefer breeding in stock tanks and roadside ponds rather than floodplains (Baxter and Stone 1985). Eggs and larvae develop in shallow water, usually clear or slightly turbid, but not muddy.
From information gathered in Oklahoma, breeding choruses usually last a few days but are of variable duration. They lasted up to 14 days in March but only 1 to 2 days in June (Krupa 1994). Clutch size was usually several thousand eggs that hatch in a few days. The larval period was short (as few as 18 days) in June and long (up to 49 days) in early spring. Pools rarely held water long enough for larvae to reach metamorphosis (Krupa 1994). Great Plains Toads are sexually mature in 2 to 5 years. The species commonly exhibits communal egg deposition (Krupa 1994).
In Montana, Great Plains toads have been documented breeding in temporary pools of flooded grasslands in May to July (Bragg 1940a, Black 1970d). Two of three females collected in north-central Montana on July 20 had well developed eggs (Mosimann and Rabb 1952).
The following was taken from the Status and Conservation section for the Great Plains Toad account in Maxell et al. 2009
In the past 150 years Great Plains Toads have only been documented at about 30 localities across the plains east of the Rocky Mountains and at the present time their status across this region is almost completely unknown. Risk factors relevant to the viability of populations of this species are likely to include grazing, use of pesticides and herbicides, nonindigenous species, road and trail development, on- and off-road vehicle use, development of water impoundments, habitat loss/fragmentation, and metapopulation impacts, all as described above. However, the lack of information on the distribution, status, habitat use, and basic biology of the species may currently represent the greatest risk to the viability of the species (i.e., the species could have undergone, or currently be undergoing, drastic declines but we lack any kind of baseline information that would allow us to make such a determination). Individual studies that specifically identify risk factors or other issues relevant to the conservation of the Great Plains Toad include the following. (1) Bragg (1937a) reports that all Great Plains Toad eggs in pools that were heavily contaminated with fecal material from cattle died while other eggs in nearby uncontaminated pools survived. (2) Several authors report that large numbers are killed on highways by motor vehicles (Bragg 1940a, Bragg and Brooks 1958, Hammerson 1999). Bragg and Brooks (1958) report a mean of 60 individuals per 30 linear feet of highway were killed on roads in North Dakota and Minnesota during a population explosion and mass migration event. (3) Hammerson (1999) notes that several populations have been extirpated due to residential and commercial development in Colorado. (4) Stuart (1995) found exotic American Bullfrogs (Lithobates catesbeianus
) preying on Great Plains Toads. (5) Great Plains Toads often occupy Prairie Dog (Cynomys
sp.) burrows and these burrows may serve as critical refugia for the species (Craig Knowles, Fauna West Wildlife Consultants, pers. comm.).
- Literature Cited AboveLegend: View Online Publication
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- Bragg, A.N. 1937a. A note on the metamorphosis of the tadpoles of Bufo cognatus. Copeia 1937: 227-228.
- Bragg, A.N. 1937b. Observations on Bufo cognatus with special references to breeding habits and eggs. American Midland Naturalist 18: 273-284.
- Bragg, A.N. and M. Brooks. 1958. Social behavior in juveniles of Bufo cognatus Say. Herpetologica 14: 141-147.
- Creusere, F.M. and W.G. Whitford. 1976. Ecological relationships in a desert anuran community. Herpetologica 32: 7-18.
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- Flowers, M.A. and B.M. Graves. 1994. Feeding ecology of juvenile great plains toad (Bufo cognatus) and woodhouse's toad (Bufo woudhousii). North Dakota Academy of Science Proceedings. 48: 22
- Flowers, M.A. and B.M. Graves. 1995. Prey selectivity and size-specific diet changes in Bufo cognatus and Bufo woudhousii during early postmetamorphic ontogeny. Journal of Herpetology 29(4): 608-612.
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- Mosimann, J.E. and G.B. Rabb. 1952. The herpetology of Tiber Reservoir Area, Montana. Copeia(1): 23-27.
- Smith, C.C. and A.N. Bragg. 1949. Observations on the ecology and natural history of Anura, VII. Food and feeding habits of the common species of toads in Oklahoma. Ecology 30(3): 333-349.
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- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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- Additional Sources of Information Related to "Amphibians"