Woodhouse's Toad - Anaxyrus woodhousii
(see State Rank Reason below)
State Rank Reason (see State Rank above)
Species is apparently secure and not at risk of extirpation or facing significant threats in all or most of its range.
- Details on Status Ranking and Review
Woodhouse's Toad (Anaxyrus woodhousii) Conservation Status Review
Review Date = 05/03/2018
ScoreF - 20,000-200,000 km squared (about 8,000-80,000 square miles)
Comment194,937 square Kilometers from Natural Heritage Program range maps
ScoreD - Moderate Decline (decline of 25-50%)
CommentMany riparian habitats (prairie stream pool habitats) have been lost to land use changes over the last century. However species readily uses reservoirs and other man-made waterbodies if available. A net loss of habitat is likely since European arrival.
ScoreE - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation
CommentPopulations appear stable based on lentic surveys conducted over the last 15 years. Species was detected regularly during 2016 calling surveys.
ScoreH - Unthreatened. Threats if any, when considered in comparison with natural fluctuation and change, are minimal or very localized, not leading to significant loss or degradation of populations or area even over a few decades’ time. (Severity, scope, and/or immediacy of threat considered Insignificant.)
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
CommentThis species has high fecundity, a moderate age of maturity, and recruitment can be low.
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.
CommentDistributed widely across shrublands, grasslands, and badlands. Appears to use a range of lentic waterbody types for breeding
Raw Conservation Status Score
3.5 + 0 (geographic distribution) + 0 (environmental specificity) + 0 (short-term trend) + 1 (threats) = 4.5
Laid in long single or double strands containing up to or greater than 28,493 eggs (Smith 1934, Krupa 1995a). Each ovum is black above, gray below, and is loose within the outer jelly string (Smith 1934). Ovum diameters are 1.0 to 1.4 mm, but total egg diameters, including the outer jelly string are approximately 3.5 mm (Smith 1934).
Body and tail musculature are black to dark brown with gold flecking dorsally and laterally and gray to white ventrally (Youngstrom and Smith 1936). The dorsal tail fin is dendritically pigmented, and the ventral tail fin is clear. Total length (TL) of 2.5 to 35 mm (Youngstrom and Smith 1934, Hammerson 1999).
JUVENILES AND ADULTS
Except for small metamorphs, parallel cranial crests are found on the snout and behind the eyes in the shape of an “L”. Large parotid glands are present behind the eyes. The post-orbital crests typically touch the paratoid glands. If a lump is present on the snout, it does not extend back between the eyes. Very young transformed toads typically lack the dorsal line and often have reddish warts. Adults have dry skin with small warts and each hind foot has two dark digging ‘spades’ on their soles. A white stripe extends down the center of the back on adults and is surrounded by a green and creamy-yellowish mottling with greener toward the center line and creamier yellow toward the lateral surface. Usually completely white ventrally, but some black spotting may be present (Bragg 1940b, Maxell et al. 2009). Snout-vent length (SVL) of adults is 63.5-127 mm (Smith 1934, Underhill 1960).
Calls are loud and can carry over a distance of 800 meters (approximately 2,625 feet) (Bryce Maxell, personal communication). Calls are high-pitched nasal "waaaaaaaaah" that sounds lie a crying baby, lasting 2-10 seconds and repeated regularly or irregularly (Werner et al. 2004).
See the geographic range of Western Toad (Anaxyrus boreas
) for possible areas of overlap. Adults of the Western Toad lack cranial crests and are rarely found in areas far from forests. The Canadian toad (Anaxyrus hemiophrys
), if present, is likely to only occur in the extreme northeast corner of the state and has a lump between the eyes and frequently has the paratoid gland separate from the post-orbital crest, which is often broken.
Although overlap in habitat use exists the Great Plains Toad (Anaxyrus cognatus
) is more commonly associated with heavier soils in upland habitats (Timken and Dunlap 1965). Adults of the Great Plains Toad have a raised shield on the tip of the snout and the cranial crests between their eyes diverge to form a “V”. The Great Plains Toad has large, white-bordered, dark dorsal blotches. Metamorphs of the Great Plains Toad have large paired dorsal blotches.
Eggs and larvae of Western Toad, Great Plains Toad, and Canadian Toad are very similar and may not be differentiable by even thoroughly trained herpetologists. However, eggs and larvae of Great Plains Toad are more likely to be found in temporary waters (Bragg 1940a).
Western Hemisphere Range
The systematics of the Woodhouse’s Toad species complex have a long history, but most authors now seem to agree that allozyme and call differentiation studies support evidence for the existence of two subspecies. These subspecies range from southern Texas to northern Montana and North Dakota, across the desert southwest to northern Utah, and as isolated populations in Idaho, Washington and California (Stebbins 2003, Conant and Collins 1998, Gergus 1994 as cited in Sullivan et al. 1996b, Sullivan et al. 1996b). Across this range they have been reported at elevations up to 2,440 m (8,000 ft) (Hammerson 1999). Only the Woodhouse’s Toad (Bufo w. woodhousii) is present in Montana and they have been documented across the plains east of Livingston and Fort Benton and south of the Milk and Missouri Rivers.
Maximum elevation: 1,326 m (4,350 ft) in Rosebud County (FWP Prairie Fish Survey Crew, MTNHP 2007).
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)
The Woodhouse’s Toad can be found in upland habitats with harder soils around areas with permanent waters. They are most common in floodplain and moist grassy areas around water that have loose sandy soils or muddy bottoms (Bragg 1940b, Timken and Dunlap 1965, Black 1970d, Baxter and Stone 1980). Many records from eastern Montana are in non-forested habitats, but some occur in transition vegetation, including ponderosa pine and savannah forests (Black 1970d). Adults shelter under surface debris, in rodent burrows, or in shallow, self-excavated burrows when terrestrial conditions are not favorable (Bragg 1940b, Smith and Bragg 1949, Clarke 1974a, Labanick and Schleuter 1977, Flowers and Graves 1995, Swanson et al. 1996). Egg strings are wrapped around vegetation in shallow areas of lakes, reservoirs, river backwaters, floodplain pools, and irrigation ditches (Black 1970d, Maxell et al. 2009). Juveniles may not normally move greater than 200 m from natal sites, but individuals are known to disperse up to 2 km from natal breeding sites (Breden 1988).
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
Forest and Woodland Systems
Human Land Use
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Human Land Use
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Tadpoles feed on algae and detritus, while adults feed on a variety of invertebrates. Adults have been known to collect under streetlights and feed on insects. Stomach contents can account for up to 16% of body weight. (Youngstrom and Smith 1936, Bragg 1940b, Breden 1988, Flowers and Graves 1995).
The Woodhouse’s Toad is believed to be one of the most versatile and wide-ranging toads regarding distribution (Black 1970d). Temperatures of 20 to 30 °C are most favorable for nocturnal activity. During the day, individuals remain under cover of rocks or burrowed in soil or damp cover near water (Hammerson 1982). Adults are known to live up to 19 years of age (Engeman and Engeman 1996).
Breeding and egg laying are spread out over spring and early summer (April to July) in streams, rivers, irrigation ditches, in shallow water without strong current (Black 1970d). Breeding takes place during or after spring or summer rains when temperatures are at least 10 °C. Choruses may form in drier weather and larger breeding choruses may only form at or above 16 °C (Breden 1988). Tadpoles hatch within three days and usually transform in 5-8 weeks (Youngstrom and Smith 1936; Bragg 1940b; Breden 1988).
The following was taken from the Status and Conservation section for the Woodhouse’s Toad account in Maxell et al. 2009
Woodhouse’s Toads are widely distributed and common in river valleys, smaller water courses with pools, and artificial permanent water bodies on the prairies east of the Rocky Mountains and island mountain ranges. However, their status north of the Missouri River is largely uncertain. Risk factors relevant to the viability of populations of this species are likely to include grazing, nonindigenous species and their management, road and trail development and on- and off-road vehicle use, development of water impoundments, and habitat fragmentation, all as described above. Individual studies that specifically identify risk factors or other issues relevant to the conservation of Woodhouse’s Toad include the following. (1) Taylor et al. (1999) found that Woodhouse’s Toad adults exposed to 0.0011 mg of Malathion per gram of toad (a level similar to levels commonly applied) suffered 40% mortality rates. Furthermore, when exposed to Malathion and subsequently injected with the bacteria Aeromonas hydrophila
the mortality rate increased. Thus, the application of the pesticide clearly reduced the immune function of Woodhouse’s Toads. Similarly, Ferguson and Gilbert (1967) found juveniles of the Woodhouse’s Toad to be very sensitive to the insecticides aldrin and dieldrin, but found that animals collected from sites that were contaminated with these chemicals exhibited up to a 200-fold increase in resistance over animals collected from pristine sites. Finally, Sanders (1970a) studied the sensitivities of larval Woodhouse’s Toads to 18 pesticides and herbicides and found most of them to result in high rates of mortality when exposed for 48 or 96 hours. However, a number of pesticides and herbicides had significant impacts on survival after a 24-hour exposure. The extent of the application of these herbicides and pesticides in Montana is not known, but it is likely that both herbicides and pesticides represent lethal and sublethal threats to Woodhouse’s Toad populations. (2) Bragg (1940b) and Hammerson (1999) both report that thousands of Woodhouse’s Toads are killed by or on roads near breeding sites. Furthermore, Barrass (1986) found that noise associated with highway traffic alters the reproductive behavior of Woodhouse’s Toads. Animals were less likely to move toward a breeding chorus and were more likely to call closer to one another in an established chorus in the presence of highway noise. (3) Freda and Dunson (1986) found embryos were intolerant of low pH (pH < 4.0) in the lab and were absent from all ponds with pH lower than 4.1. Furthermore, they found that larvae grew significantly slower in waters with pH less than 6.0. Pierce and Montgomery (1989) exposed larvae to short term acidic conditions (three days in water at pH = 4.0) and found that while short term exposures temporarily reduced the growth rates of individuals, long-term effects on growth, size at metamorphosis, and time to metamorphosis were not evident. (4) Many toad larvae are unpalatable to fish and may, therefore, have some resistance to the impacts of fish introductions. Kruse and Stone (1984) found that largemouth bass (Micropterus salmoides
) learned to avoid feeding on Woodhouse’s Toad tadpoles because of their unpalatability and aggregative behavior. However, bass did still prey on some tadpoles and the indirect effects of fish may still have considerable consequences. For example, Lawler (1989) found Woodhouse’s Toad tadpoles to greatly reduce activity levels in the presence of a fish predator. This decreases their foraging efficiency and increases their larval period, which exposes them to other predators for a longer period of time. (5) Bragg (1940b) reports that they are preyed upon by American Bullfrogs (Lithobates catesbeianus
). (6) Bragg (1940b) notes that young toads are commonly used as fish bait in Oklahoma.
- Literature Cited AboveLegend: View Online Publication
- Barrass, A.N. 1986. The effects of highway traffic noise on the phonotactic and associated reproductive behavior of selected anurans. Dissertation Abstracts International B Sciences and Engineering 46(8): 2609.
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- Bragg, A.N. 1940b. Observations on the ecology and natural history of Anura II. Habits, habitat, and breeding of Bufo woodhousei woodhousei (Girard) in Oklahoma. American Midland Naturalist 24: 306-321.
- Breden, F. 1988. Natural history and ecology of Fowler's toad (Bufo woodhousei fowleri) (Amphibia: Bufonidae), in the Indiana Dunes National Lakeshore (USA). Fieldiana Zoology No. 49: 1-16.
- Clarke, R.D. 1974a. Activity and movement patterns in a population of Fowler's toad, Bufo woodhousei fowleri. American Midland Naturalist 91: 140-147.
- Conant, R. and J.T. Collins 1998. A field guide to reptiles and amphibians of eastern and central North America. Third edition, expanded. Houghton Mifflin Company. Boston, MA. 616 p.
- Engeman, R.M. and E.M. Engeman. 1996. Longevity of Woodhouse's toad in Colorada. Northwestern Naturalist 77: 23.
- Ferguson, D.E. and C.C. Gilbert. 1967. Tolerances of three species of anuran amphibians to five chlorinated hydrocarbon insecticides. Journal of Mississippi Academy of Sciences 13: 135-138.
- 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.
- Freda, J. and W.A. Dunson. 1986. Effects of low pH and other chemical variables on the local distribution of amphibians. Copeia 1986(2): 454-466.
- Gergus, E.W.A. 1994. Systematics and biogeography of Bufo microscaphus (Anura: Bufonidae), with a preliminary report on americanus group phylogeny. M.S. Thesis, San Diego State University.
- Hammerson, G.A. 1982. Bullfrog eliminating leopard frogs in Colorado? Herpetological Review 13: 115-116.
- Hammerson, G.A. 1999. Amphibians and reptiles in Colorado. University Press of Colorado & Colorado Division of Wildlife. Denver, CO. 484 p.
- Krupa, J.J. 1995a. Bufo woodhousi (Woodhouse's toad). Fecundity. Herpetological Review 26: 142-144.
- Kruse, K.C., and B.M. Stone. 1984. Largemouth bass (Micropterus salmoides) learn to avoid feeding on toad (Bufo) tadpoles. Animal Behaviour 32(4):1035-1039.
- Labanick, G.M. and R.A. Schlueter. 1977. Diets of sympatric Acris crepitans and juvenile Bufo woodhousei fowleri in western Indiana. Proceedings of the Indiana Academy of Science 86: 460.
- Lawler, S.P. 1989. Behavioral responses to predators and predation risk in four species of larval anurans. Animal Behaviour 38: 1039-1047.
- Pierce, B.A. and J. Montgomery. 1989. Effects of short-term acidification on growth rates of tadpoles. Journal of Herpetology 23(2): 97-102.
- Sanders, H.O. 1970a. Pesticide toxicities to tadpoles of thet western chorus frog (Pseudacris triseriata) and Fowler's toad (Bufo woodhousei fowleri). Copeia 1970: 246-251.
- 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.
- Smith, H.M. 1934. The amphibians of Kansas. American Midland Naturalist 15(4): 377-528.
- Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
- Sullivan, B.K., K.B. Malmos and M.F. Given. 1996b. Systematics of the Bufo woodhousii complex (Anura: Bufonidae): advertisement call variation. Copeia 1996: 274-280.
- Swanson, D.L., B.M. Graves and K.L. Koster. 1996. Freezing tolerance/intolerance and cryoprotectant synthesis in terrestrially overwintering anurans in the Great Plains, USA. Journal of Comparative Physiology B Biochemistry, Systematics and Environment
- Taylor, S.K., E.S. Williams, and K.W. Mills. 1999. Effects of malathion on disease susceptibility in Woodhouse's toads. Journal of Wildlife Diseases 34(3): 536-541.
- Timken, R.L. and D.G. Dunlap. 1965. Ecological distribution of the two species of Bufo in southeastern South Dakota. Proceedings of the South Dakota Academy of Sciences 44: 113-117.
- Underhill, J.C. 1960. Breeding and growth in Woodhouse's toad. Herpetologica 16: 237-242.
- Youngstrom, K.H. and H.M. Smith. 1936. Description of the larvae of Pseudacris triseriata and Bufo w. woodhousii. American Midland Naturalist 17: 629-633.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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