|Scientific Name:||Anaxyrus boreas|
|Species Authority:||(Baird & Girard, 1852)|
Bufo boreas Baird and Girard, 1852
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Geoffrey Hammerson, Georgina Santos-Barrera, Erin Muths|
|Reviewer(s):||Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)|
Listed as Near Threatened because this species is probably in significant decline (but probably at a rate of less than 30% over ten years) because of disease (including chytridiomycosis), thus making the species close to qualifying for Vulnerable.
|Range Description:||This species occurs along the Pacific Coast of North America from southern Alaska (Wiedmer and Hodge 1996) to Baja California, and ranges eastward to the Rocky Mountains in west-central Alberta, Montana, Wyoming, Utah (Ross et al. 1995), Colorado (Hammerson 1999), and (formerly) northern New Mexico (Degenhardt, Painter and Price 1996). It is absent from most of the desert south-west (Stebbins 1985b). Its altitudinal range extends from sea level to at least 3,640m asl.|
Native:Canada; Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total adult population size of the species is unknown but is likely to exceed 100,000. It is still common in much of its range. The Rocky Mountain populations in Colorado and Wyoming have undergone a drastic decline since the 1970s (Corn, Stolzenburg and Bury 1989; Hammerson 1989, 1992, 1999; Carey 1993; Muths et al. 2003). It has also declined greatly in the Yosemite area of the Sierra Nevada, California (Drost and Fellers 1996). It is apparently undergoing localized declines in Yellowstone National Park (Peterson, Koch and Corn 1992), Montana (Reichel and Flath 1995), and elsewhere (Olson 1989).|
|Habitat and Ecology:||This species is found in a wide variety of habitats including desert springs and streams, meadows and woodlands and mountain wetlands. It is also known from around ponds, lakes, reservoirs, and slow-moving rivers and streams. It digs its own burrow in loose soil or uses those of small mammals, or shelters under logs or rocks. The eggs and larvae develop in shallow areas of ponds, lakes, or reservoirs, or in pools of slow-moving streams.|
|Major Threat(s):||The extent of threat across the species' range is not known with certainty. The decline in the Southern Rocky Mountains is not due to acidification of breeding habitats (Corn and Vertucci 1992). Carey (1993) hypothesized that some environmental factor or synergistic effects of more than one factor might stress the toads, causing suppression of the immune system or indirectly causing immunosuppression by causing elevated secretion of adrenal cortical hormones; immunosuppression, coupled with the apparent effect of cold body temperatures on the ability of the immune system to fight disease, might lead to infection by Aeromonas hydrophila bacteria (which causes "red-leg") or other infectious agents and subsequently to death of individuals and the extirpation of populations. Die-offs in the southern Rockies have been associated with chytrid fungus infections (Muths et al. 2003). Eggs are highly susceptible to the pathogenic fungus Saprolegnia ferax, which might be introduced during fish stocking (Kiesecker and Blaustein 1997). Another possibility is that declines are related to the sensitivity of eggs to increased levels of ultraviolet radiation (Blaustein et al. 1994), but see Corn and Muths (2002) for an alternative viewpoint. In the Cascade Range of Oregon, persistent predation of adults by ravens during the toad breeding season appears to have contributed significantly to some population declines (Olson 1992). Possibly significant predation by birds has also been observed in Colorado and Idaho. The decline might be related, at least in part, to habitat destruction and degradation, water retention projects, predation by, and competition with, native and non-native species, fishery management activities, or other factors, but these factors have not been adequately assessed.|
|Conservation Actions:||This species occurs in many national parks, wildlife refuges, and wilderness areas in the US where habitat destruction is not a major threat. In Mexico, it is found within Parque Nacional Sierra de San Pedro Martir. It is listed as an endangered species in the state of Colorado and is warranted but precluded from US federal endangered species status.|
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Blackburn, L., Nanjappa, P. and Lannoo, M.J. 2001. An Atlas of the Distribution of U.S. Amphibians. Ball State University, Muncie, IN, USA.
Blaustein, A.R., Hoffman, P.D., Hokit, D.G., Kiesecker, J.M., Walls, S.C. and Hays, J.B. 1994. UV repair and resistance to solar UV-B in amphibian eggs: a link to population declines. Proceedings of the Academy of Natural Sciences of Philadelphia: 1791-1795.
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Carey, C. 1993. Hypothesis concerning the causes of the disappearance of boreal toads from the mountains of Colorado. Conservation Biology: 355-362.
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Johnson, P.T.J., Lunde, K.B., Haight, R.W., Bowerman, J. and Blaustein, A.R. 2001. Ribeiroia ondatrae (Trematoda: Digenea) infection induces severe limb malformations in western toads (Bufo boreas). Canadian Journal of Zoology: 370-379.
Kiesecker, J.M. and Blaustein, A.R. 1997. Influences of egg laying behavior on pathogenic infection of amphibian eggs. Conservation Biology: 214-220.
Kiesecker, J.M., Blaustein, A.R. and Miller, C.L. 2001. Transfer of a pathogen from fish to amphibians. Conservation Biology: 1064-1070.
Livo, L.J. and Yeakley, D. 1997. Comparison of current with historical elevational range in the boreal toad, Bufo boreas. Herpetological Review: 143-144.
Muths, E. and Nanjappa, P. 2005. Western Toad. Bufo boreas Baird and Girard, 1852. In: Lannoo, M.J. (ed.), Status and Conservation of U.S. Amphibians. Volume 2: Species Accounts, pp. 64-83. University of California Press, Berkeley, California.
Muths, E., Corn, P.S., Pessier, A.P. and Green, D.E. 2003. Evidence for disease related amphibian decline in Colorado. Biological Conservation: 357-365.
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Olson, D.H. 1989. Predation on breeding western toads (Bufo boreas). Copeia: 391-397.
Olson, D.H. 1992. Ecological susceptibility of high elevation Oregon anuran amphibians to population fluctuations. Abstract, 6th Annual Meeting of the Society for Conservation Biology: p. 102.
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|Citation:||Geoffrey Hammerson, Georgina Santos-Barrera, Erin Muths 2004. Anaxyrus boreas. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 29 August 2014.|
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