Identification: A medium-sized toad, the Anaxyrus boreas halophilus has numerous rusty-colored warts (granular glands) covering its back. The toad can be several colors, including greenish, tan, reddish-brown, dusky gray, or yellow, but most are brownish-gray (Dobb 2013, California Herps 2019). Adults have a white strip down the middle of the back. The parotoid glands behind the eyes are oval and well-developed (Dobb 2013). Juvenile toads are patterned like the adults but have brightly-colored orange or yellow pads on the bottom of the feet (Dobb 2013, California Herps. 2019).
Male Anaxyrus boreas halophilus are usually less blotched than females and have smoother skin. Females are generally larger than males (California Herps 2019). Males have enlarged dark nuptial pads on the thumbs and the inner two digits of the hands, during the breeding season (Dobb 2013, California Herps 2019).
Male Anaxyrus boreas halophilus do not have a pronounced vocal sac, but they do make a soft call during the short breeding season. Their call is a high-pitched plinking sound, like the peeping of a chick, repeated several times. These calls are not used to attracting females but are considered encounter, aggressive or release calls (California Herps 2019).
Tadpoles are dark brown in color with eyes inset from the edges of the head. Their tail has a tip that is rounded. Anaxyrus boreas halophilus tadpoles grow to about 5.6 cm in length before undergoing metamorphosis (California Herps 2019).
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Anaxyrus boreas halophilus are found here.
Table last updated 5/14/2021
† Populations may not be currently present.
Ecology: Anaxyrus boreas halophilus is a habitat generalist and can be found in grasslands, deciduous and mixed-boreal forests, meadows, coastal dunes, along with human landscaped natural areas and gardens. This species occurs at higher elevations in the Sierra Nevada mountains down to sea level along the coast in southern California (Stebbins and McGinnis 2012, Dodd 2013). Adults, when not breeding, will create shallow depressions called “forms” to maintain favorable temperatures and moisture (Dodd 2013). Adult toads eat a variety of insects, arachnids, and even crayfish (Bull 2006). Experimental studies have shown that Anaxyrus boreas can track prey by odor (Dole et al. 1981).
Anaxyrus boreas halophilus like many toads uses poison secretions from parotoid glands and warts to deter predators, although some predators are immune to the poison (California Herps 2019).
Anaxyrus boreas halophilus breeding season in California is from January to July, with high elevations populations breeding later in the season. It often breeds in ponds and lakes, reservoirs, slow-flowing streams, and canals (Stebbins and McGinnis 2012). Males reach sexual maturity by four years of age and female by six (Carey 1976). Spawning produces > 16,00 eggs per female. Eggs are contained in a string of continuous jelly containing two envelopes (Stebbins and McGinnis 2012). Tadpoles feed on blue-green and green algae and complete metamorphosis in > 60 days, dependent on temperature (Dobb 2013). New metamorphs are from 10-20 mm (snout-urostyle length) (Hammerson 1999). After metamorphosis, the juvenile toads will form mass aggregations to move across the land (Dodd 2013).
References: (click for full references)
Bull, E.L. 2006. Sexual differences in the ecology and habitat selection of Western Toads (Bufo boreas) in northeastern Oregon. Herpetological Conservation and Biology 1(1):27-38.
California Herps. 2019. California toad - Anaxyrus boreas halophilus. http://www.californiaherps.com/. Accessed on 06/03/2019.
Carey, C. 1976. Thermal physiology and energetics of boreal toads, Bufo boreas boreas. Ph.D. thesis. University of Michigan, Ann Arbor, Michigan.
Collins, J.T. and T.W. Taggart. 2009. Standard common and current scientific names for North American amphibians, turtles, reptiles, and crocodilians. Sixth Edition. Publication of The Center for North American Herpetology, Lawrence. iv + 44p.
Crother, B.I. (chair). Committee on Standard and English and Scientific Names. 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Society for the Study of Amphibians and Reptiles Herpetological Circular. No. 37. iii + 86p.
Dole, J. W., Rose, B. B., and K.H. Tachiki. 1981. Western toads (Bufo boreas) learn odor of prey insects. Herpetologica 63-68.
Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. De Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, and W. C. Wheeler. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297:1-370 + Fig. 50 foldout.
Hammerson, G.A. 1999. Amphibians and reptiles in Colorado. University Press of Colorado.
McKeown, S. 1996. A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing, Inc, Los Osos, CA.
Oliver, J.A., and C.E. Shaw. 1953. The amphibians and reptiles of the Hawaiian Islands. Zoologica 38(5): 65-95.
Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company
Stebbins, R.C. and S.M. McGinnis. 2012. Amphibians and reptiles of California. Revised edition. California Natural History Guides, Berkeley, CA.
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.