Mountain-Prairie Region


boreal toad

Species Description:  In the southern Rocky Mountain population of the boreal toad (Anaxyrus boreas boreas), female boreal toads may reach a length 4.3 inches, while males seldom exceed 3.7 inches.  Both sexes have warty skin and oval parotoid glands.  Although more prominent in females, both sexes often have a distinctive light mid-dorsal stripe.  Unlike other species in the same genus, the male boreal toad has no vocal sac and, therefore, has no mating call.  In the southern Rocky Mountains adult boreal toads emerge from hibernacula when snowmelt has cleared an opening from their burrow and daily temperatures remain above freezing.  Breeding may begin in the lower altitudes in May and in the higher altitudes in July or early August.  Females may skip 1 to 3 years between breeding attempts, depending on their physical condition.  Females deposit up to 16,500 eggs in 2 strings, which are ordinarily laid in shallow 6 inches water.  Egg and tadpole development is temperature dependant; in high, cold locations, development from hatching to metamorphosis can take 75 days. 

Location: The southern Rocky Mountain population occurs from south-central Wyoming southward through the mountainous regions of Colorado to extreme north-central New Mexico.  The toads inhabit a variety of wet habitats (i.e., marshes, wet meadows, streams, beaver ponds, glacial kettle ponds, and lakes interspersed in subalpine forest) at altitudes primarily between 8,000-11,500 feet.

Threats:  A globally occurring disease of amphibians that is commonly known as chydrid fungus is believed to be the major factor in the decline of the southern Rocky Mountain population of the boreal toad. 

Recent Actions:   On May 25, 2011, the Service received a petition from the Center for Biological Diversity, Center for Native Ecosystems, and Biodiversity Conservation Alliance, requesting the agency list either the Eastern population or Southern Rocky Mountain population of the boreal toad (Anaxyrus boreas boreas) as a threatened or endangered distinct population segment (DPS) under the Endangered Species Act (Act). We have completed a 90-day petition finding for the Eastern population and Southern Rocky Mountain population of the boreal toad. We have determined that there is substantial information in the petition and in our files that the Eastern population of the boreal toad may qualify as a DPS and that listing under the Act may be warranted. Additionally, we determined that the petition and our files did not contain substantial information that the Southern Rocky Mountain population of the boreal constitutes a DPS. However, the Southern Rocky Mountain population, which includes New Mexico, Colorado, and southeastern Wyoming, is part of the larger Eastern population. The Eastern population of this amphibian occurs in portions of Colorado, Idaho, New Mexico, Nevada, Utah, and Wyoming.


More information can be found at the Service's ECOS website.

Last updated: April 11, 2012