Mountain-Prairie Region
Endangered Species Program

BOREAL TOAD

(Southern Rocky Mountain Population)


Species Description:  In the southern Rocky Mountain population, 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. 

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