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NATURAL HISTORY

BOREAL TOAD } Anaxyrus boreas boreas
FAMILY: Bufonidae

DESCRIPTION: Boreal toads may reach a length of four inches. They possess warty skin and often have a distinctive light mid-dorsal stripe. Tadpoles are black or dark brown and eggs are black.

HABITAT: Boreal toads primarily occupy slow-moving streams, beaver ponds, small lakes, reservoirs, stock ponds, wet meadows, seeps, creek pools, marshy areas, wet meadows and associated woodlands.

RANGE: This toad is found in coastal Alaska south through British Columbia, western Alberta, Washington, Oregon, Northern California, Nevada, Idaho, western Montana, western and south central Wyoming, the mountains of Utah and Colorado, and extreme northern New Mexico.

MIGRATION: Boreal toads may migrate several miles from breeding ponds to winter burrows, but in most cases the distance is much shorter.

BREEDING: The minimum age of breeding boreal toads is about four years in males and six years in females. Females may skip one to three years between breeding attempts. Breeding occurs during a two to four-week period from mid-May to mid-June at lower elevations, and as late as mid-July at higher elevations. Eggs are deposited in long, double-layer jelly strings with one to three rows of eggs.

LIFE CYCLE: Eggs hatch one to two weeks after being laid. Tadpoles typically metamorphose by late July to late August. Recently metamorphosed toadlets aggregate within a few meters of the water, and move into nearby moist habitats later in summer. Adults often live more than nine years, and their maximum life span is estimated to be about 12 years.

FEEDING: Adults forage primarily on ants, beetles, spiders and other invertebrates. Tadpoles filter suspended plant material or feed on bottom detritus.

THREATS: Boreal toads are threatened by disease caused by chytrid fungus, habitat destruction, pesticides and other pollutants, the stocking of predatory fish, climate change and loss of genetic diversity.

POPULATION TREND: This species is declining throughout its range. The impacts have been especially severe in the southern Rocky Mountains, where chytrid fungus has wiped out numerous boreal toad populations.

Boreal toad photo courtesy Flickr Creative Commons/ J.N. Stuart