Boreal Toad

Anaxyrus boreas boreas (Bufo boreas boreas)

Boreal Toad

Distribution in Wyoming

 

 

 

 

 

 

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The Boreal Toad is a subspecies belonging to the Western Toad complex of Anaxyrus boreas. Its range extends from Alaska south along the Rocky Mountains, passing through Wyoming, Colorado, and reaching into the northern tip of New Mexico. In Wyoming it is restricted to the montane and subalpine life zones between 7,500 and 11,500 feet in the western and south central regions of the state. It inhabits the lakes, ponds, marshes, meadows, and streamside riparian habitats of the coniferous forest. It is a highly terrestrial species and is sometimes found considerable distances from permanent water.

Boreal Toad Boreal Toad

It is a stocky toad, 3 to 4 inches long (SVL), with a tan or deeper brown (occasionally dark olive to almost black) background and with a white stripe running midline along its back. Its rough and somewhat dry skin is covered extensively with rounded glands, the largest of which is the oblong shaped parotoid gland located just posterior to the eye. The face of each gland is often highlighted with a veneer of rusty orange and the edges bordered by irregular patterns of greenish splotches. The sides and belly are more granular than warty, lighter in color, and blemished with numerous black flecks. The throat and pelvic regions are often darkened with muted yellow or dull pink. It is distinguished from other species of toads in Wyoming by lacking cranial ridges between the orbits of the eye.

Boreal Toad Boreal Toad

They exist in the high country where winter is long and the growing season short. Consequently, their reproductive cycle demands a strategy that begins early, proceeds rapidly, and ends with enough time to acquire sufficient body reserves to assure survival during the upcoming winterís hibernation. At the upper limits of its distribution, breeding commences as soon as snowmelt has progressed enough to liberate the toad from its hibernacula and when ice-off has occurred along the warming northern shores of ponds and the isolated shallow sections of larger lakes.

Though males lack vocal sacs, they do produce a series of chirps which function as a release call when clasped by other males. These vocalizations may be useful to lure females in the nearby vicinity; however, they are probably ineffective invitations at distances greater than 50 yards.

Boreal Toad Boreal Toad

During mating, the male will clasp the female just behind her front limbs (known as axillary amplexus) and above the enlargement in her body containing the eggs. With male passenger clinging to her back, she moves through the shallows releasing her eggs in a long gelatinous string as the male sheds his sperm and fertilizes them. The string will contain 5,000 to 10,000 eggs and be many feet long. To the casual observer happening upon the scene, it might appear as though a kitten had unraveled a ball of yarn.

About 5-10 days after fertilization, the developing embryos hatch into black or dark-brown tadpoles; these in turn undergo metamorphosis 6-10 weeks later. Individuals generally enter hibernacula by late September. Reproductive maturity is obtained 3-4 years later.