Occurs from south-central Wyoming southward through the mountainous regions of Colorado to extreme north-central New Mexico.
Found at high elevations, 7382 to 11,811 ft, in a variety of aquatic habitats such as slow-moving streams, lakes, marshes, alpine meadows, and beaver ponds, normally associated with lodge pole pine or spruce-fir forests. Areas with still, year-round water is ideal for breeding habitat. These toads prefer water with a sloping bank as it creates a variety of water depths. Research indicates that water less than four inches deep is preferred for breeding, and is likely a cue for egg laying. Adult toads move away from breeding areas into high grasses, and surrounding forests.
Boreal toads are gray or greenish in color with considerable dark blotching on the back and belly. Both males and females have a distinct whitish stripe running down their backs. It can however be broken in to segments and is not usually visible on juvenile toads. The paratoid glands are large and oval. Toadlets are similar in appearance to adults, except for often lacking the middorsal stripe and they possess red-orange coloration on the toes.
Boreal Toad tadpoles are blackish with little or no iridescence, with the underside slightly paler and a black tail. Unlike many other species of toads, the boreal toad has no vocal sac and produces only a soft chirping sound, rather than a loud mating call.
Adult boreal toads emerge from hibernation when the snowmelt has cleared an opening from their burrow and daily temperatures remain above freezing. Males will stay within 984 feet of their breeding sites while females may travel as far as 2.4 miles away. Boreal toads can be active at temperatures as low as 37º Fahrenheit.
When threatened, boreal toads seek to escape by jumping into water and diving to the bottom.
At lower altitudes, breeding occurs at lower altitudes in May and in higher altitudes in July or early August. Females may skip one to three years between breeding attempts, depending on their physical condition. Females deposit 3,000 to 10,000 round and black eggs in a long gelatinous string. Generally, she lays two strings of eggs in the sunniest part of the breeding pond. Egg and tadpole development is temperature dependant; in high, cold locations, development from hatching to metamorphosis can take 75 days.
Males reach sexual maturity at about four years of age and females at about six years of age. The late age of first reproduction is likely due to the short amount of time available for growth each year at high elevation habitats where this toad is found.
Boreal toads may spend over half of their lives hibernating. Unfortunately, very little is known about their wintertime behavior or where they hibernate. Amphibians, like the boreal toad, that reside at more northern latitudes tend to hibernate on land rather than in the water. Over-wintering in a terrestrial environment may lower the risk of predation and does not put the animal at risk of anoxia (physiologically inadequate supply of oxygen) or hypoxia (failure of oxygen to be utilized by body tissues), a possibility for amphibians in pond environments where the frozen pond is also covered by snow.
Once common in mountain habitats between 7,000-12,000 feet in the Southern Rocky Mountains, the boreal toad population has seriously declined over the past two decades.
This is thought to be due to a combination of environmental stressors and suppression of the toad’s immune system. One such stressor may be increased UV-B exposure due to climate changes.
Another reason for the decline appears to be related to infection by the chytrid fungus, Batrachochytrium dendrobatidis. Chytrid fungus has caused severe population declines, even the complete extinction of certain amphibian populations and species—including the boreal toad. The fungus infects the frog and lives inside the cells in the outer layer of the toad’s skin, causing the skin to thicken. This thickening prevents water absorption and oxygen exchange as well as the ionic balance in the blood systems of an amphibian. Since male boreal toads tend to congregate together each year, whereas females may only breed every other year, the males are more likely to transmit the fungus to other males. Therefore, even if the population is not severely impacted by the presence of the fungus, the sex ratio of the population may become skewed beyond normal, healthy ranges.
Motorized vehicles can be another major source of toad mortality. This is particularly a problem when toads cross roads moving between their seasonal habitats—breeding ponds, foraging areas and winter hibernation sites. Extensive use of heavy equipment or off-road vehicles may collapse the shallow burrows that the toads need for wintering.
The boreal toad is presently listed as an endangered species by both Colorado and New Mexico, and is a protected species in Wyoming. The U.S. Fish and Wildlife Service had classified the Southern Rocky Mountain population of the boreal toad in 1995 as a candidate species which is "warranted but precluded" for federal listing—meaning there was adequate justification and information to warrant federal listing as threatened or endangered, but listing has been postponed.
|Did YOU Know?|
|Toads can navigate by the stars and their sense of smell to move from a pond to another water body.|
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