The western toad was once the most abundant toad in the western United States but has since declined in many areas. Ranging from southern Canada, and dipping into northern Mexico, this toad is still abundant in some states in the U.S. but has nearly disappeared from others. The scientific name of the western toad is Bufo boreas.
As with any toad, western toads have warts on their skin. The western toad's warts are small, roughly circular, and a reddish-brown color ringed in dark, nearly black lines. Its skin is either dark green or brown. Unlike some amphibians, western toads have horizontal pupils.
Living in a wide variety of habitats, the western toad may be found anywhere from meadows to marshes, from mountain wetlands to desert springs. This versatile habitat adaptability is one of the reasons they have been so abundant in the past. These toads dig burrows or use the abandoned burrows of small mammals for hibernation in colder months.
Although the western toad lives on land, it breeds in water. Most toads generally live near bodies of water, but the species may migrate up to 2.5 miles (4 km) to a breeding site. Eggs are laid in shallow water. Tadpoles appear in May through September and take at least two months to mature into frogs. The metamorphosis period for groups of tadpoles is highly variable and dependent on the temperature of the water in which they live: the warmer the water, the faster the tadpoles grow.
Western toads eat mostly insects. Spiders, ants, millipedes, daddy long legs, and beetles are their usual diet. They may also eat crayfish, snails, or earth worms. A wide variety of animals prey on these toads, including mammals of all sizes, as well as birds.
Although the western toad was once the most numerous of any toad species in many of the western states, this species has declined through the beginning of 21st century. The exact cause for the decline is undetermined, but many theories have been posed. Pollution reducing the immune system of otherwise healthy toads, making them susceptible to previously non-life-threatening diseases, is one theory. The thinning ozone layer, which allows more ultraviolet light to reach the earth, thus killing tadpoles, is another. Deforestation is also a clear contributor.
Scientists continue to investigate the causes for the western toad's decline. Despite declining populations however, this toad is not yet considered endangered. Although it is nearly extinct in certain areas, such as Utah, it is still relatively common in other states.