Date of observation: October 26, 2013
Location: Ditch Creek
Biology: The boreal toad is one of the few amphibians found in Wyoming. The short dry summers and long cold winters are not conducive to typical life cycles of amphibians, although some have found ways to survive.
Boreal toads have tough dry skin which helps them retain water during the dry summer months. During the winter, boreal toads hibernate by burying themselves in mud. The toads emerge between May and August depending on altitude, then find their way to mating grounds. During mating season, males do not produce a mating call because they lack a vocal sac. Females lay up to two strings of 16,500 eggs, which are protected by the same poison that is released by the paratoid glands of adults (located behind the eyes) to deter predators.
Like most amphibian populations, the boreal toad population is in danger. One of the greatest pressures on amphibian populations is the chytrid (Batrachochytrium dendrobatidis), or Bd, fungus. This parasite attacks the skin of the host, causing the skin to thicken. Amphibians rely on semi-permeable skin for water and ion regulation. When amphibians are infected with the chytrid fungus, the skin loses its ability to absorb water and the host dies. The chytrid fungus destroys amphibian populations rapidly in part because amphibians gather together during mating season. If only one individual is infected with the fungus, the fungus can spread through an entire population during mating season.
The boreal toad is listed as “near threatened” on the IUCN Red List, and the range of the boreal toad is contracting. The decline of boreal toad populations has been attributed to habitat loss and degradation, pollution and the introduction of aquatic predators. Climate change will also increase the effect of the chytrid fungus on boreal toad populations.
Conservation efforts have been focused on re-introducing the boreal toad in areas where the toad was historically present, along with maintaining and preserving boreal toad habitat.
Field notes: The boreal toad was found at the bottom of a deep pool of water surrounded by steep muddy banks on Ditch Creek. The specimen appeared to be dead, with eyes closed and limbs stretched out. Ordinarily toads bury themselves in mud while hibernating. Believing the toad to be dead, I retrieved the toad from the bottom of the river. The toad slowly opened its eyes and began to move. I returned the toad to the muddy banks of the creek, hoping that I had not harmed the toad by removing it from the water. Ordinarily toads bury themselves in mud when hibernating. I assume that the toad had buried itself in mud, then had subsequently been removed from the mud through some type of disturbance.