Amphibians in B.C.

Generally speaking, amphibians move between two habitats: water and uplands. The majority of amphibian species in B.C. spend most of their life on land in areas near wetlands and streams. Some research suggests they move hundreds of metres or a few kilometres into upland areas.

Frogs, toads and some salamanders lay their eggs in the spring amongst vegetation in shallow areas of wetlands, lakes, ponds and slow-moving streams. During the larval stage, they have gills and live in the water (e.g. tadpoles). Later, they transform into adults that live on land and breathe air.

A few species in B.C., such as tailed frogs and Coastal Giant Salamanders, breed in fast-flowing mountain streams. For most of these species, their young develop and change into a terrestrial form within the same year, often in late summer.

Salamanders: Not all salamanders leave the water. Some aquatic-breeding salamanders become adults in their larval form, retaining their gills and spending their entire lives in the water.

Some are called terrestrial salamanders (e.g. Western Redback Salamander) because they never enter a pond at any stage in their lives – instead, they lay their eggs on land under logs and rocks. Their young hatch looking like miniature versions of their parents and they do not transform. Terrestrial salamander species may move relatively little, potentially spending their entire life in one large log on the forest floor.

Skin: Most amphibians have smooth, moist skin that is very permeable to liquids and gases. Adult frogs absorb part of the oxygen and most of the water they need through their skin. Some salamanders (e.g. Western Redback Salamander) get all their oxygen this way since they have no lungs.

The permeable nature of their skin makes them vulnerable to pollutants or conditions that cause them to dry out or heat up (e.g. loss of forest cover). This means they need to live in moist environments and avoid being active during periods of extreme climatic conditions. Grassland amphibians of the southern interior (e.g. Great Basin Spadefoot) are the exception – they are able to cope with periods of extremely hot and dry conditions.

Cold-blooded: Amphibians are ectothermic which means they cannot generate their own body heat. To maintain a suitable body temperature, they move to micro-habitats within their environment.

Hibernation: All amphibians in temperate environments are dormant during winter months. The majority of B.C.’s amphibians seek cover underground or underwater away from freezing temperatures. A few species (e.g. Wood Frog) have a unique physiology which can withstand freezing solid in winter.

Amphibian numbers, especially frogs, have been declining for about 30 years. Entire populations and species of frogs seem to be disappearing, even from pristine areas.

In 2004, the Global Amphibian Assessment found that:

• About one third (32%) of amphibians were of conservation concern
• Amphibians were the most threatened vertebrate group in the world

Major causes of the decline include habitat loss, pollution, ozone layer depletion, and spread of disease – all factors that relate to human activities. It is important for us to learn more about these declines and to do our best to try to reverse them.

Deformities: North American amphibians have shown high levels of deformities, especially limb deformities caused by infestation of a parasite called Ribeiroia ondatrae and other environmental factors such as pesticide pollution, nutrient run-off, and increased predation pressure. Occurrences of amphibian deformities and parasite outbreaks still need be surveyed in B.C.

Diseases: Emerging infectious diseases are one of the leading causes of amphibian declines worldwide.

In B.C. there are a number of amphibian diseases that are of concern, including chytridiomycosis which is caused by Batrachochytrium dendrobatidis (Bd) or Batrachochytrium salamandrivorans (Bsal).

Amphibians not living in the wild also suffer from other diseases caused by poor health, harsh environmental conditions or poor husbandry practices. These include:

• Illnesses caused by ranaviruses in the family Iridoviridae
• Red-leg syndrome from Aeromonas sp.
• Chlamydophilosis and mycobacteriosis caused by a variety of bacteria
• Saprolegniasis caused by oomycete water molds
• Choromomycosis and basidiobolomycosis caused by a diversity of fungal pathogens
• Parasitic skin diseases caused by protozoan and invertebrate parasites

Help prevent the spread of amphibian diseases:

• Interim Hygiene Protocols for Amphibian Field Staff and Researchers (PDF)

Read about amphibian diseases and mortalities in B.C.:

• Surveillance for Amphibian Mass Mortalities in British Columbia (SAMM B.C.) (PDF)
• Sampling Protocol for Assessing Prevalence of Batrachochytrium dendrobatidis (PDF)
• Emerging Infectious Diseases in BC Amphibians (PDF)