| am / phib / i / an: an amphibious organism; especially : any of a class (Amphibia) of cold-blooded vertebrates (as frogs, toads, or salamanders) intermediate in many characters between fishes and reptiles and having gilled aquatic larvae and air-breathing adultsAt all life stages, amphibians are food for fish, birds, reptiles, mammals, and even invertebrates and other amphibians. In their turn, amphibians consume vast quantities of insects and other invertebrates, many considered pests by humans. Comprising mostly frogs, toads, and salamanders, much about amphibians is captured in their name: �double life.� This refers to the complex life cycle of amphibians, with most having an aquatic stage as a gilled �tadpole� before going through a remarkable metamorphosis to become air-breathing, four-limbed adults. Most species deposit jelly-like eggs in water, where the tadpoles then hatch and mature. Even amphibian species that lead largely terrestrial lives never escape the requirement to maintain a moist skin. This is because amphibians use their porous skin to supplement breathing, a feat that requires moisture to be efficient. Recent estimates indicate that the number of described amphibian species globally (4 780) exceeds that of mammals (4 629). While 64% (29 species) of amphibians are Secure, nearly a quarter (22%, 10 species) are designated At Risk or May Be At Risk. This precarious state may in part be explained by living a life at their ecological and geographic limits. Yet human-caused factors, like draining of wetlands and forest clearing or fragmentation, are also threats to the persistence of amphibian species in Canada. Besides loss of habitat, amphibians are also thought to be more sensitive and more widely exposed to a host of environmental stresses by virtue of their aquatic and terrestrial life stages and porous skins. There are about 4 780 amphibian species globally. Canada is home to 45 species of amphibians � 24 frogs and toads and 21 salamanders. Ontario has more amphibian species (23) than any other province or territory. Canada is home to 45 species of amphibians. Twenty-nine (64%) amphibian species in Canada are considered Secure. Four (9%) amphibian species in Canada are considered At Risk. Amphibians are believed to be environmental indicator species. Globally, populations of many amphibian species are believed to be declining. |
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