Frogs spend their lives both in water and on land. These major changes in form occur under the control of hormones. Frogs breathe through their skin - perhaps toxic heavy metals and pesticides building up in aquatic food chains, plus air pollution may be killing some frogs. Unknown cause for decline. Two species of toads in the Great Lakes basin.
Toads are mainly terrestrial, but make their way to water to breed in the spring.
Song is a long melodious trill lasting 30 seconds. They change color to match their environment and are often only detected when they call. Over the last 50 years, many species of amphibians throughout the world have declined markedly in numbers. Some species have become extinct. However, towards the late 1980's biologists from many parts of the world reported declines in amphibian populations in apparently pristine habitats, such as national parks and nature reserves, where local effects could not be implicated.