Photography of Colorful and Poisonous Frogs By Various Photographers

The habitat of frogs extends almost worldwide, but they do not occur inÂ AntarcticaÂ and are not present on many oceanic islands.Â The greatest diversity of frogs occurs in the tropical areas of the world, where water is readily available to keep the skin moist. Some frogs inhabit arid areas such as deserts, where water may not be easily accessible, and rely on specific adaptations to survive. The Australian genusÂ CycloranaÂ and the American genusÂ PternohylaÂ bury themselves underground where they create a water-impervious cocoon in which toÂ hibernateÂ during dry periods. Once it rains, they emerge, find a temporary pond and breed. Egg and tadpole development is very fast in comparison to most other frogs so that breeding is complete before the pond dries up. Some frog species are adapted to a cold environment; for instance theÂ wood frogÂ (Rana sylvatica), whose habitat extends north of theÂ Arctic Circle, buries itself in the ground during winter when much of its body freezes.

Many frogs contain mildÂ toxinsÂ that make them unpalatable to potential predators. These include the toads, which have large poison glands, theÂ parotoid glands, located on the side of the head behind the eyes and other glands elsewhere on the body. Some frogs, such as someÂ poison dart frogs, are especially toxic. The chemical makeup of toxins in frogs varies from irritants toÂ hallucinogens,convulsants,Â nerve poisons, andÂ vasoconstrictors. Many predators of frogs have adapted to tolerate high levels of these poisons but others, including humans, may be severely affected.

Some frogs obtain poisons from the ants and other arthropods they eat;Â others, such as the AustralianÂ corroboree frogsÂ (Pseudophryne corroboreeÂ andPseudophryne pengilleyi), can manufacture anÂ alkaloidÂ not derived from their diet.Â Some native people of South America extract poison from the poison dart frogs and apply it to theirÂ dartsÂ for hunting,Â Â although few species are toxic enough to be used for this purpose. Poisonous frogs tend to advertise their toxicity with bright colours, an adaptive strategy known asÂ aposematism. There are at least two non-poisonous species of frogs in tropical America (Eleutherodactylus gaigeiÂ andÂ Lithodytes lineatus) thatÂ mimicÂ the colouration of dart poison frogs for self-protection.