Tadpoles & Frogs
Frog is the common name for amphibians in the order Anura. There is often a distinction made between frogs and toads, based on appearance, however there is no scientific distinction. more...
The only family exclusively given the common name "toad" is Bufonidae, but many species from various other families are also called "toads". "True frogs" are of the family Ranidae.
Due to the large diversity of frogs (over 4000 species), many characteristics are not shared throughout all of the species. However, there are some characteristics which distinguish them from other amphibians. Frogs are generally well suited to jumping, and have long hind legs, with elongated ankle bones. They have a short vertebral column, with no more than ten free vertebrae, followed by a fused tail bone, usually resulting in a frog with no tail.
Frogs range in size from 10mm (Psyllophryne didactyla of Brazil and Eleutherodactylus iberia of Cuba) to 300mm (Goliath frog, Conraua goliath, of Cameroon).
The skin is unkeratinized and hangs loosely on the body because of the lack of loose connective tissue, and can be smooth, warty or have skin folds. Frogs have three eyelid membranes: one transparent to protect the eyes underwater, and two which are translucent to opaque. They have a tympanum on each side of their head, which is involved in hearing, and is covered by skin in some species.
The males of most species of frogs will call for a variety of reasons. It will call by passing air through the larynx, in the throat. In most calling frogs, the sound is amplified by the vocal sac(s). The vocal sac is a membrane of skin under the throat which distends during the amplification of the call. Each call is unique to a species.
The main reason for calling is for the male to attract a mate. Males will either call in a group, called a chorus, or individually. A male frog will emit a different call when mounted by another male. Both of these calls are emitted with the mouth of the frog closed.
A distress call is emitted by some frogs when they are in a position of danger. This is done with the mouth open, and usually results in a higher pitched call. The effectiveness of the call is unknown, however it is suspected the call intrigues the predator, until another animal is attracted, distracting them enough for its escape.
Many species of frog have deep calls, or croaks. Frog noise tends to be spelt (for English speakers) as "crrrrk" in Britain and "ribbit" in the USA. This difference is due to the different species within each region(e.g. Common frog (Rana temporaria) in Britain and Leopard frog (Rana pipiens) in the USA). The croak of the American bullfrog (Rana catesbiana) is sometimes spelt "jug o' rum".
Some species of frog secrete toxins from their skin. These toxins deter predatory animals from eating them, and some are extremely poisonous to humans. Generally the frog obtains the poison from the insects or animals they eat. The Australian corroboree frogs Pseudophryne corroboree and Pseudophryne pengilleyi have been discovered to be able to manufacture a unique alkaloid which is not derived from their diet (Daly). Some natives of the Amazon area extract poison from the poison dart frog and put it on their darts when hunting. It was previously a misconception that the poison was placed on arrows rather than darts. The name of the frog was changed from poison arrow frog to poison dart frog in the early 1980's. Poisonous frogs tend to advertise their toxicity with bright colours.
Read more at Wikipedia.org