Frog Article Anura

General: Frog, common name for an amphibian of the order that also includes toads. Frogs are native to most parts of the world, except Antarctica, the driest deserts, and many oceanic islands, but the greatest variety are found in moist, tropical areas. Physical Characteristics: Frogs are usually small animals that have smooth, moist skin, bulging eyes, and external eardrums behind the eyes; the adults lack a tail. Frogs have long hind legs, and most species can take long leaps. Many species also have webbed feet, making them excellent swimmers. Most frogs, especially males, are quite vocal. As the frog forces air through the voice box, or larynx, the vocal cords vibrate to make calls distinctive of its species. A much louder sound is produced by the males of species that possess vocal sacs, which swell enormously when the frog calls to attract a mate. The frog's tongue is attached at the front of the mouth instead of at the rear, and it is covered with a sticky substance, making it an efficient trap. Like most amphibians, most frogs pass through a free-living fish-like larval stage before undergoing true metamorphosis into adult frogs. Many of these frogs lay their eggs in water, although some lay their eggs on vegetation above the water, in wet places on land, or even on the back of one of the parents. The breeding season varies according to species and geographic region but often coincides with heavy spring or summer rains. Tadpoles have gills and a tail, and most feed on algae and other vegetation, although a few are carnivorous and may even feed on their siblings. As tadpoles mature, the tail is absorbed, lungs develop, the gills disappear, legs appear, and the adult frog form is established. Some frogs, especially in the tropics, do not go through a larval phase; these frogs lay eggs, usually in damp places out of water, that hatch directly into frog-lets.    Red-eyed Leaf Frog Behaviour: Frogs live in a variety of habitats, but most prefer moist regions. Although they are air breathers, frogs can stay underwater for long periods, and they can breathe through the skin. Tree frogs are adapted for tree living; other frogs are permanently aquatic; still others spend most of their lives in underground burrows, coming up only to feed or breed. Like all amphibians, a frog's body temperature depends on its surroundings, and in colder regions frogs burrow in mud to hibernate. Some kinds, such as certain Australian frogs, estivate - that is, lie in a state of torpor during intense heat-after burying themselves in sand and clay. Frogs subsist principally on insects, worms, spiders, and centipedes. Aquatic frogs sometimes eat other frogs, tadpoles, and small fish. Larger frogs eat objects as large as mice or small snakes. Types of Frogs: The order containing frogs and toads is usually divided into about 22 families, based primarily on skeleton and tooth differences. The terms frog and toad are often applied somewhat arbitrarily to the members of these families. The true toads generally have drier skin, often covered with warts, and the majority spend most of their life on land. They also lack teeth, whereas frogs have teeth on their upper jaws (but not on the lower). True Frogs One large and nearly world-wide family comprises the true frogs, many species of which are well known. The bullfrog is the largest true frog in North America; it weighs up to 0.5 kg (1.2 lb) and has a total length of 46 cm (18 in). Some of the most common North American frogs are the leopard frogs, which include a number of species and which are easily recognised by the numerous black, often light-edged, spots on the back and legs. Most true frogs stay close to ponds and streams, but the North American wood frog, a small, reddish-brown species with mask-like black bands on the head, wanders far from water. The green frog is another common species in North America; despite the name, some green frogs are mostly brown. Two well-known true frogs of Europe are the common European frog, which resembles the wood frog, and the edible frog, a popular food in Europe. The African giant frog, the largest of all frogs, which grows as long as 66 cm (26 in) and weighs as much as 4.5 kg (10 lb), is also a true frog. Other Frogs The tree frogs include a large and interesting family of frogs that is found in North and South America, Europe, and Asia. This family contains members that have expanded adhesive disks at the ends of the toes, permitting them to climb on smooth surfaces. Some members of an Asian family are even more specialised for arboreal life. Their feet are webbed with fan-like structures that enable them to parachute to the ground from considerable heights without injuring themselves; they are sometimes known as flying frogs, although they do not actually fly. One of the most unusual frogs is the hairy frog, named for the hair-like skin projections that develop on the body and legs of the male during breeding season. Although frogs are generally harmless to humans, some South American frogs secrete a powerful poison through their skins.    Dart Frog Benefit to Humans: Frogs aid humans in many ways. They control insect pests in wooded areas, farms, and gardens, and several species have been introduced to various parts of the world as a defence against undesirable insects. From earliest times frogs have been widely used as food. Frogs are also important to research and medical laboratories because their skeletal, muscular, digestive, nervous, and other systems are similar to those of higher animals. Studies show a consistent decline in frog populations since about 1980, but scientists have failed to identify any direct or indirect causes. Suggested factors include acid rain, climate change, ozone depletion, habitat destruction and fragmentation, the introduction of exotic (non-native) species, and pollution. Scientific Classification: Frogs and toads make up the amphibian order Anura. True frogs make up the family Ranidae. The word frog is classified as Rana sylvatica, the green frog as Rana clamitans, the common European frog as Rana temporaria, the edible frog as Rana esculentaa, and the African giant frog as Rana goliath. The hairy frog is classified as Astylosternus robustus. True toads make up the family Bufonidae.

Home | Photos/eCards / Feature Gallery / Photos of Britain / Animal Photos | Animal Articles Games / Two Player Games / Three-Four Player Games | Links | Contact