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Frogs are a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (Ancient Greek an-, without + oura, tail). The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is found in tropical rainforests. There are approximately 4,800 recorded species, accounting for over 85% of extant amphibian species. They are also one of the five most diverse vertebrate orders.
The body plan of an adult frog is generally characterized by a stout body, protruding eyes, cleft tongue, limbs folded underneath and the absence of a tail. Besides living in fresh water and on dry land, the adults of some species are adapted for living underground or in trees. The skin of the frog is glandular, with secretions ranging from distasteful to toxic. Warty species of frog tend to be called toads. Frog warts are elevations in the skin where glandular toxins tend to concentrate. The distinction between frogs and toads is based on informal naming conventions concentrating on the warts rather than taxonomy or evolutionary history; some toads are more closely related to frogs than other toads. Frogs' skins vary in colour from well-camouflaged dappled brown, grey and green to vivid patterns of bright red or yellow and black to advertise toxicity and warn off predators.
Frogs typically lay their eggs in water. The eggs hatch into aquatic larvae, called tadpoles, that have tails and internal gills. They have highly specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets. The life cycle is completed when they metamorphose into adults. A few species deposit eggs on land or bypass the tadpole stage. Adult frogs generally have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. Frogs are extremely efficient at converting what they eat into body mass, which makes them an important food source for predators. Frogs are a keystone group in the food web dynamics of many of the world's ecosystems. The skin is semi-permeable, making them susceptible to dehydration, so they either live in moist places or have special adaptations to deal with dry habitats. Frogs produce a wide range of vocalizations, particularly in their breeding season, and exhibit many different kinds of complex behaviours to attract mates, to fend off predators and to generally survive.
Frog populations have declined significantly since the 1950s. More than one third of species are considered to be threatened with extinction and over one hundred and twenty are believed to have become extinct since the 1980s. The number of malformations among frogs is on the rise and an emerging fungal disease, chytridiomycosis, has spread around the world. Conservation biologists are working to understand the causes of these problems and to resolve them. Frogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion.
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Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 to 60 cm. Most geckos cannot blink, but they often lick their eyes to keep them clean and moist. They have a fixed lens within each iris that enlarges in darkness.
Geckos are unique among lizards in their vocalizations. They use chirping sounds in social interactions with other geckos. They are the most species-rich group of lizards, with about 1,500 different species worldwide. The New Latin gekko and English "gecko" stem from the Indonesian-Malay gēkoq, which is imitative of the sound the animals make.
All geckos, excluding the Eublepharidae family, lack eyelids and instead have a transparent membrane, which they lick to clean. Nocturnal species have excellent night vision; their eyes are 350 times more sensitive to light than the human eye.
Most gecko species can lose their tails in defense, a process called autotomy. Many species are well-known for their specialized toe pads that enable them to climb smooth and vertical surfaces, and even cross indoor ceilings with ease (one hypothesis explains the ability in terms of the van der Waals force). These antics are well-known to people who live in warm regions of the world, where several species of geckos make their home inside human habitations. These species (for example the house gecko) become part of the indoor menagerie and are often welcomed, as they feed on insects, including mosquitoes. Unlike most lizards, geckos are usually nocturnal and are great climbers.
The largest species, the kawekaweau, is only known from a single, stuffed specimen found in the basement of a museum in Marseille, France. This gecko was 60 cm (24 in) long and it was likely endemic to New Zealand, where it lived in native forests. It was probably wiped out along with much of the native fauna of these islands in the late 19th century, when new invasive species such as rats and stoats were introduced to the country during European colonization. The smallest gecko, the Jaragua sphaero, is a mere 1.6 cm long and was discovered in 2001 on a small island off the coast of the Dominican Republic.
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Gibbons are apes in the family Hylobatidae. The family historically contained one genus, but now is split into four genera. Gibbons occur in tropical and subtropical rainforests from northeast India to Indonesia and north to southern China, including the islands of Sumatra, Borneo, and Java.
Also called the lesser apes, gibbons differ from great apes (chimpanzees, gorillas, orangutans, bonobos and humans) in being smaller, exhibiting low sexual dimorphism, in not making nests, and in certain anatomical details in which they superficially more closely resemble monkeys than great apes do. But like all apes, gibbons evolved to become tailless. Gibbons also display pair-bonding, unlike most of the great apes. Gibbons are masters of their primary mode of locomotion, brachiation, swinging from branch to branch for distances of up to 15 m (50 ft), at speeds as high as 55 km/h (34 mph). They can also make leaps of up to 8 m (26 ft), and walk bipedally with their arms raised for balance. They are the fastest and most agile of all tree-dwelling, non-flying mammals.
Depending on species and gender, gibbons' fur coloration varies from dark to light brown shades, and anywhere between black and white. It is rare to see a completely white gibbon.
Gibbon species include the siamang, the white-handed or lar gibbon, and the hoolock gibbons.
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Gorillas constitute the eponymous genus Gorilla, the largest extant genus of primates by size. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. The genus is divided into two species and either four or five subspecies. The DNA of gorillas is highly similar to that of a human, from 95–99% depending on what is counted, and they are the next closest living relatives to humans after the bonobo and common chimpanzee.
Gorillas' natural habitats cover tropical or subtropical forests in Africa. Although their range covers a small percentage of Africa, gorillas cover a wide range of elevations. The mountain gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200–4,300 metres (7,200–14,100 ft). Lowland gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda.
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Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. The term "ground sloth" is used as a reference for all extinct sloths because of the large size of the earliest forms discovered, as opposed to the extant "tree sloths." However, this is a historical convention and does not imply that all extinct sloths were strictly terrestrial in nature. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, radiocarbon dating suggests an age of between 2819 and 2660 BCE for the last known occurrence of Megalocnus in Cuba. Ground sloths had been extinct on the mainland of North and South America for 10,000 years or more. Their later survival in the Caribbean correlates with the later colonization of this area by humans. Some insular sloth populations persisted 5,000-6,000 years longer than their continental mainland relatives, in congruence with the global pattern of late Quaternary large vertebrate extinction due to human dispersal.
The bulk of ground sloth evolution took place during the mid to late Tertiary of South America while the continent was isolated. At their earliest appearance in the fossil record, the ground sloths were already distinct at the family level. The presence of intervening islands between the American continents in the Miocene allowed a dispersal of forms into North America. A number of mid- to small-sized forms are believed to have previously dispersed to the Antilles islands either by making short swims or using land bridges. Ground sloths were a hardy group as evidenced by their diverse numbers and dispersals into remote areas given the finding of their remains in Patagonia (Cueva del Milodón) and parts of Alaska.
Sloths, and xenarthrans as a whole, represent one of the more successful South American groups during the Great American Biotic Interchange. During the interchange, many more taxa moved from North America into South America than in the other direction. At least five genera of ground sloths have been identified in North American fossils; these are examples of successful immigration to the north.
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Gulls or seagulls are seabirds of the family Laridae in the sub-order Lari. They are most closely related to the terns (family Sternidae) and only distantly related to auks, skimmers, and more distantly to the waders. Until the twenty-first century most gulls were placed in the genus Larus, but this arrangement is now known to be polyphyletic, leading to the resurrection of several genera. An older name for gulls is mew, cognate with German "Möwe", Dutch "meeuw" and French "mouette"; this term can still be found in certain regional dialects.
Gulls are typically medium to large birds, usually grey or white, often with black markings on the head or wings. They typically have harsh wailing or squawking calls, stout, longish bills, and webbed feet. Most gulls, particularly Larus species, are ground-nesting carnivores, which will take live food or scavenge opportunistically. Live food often includes crabs and small fish. Gulls have unhinging jaws which allow them to consume large prey. Apart from the kittiwakes, gulls are typically coastal or inland species, rarely venturing far out to sea. The large species take up to four years to attain full adult plumage, but two years is typical for small gulls. Large White-Headed Gulls are typically long-lived birds, with a maximum age of 49 years recorded for the Herring Gull.
Gulls nest in large, densely packed noisy colonies. They lay two to three speckled eggs in nests composed of vegetation. The young are precocial, being born with dark mottled down, and mobile upon hatching.
Gulls—the larger species in particular—are resourceful, inquisitive and intelligent birds, demonstrating complex methods of communication and a highly developed social structure. For example, many gull colonies display mobbing behaviour, attacking and harassing would-be predators and other intruders. Certain species (e.g. the Herring Gull) have exhibited tool use behaviour, using pieces of bread as bait with which to catch goldfish, for example. Many species of gull have learned to coexist successfully with humans and have thrived in human habitats. Others rely on kleptoparasitism to get their food. Gulls have been observed preying on live whales, landing on the whale as it surfaces to peck out pieces of flesh.
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Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera.
Hamsters are crepuscular and remain underground during the day to avoid being caught by predators. In the wild, they feed primarily on seeds, fruits, and vegetation, and will occasionally eat burrowing insects. They have elongated cheek pouches extending to their shoulders in which they carry food back to their burrows. Hamsters tend to sleep during the day and are wide awake at night, which may be irritating to some people because of their cage-biting and wheel-running.
Hamster behavior varies depending on their environment, genetics, and interaction with people. Because they are easy to breed in captivity, hamsters are often used as laboratory animals. Hamsters have also become established as popular small house pets, and are sometimes accepted even in areas where other rodents are disliked, and their typically solitary nature can reduce the risk of excessive litters developing in households.
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Hares and jackrabbits are leporids belonging to the genus Lepus. A hare less than one year old is called a leveret. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare (Caprolagus hispidus), and three species known as red rock hares (Pronolagus spp.).
Hares are very fast-moving animals; the European brown hare (Lepus europaeus) is able to run at speeds of up to 56 km/h (35 mph). The five species of jackrabbit found in central and western North America are able to run at 64 km/h (40 mph), and can leap up to 3m (ten feet) at a time. They live solitarily or in pairs, while a "drove" is the collective noun for a group of hares.
A common type of hare in Arctic North America is the snowshoe hare, replaced farther south by the black-tailed jackrabbit, white-tailed jackrabbit, and other species.
Normally a shy animal, the European brown hare changes its behavior in spring, when hares can be seen in broad daylight chasing one another around meadows; this appears to be competition between males to attain dominance (and hence more access to breeding females). During this spring frenzy, hares can be seen "boxing"; one hare striking another with its paws (probably the origin of the term "mad as a March hare"). For a long time, this had been thought to be intermale competition, but closer observation has revealed it is usually a female hitting a male to prevent copulation.
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Hawk is a common name for some birds of prey, widely distributed and varying greatly in size.
Owls are members of the order Strigiformes and are not hawks.
The common names of some birds include the term "hawk", reflecting traditional usage rather than taxonomy, such as referring to an Osprey as a "fish hawk" or the Buteo species B. jamaicensis as a Red-tailed Hawk.
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Herring are forage fish, mostly belonging to the family Clupeidae. They often move in large schools around fishing banks and near the coast. The most abundant and commercially important species belong to the genus Clupea, found particularly in shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea, as well as off the west coast of South America. Three species of Clupea are recognised, and provide about 90% of all herrings captured in fisheries. Most abundant of all is the Atlantic herring, providing over half of all herring capture.
Herring played a pivotal role in the history of marine fisheries in Europe, and early in the twentieth century their study was fundamental to the evolution of fisheries science. These oily fish also have a long history as an important food fish, and are often salted, smoked, or pickled.
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