Mammals are the only living members of Synapsida; this clade, together with Sauropsida (reptiles and birds), constitutes the larger Amniota clade. Early synapsids are referred to as "pelycosaurs." The more advanced therapsids became dominant during the Guadalupian. Mammals originated from cynodonts, an advanced group of therapsids, during the Late Triassic to Early Jurassic. Mammals achieved their modern diversity in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, and have been the dominant terrestrial animal group from 66 million years ago to the present.
The basic mammalian body type is quadrupedal, with most mammals using four limbs for terrestrial locomotion; but in some, the limbs are adapted for life at sea, in the air, in trees or underground. The bipeds have adapted to move using only the two lower limbs, while the rear limbs of cetaceans and the sea cows are mere internal vestiges. Mammals range in size from the 30–40 millimetres (1.2–1.6 in) bumblebee bat to the 30 metres (98 ft) blue whale—possibly the largest animal to have ever lived. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which lay eggs. The most species-rich group is the viviparousplacental mammals, so named for the temporary organ (placenta) used by offspring to draw nutrition from the mother during gestation.
Domestication of many types of mammals by humans played a major role in the Neolithic Revolution, and resulted in farming replacing hunting and gathering as the primary source of food for humans. This led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, and ultimately the development of the first civilizations. Domesticated mammals provided, and continue to provide, power for transport and agriculture, as well as food (meat and dairy products), fur, and leather. Mammals are also hunted and raced for sport, kept as pets and working animals of various types, and are used as model organisms in science. Mammals have been depicted in art since Paleolithic times, and appear in literature, film, mythology, and religion. Decline in numbers and extinction of many mammals is primarily driven by human poaching and habitat destruction, primarily deforestation. (Full article...)
The elk, or wapiti (Cervus canadensis), is the second largest species of deer in the world and one of the largest mammals in North America and eastern Asia. In the deer family (Cervidae), only the moose, Alces alces (called an "elk" in Europe), is larger. Wapiti are almost identical to red deer found in Europe, of which they were long believed to be a subspecies; they have recently been determined to be a distinct species based on DNA evidence. Elk range in forest and forest-edge habitat, feeding on grasses, plants, leaves and bark. Although native to North America and eastern Asia, they have adapted well to countries where they have been introduced, including New Zealand and Argentina. Their high level of adaptability poses a threat to endemic species and ecosystems where they have been introduced. Male elk have large antlers which are shed each year. Males engage in ritualized mating behaviors during the rut, including posturing, antler wrestling and bugling, a loud series of screams which establishes dominance over other males and attracts females. The bugle call is one of the most distinctive calls in nature. Elk are susceptible to a number of infectious diseases, some of which can be transmitted to livestock. Efforts to eliminate infectious diseases from elk populations, largely through vaccination, have had mixed success. Some cultures revere the elk as a spiritual force. In parts of Asia, antlers and their velvet are used in traditional medicines. Elk are hunted as a game species; the meat is leaner and higher in protein than beef or chicken.
...that one burrow of the eastern chipmunk(pictured) was found to contain 390 acorns?
.. that the Hare Indian dog, now extinct, was not known to bark, but puppies learned to imitate the barking of other dogs when the breed was introduced to Europe?
Sheep are quadrupedalruminants, typically kept as livestock. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it generally refers to Ovis aries. One of the first animals to be domesticated, sheep are likely descended from the wild mouflon of Europe and Asia. They are raised for their fleece, meat, and milk.
The kob (Kobus kob) is an antelope found across Central Africa and parts of West Africa and East Africa. It is closely related to the reedbucks and waterbucks and similar in appearance to the impala but more heavily built. Kob have few strong social bonds, but females can live in herds numbering in the thousands. Males are generally territorial, although on densely-populated floodplains some males live in clustered territories known as leks.
The skull of a black rhinoceros (Diceros bicornis), a critically endangered species of rhinoceros native to eastern and central Africa. The two horns on the skull are made of keratin, with the larger front horn typically 50 cm (20 in) long. Sometimes, a third, smaller horn may develop.
The meerkat (Suricata suricatta) is a small member of the mongoose family native to the Kalahari Desert of southern Africa. They are social animals, living underground in groups of 20 to 50 members. Although the name means "lake cat" in Dutch, meerkats are not cats, nor are they attracted to lakes.
The European bison or wisent (Bison bonasus) is the heaviest of the surviving land animals in Europe, with males growing to around 1,000 kg (2,200 lb). European bison were hunted to extinction in the wild, but have since been reintroduced from captivity into several countries. This male is moulting, his winter coat coming off in clumps.
The polar bear (Ursus maritimus) is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. A boar (adult male) weighs around 350–750 kilograms (770–1,650 lb), while a sow (adult female) is about half that size. Polar bears are the largest land carnivores currently in existence, rivalled only by the omnivorous Kodiak bear. Although it is the sister species of the brown bear, it has evolved to occupy a narrower ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice and open water, as well as for hunting seals, which make up most of its diet. Although most polar bears are born on land, they spend most of their time on sea ice. The species's scientific name, which is derived from this fact, means 'maritime bear'. Because of their dependence on sea ice, polar bears are categorized as marine mammals. Due to expected habitat loss caused by global warming, the polar bear is classified as a vulnerable species. For decades, large-scale hunting raised international concern for the future of the species, but populations have rebounded after controls and quotas began to take effect.
A female Parma Wallaby (Macropus parma) and her joey. This wallaby species is the smallest member of the genus Macropus, at between 3.2 and 5.8 kilograms (7.1 and 12.8 lb) and about 50 centimetres (1.6 ft) in length. It was believed to be extinct before the end of the 19th century, but a population was found on Kawau Island in 1965, and two years later another population was found in the forests near Gosford, New South Wales. They are now classified as Near Threatened.
A portrait of a cheetah at Whipsnade Zoo in Bedfordshire. Cheetahs have small and streamlined heads. Their ears are small, short, and rounded, marked by black patches on the back and tawny edges. Their high-set eyes have round pupils, while their whiskers are fine and inconspicuous. Their faces have unique "tear streak" markings that may serve to reduce glare or define facial expressions.
The skull of the African buffalo (Syncerus caffer), a large African bovine. It has a long but stocky body and short but thickset legs, resulting in a relatively short standing height. The adult bull’s horns, as shown here, have fused bases, forming a continuous bone shield known as a "boss".
A giraffe extending its tongue to feed. Its tongue, lips and palate are tough enough to deal with sharp thorns in trees. Giraffes prefer trees of the genera Acacia, Commiphora and Terminalia. A giraffe requires less food than typical grazing animals, typically consuming 65 pounds (29 kg) of leaves and twigs daily, because the foliage it eats has more concentrated nutrition and it has a more efficient digestive system.
Off the coast of Juneau, Alaska, a group of 15 Humpback Whales works in tandem to catch herring using the bubble net feeding technique, in which they exhale through their blowholes, creating a ring of bubbles up to 30 m (100 ft) in diameter. The whales then suddenly swim upwards through the bubble net swallowing thousands of fish in each gulp.
The Golden-mantled Ground Squirrel (Spermophilus lateralis) is a species of squirrel native throughout North America and can be found in a wide variety of forest habitats as well as rocky meadows, and even sagebrush flats. It can be identified by its chipmunk-like stripes and coloration, but unlike chipmunks, it lacks any facial stripes.
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