Grey Wolf

The grey wolf is one of approximately 35 species belonging to the family Canidae, which includes the coyote, jackal, fox, and dog. This family is believed to have originated in North America 56.5 to 35.4 million years ago during the Eocene Epoch. The grey wolf, also called the timber wolf or white wolf, is distributed across northern Europe, Asia, and North America. It is found in a variety of habitats including mountains, plains, deserts, forests, tundra, and taiga.

F. Schneidermeyer/Oxford Scientific Films/BBC Natural History Sound Library. All rights reserved.

Brood Parasitism

The large cuckoo chick (right) is being fed in its nest by a much smaller adult bird (left). This is a good example of brood parasitism. This occurs when a bird lays its eggs in the nest of a member of its own, or another, species. The host bird will raise the young, who may eventually eject from the nest, or even kill, the host’s own natural offspring. Brood parasitism is common in this species.

Eric and David Hoskings/Corbis

Cuckoo

Young cuckoos are reared by foster parents. The adult female cuckoo chooses another bird’s nest with eggs of a similar shape, size, and colour to her own. She removes an egg and lays one in its place, carrying the stolen egg away with her. The young cuckoo almost always hatches before the other eggs in the nest. It ensures that the foster parents devote their energy to it by ejecting other eggs or chicks from the nest, or trampling on them. The call of the common European cuckoo, Cuculus canorus, pictured here, is popularly held to signal the beginning of spring.

Mark Hamblin/Oxford Scientific Films/BBC Natural History Sound Library. All rights reserved.

Common Hippopotamus

The hippopotamus divides its time between water and land. During the day, its unusually thin outer layer of skin allows moisture to escape too quickly for the animal to remain out of water for very long. Instead of sweat glands, the skin has glands that secrete a thick, reddish fluid impenetrable by the sun’s burning rays; for this reason, hippos have been said to "sweat blood". Hippopotamuses spend the night on land, foraging for the roughly 40 kg (88 lb) of food they consume a day.

Mark Hamblin/Oxford Scientific Films/BBC Natural History Sound Library. All rights reserved.

Secretary Bird

The secretary bird, a bird of prey found in open areas and savannah regions south of the Sahara desert, feeds primarily on insects, rodents, and snakes. Although the secretary bird is an excellent flier, it spends most of its time on the ground.

Stan Osolinski/Oxford Scientific Films/BBC Natural History Sound Library. All rights reserved.

Giant Anteater

Anteaters are native to Central and South America, inhabiting both forest and open-plain regions. The giant anteater, above, is the largest of the species, weighing up to 23 kg (50 lb). The animal is well adapted to hunt for insects, its sole source of food, because of its long front claws and sticky tongue, which can extend to 60 cm (24 in).

Miriam Austerman/Animals Animals/Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved.

Common Puffin

The common puffin, which ranges from the north-western coast of Greenland to Maine, United States, and along the northern coast of Europe, spends most of the year at sea, returning to land only to breed and rear its young. Skilled fliers and fishers, puffins "fly" underwater to catch fish. Their webbed feet are only used to swim at the surface.

Kenneth Day/Oxford Scientific Films/BBC Natural History Sound Library. All rights reserved.

Humpback Whales

Humpback and Northern Right Whales

Virtual Whales

Whales are classified into two groups—toothed whales, such as dolphins and sperm whales, and baleen whales, such as blue or humpback, above. Baleen whales have baleen plates hanging from their upper jaws that allow them to filter plankton out of the tons of water they take into their mouths. Plankton, tiny organisms that live in water, are the only food source of baleen whales.

James D. Watt/Animals Animals/Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved.

Broad-Tailed Hummingbird

This broad-tailed hummingbird, Selasphorus platycercus, hovers alongside a honeysuckle flower, creating its characteristic humming sound with its wings. The specialized skeletal structure of the hummingbird, shared only by its relative the swift, allows its wings to twist. Able to produce 22 to 78 of these wing movements per second, the bird can hover forwards and backwards while it drinks nectar from a flower. Hummingbirds belong to the Trochilidae family of birds, which contains the smallest birds in the world.

Wendy Shattil-Bob Rozinski/Tom Stack and Associates/Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved.

Great Northern Diver (Common Loon)

Awkward on land, the common loon, Gavia immer, belongs to a family of highly specialized divers. By inflating or deflating their lungs and air sacs, loons can make themselves more or less buoyant in the water. They can stay under water for several minutes at a time, diving to a depth of up to 80 m (265 ft). Usually, however, they use their webbed feet to move quickly through shallower waters in pursuit of the fish, crustaceans, and amphibians they commonly prey upon. Chicks are able to dive less than 24 hours after hatching.

George Reszeter/Oxford Scientific Films/Library of Natural Sounds, Cornell Laboratory of Ornithology. All rights reserved.

Tasmanian Devil

Tasmanian Devil (Sarcophilus harrisir)

The Tasmanian devil, exterminated on the Australian mainland, is now found only on the island of Tasmania. A carnivorous marsupial, the Tasmanian devil is capable of completely consuming birds and small- to medium-sized mammals, including all the bones.

Tom McHugh/Photo Researchers, Inc./BBC Natural History Sound Library. All rights reserved.

Mammalian Limb Structure

A common mammalian skeletal structure is modified for each animal’s particular needs. Here, the bones of the forelimb are adapted to each creature’s particular mode of locomotion. From left, the elephant’s immense weight requires a sturdy support to carry it. In contrast, a bat’s wing stretches over a framework of thin, elongated finger bones. The forearms of aquatic mammals such as porpoises and whales form flippers, and the gibbon uses its jointed, flexible digits to grasp and swing through trees.

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