Vulture, Cape

views updated

Vulture, Cape

Gyps coprotheres

phylum: Chordata

class: Aves

order: Falconiformes

family: Accipitridae

status: Vulnerable, IUCN

range: Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland, Zimbabwe

Description and biology

The Cape vulture, also called the Cape griffon, is an Old World vulture that belongs to the same family as hawks and eagles. It has a long, bare neck and a specially shaped tongue that allows it to feed inside the carcasses (dead bodies) of sheep, cattle, pigs, goats, and horses. The bird roosts (rests or sleeps) with other vultures in colonies on cliffs. Unlike most birds of prey, the Cape vulture does not use thermals (rising warm air currents) to fly. Instead, it uses the swift air currents that exist around its roosting sites. The vulture used to eat the carcasses of large migratory mammals. Now, it must depend on dead livestock for food.

Cape vultures begin to build their nests in early March. The nests are made of grass with a rim of feathers and sticks.

They are usually built on south-facing cliffs that have ledges. Once constructed, the nests are often used for several years.

A female Cape vulture lays a clutch (eggs produced at one time) of only one egg between April and July. Once the chick hatches, it is fed the meat and, sometimes, bones from animal carcasses. Both eggs and newborn chicks face several natural threats. Clouds that settle on south-facing cliffs can often cause them to freeze to death. They also are preyed upon by black eagles and white-necked ravens.

Habitat and current distribution

The Cape vulture is found only in the southern African countries of South Africa, Lesotho, Swaziland, Botswana, Namibia, Zimbabwe, and Mozambique. It breeds primarily in two areas. An estimated 2,300 breeding pairs are found in Transvaal (northeastern province in South Africa) and in eastern Botswana. Another group of about 950 breeding pairs are located in the Transkei (self-governing republic in South Africa), Natal (eastern province in South Africa) and Lesotho.

Because Cape vultures generally live and forage for food away from their breeding areas, their range extends almost over all of southern Africa. Biologists (people who study living organisms) have estimated that about 12,000 Cape vultures currently exist. The birds prefer to inhabit open spaces. They forage over grassland, desert, and other areas with sparse vegetation.

History and conservation measures

In the nineteenth century, the Cape vulture was seen in high numbers in southern Africa. It began to decline in the early twentieth century, though, when a disease wiped out many cattle in the region, robbing the bird of its food source. A drop in the number of cattle due to disease and other factors between the years 1950 and 1971 again hurt the Cape vulture population.

Today, the main threat facing the Cape vulture is not food quantity but food quality. Cape vulture chicks require calcium in their diets to prevent osteodystrophy (pronounced os-tee- o-DIS-trow-fee), a disease that causes their bones to become weak and deformed. When large mammals kill and feed upon animals, they often crush their bones in the process. Vultures then feed on the remaining carcass, and the chicks are fed meat that has bone flakes (calcium) mixed in it. Since the number of large mammals in southern Africa has declined, however, vulture chicks have suffered because they have not been able to eat enough meat mixed with bone flakes.

Cape vultures are also threatened by humans who disturb their breeding grounds and who poison them. Many farmers and ranchers in the bird's range believe it attacks sheep and then transmits to other animals any disease the sheep might carry. To prevent this, these farmers and ranchers often put out poisoned carcasses for the vultures to feed on, and the birds die as a result.

The belief that Cape vultures normally attack sheep and spread disease is a mistaken one. Conservation groups in southern Africa have tried to stop farmers and ranchers from leaving poisoned carcasses for the birds. Conservationists (people protecting the natural world) have also set up areas where carcasses with crushed bones have been put out for the vultures. This practice has helped reduce the number of vulture chicks suffering from osteodystrophy. The Cape vulture has full legal protection throughout its range.