Vulture culture

0

Vultures may not be to everybody’s taste, but these large scavenging raptors have some remarkable talents and are vital to the stability of Africa’s natural environment. Mike Unwin explains why

HR-GettyImages-113870744We are friends,” chorus the vultures in Walt Disney’s The Jungle Book. “Friends to the bitter end.” Sadly, though, these birds find few friends elsewhere. As with hyenas, their association with death elicits fear and revulsion. This is a great shame, as few creatures are more fascinating – or important.

Vultures are effectively the hyenas of the skies, playing a vital ecological clean-up role by disposing of decomposing carcasses. And they are well equipped for the job: broad wings allow them to soar effortlessly for hours on end; acute eyesight enables them to locate their quarry from miles away; and long necks, powerful bills and potent stomach acids all help them deal with the most putrid carcasses.

When it comes to tracking down the dead or dying, few animals possess a more sensitive radar than vultures. While spiralling above the bush, they are looking not only for carcasses but also for clues in the behaviour of other animals on the ground, such as impala fleeing from wild dogs or hyenas approaching a lion kill. More than anything, they are watching other vultures. Birds dropping to the ground in one area will suck others out of the sky from miles around. This is why hundreds may appear within minutes, apparently from nowhere.

Admittedly, the friendship thing seems a little far-fetched when you watch the hissing, lunging squabbles of vultures at a carcass. In fact, there is a strict pecking order, both among individuals of different and the same species.

At a typical savannah gathering, for instance, the huge and aggressive lappet-faced vulture lords it over other species, using its powerful bill to open up a carcass. Smaller hooded vultures, by contrast, may move in only when the others have moved away, but then use their slimmer, more surgical bills to reach parts of the animal that escaped their larger cousins.

And while the whole idea of feeding from a decomposing body may seem a little squalid to those of a delicate disposition, vultures are far from filthy creatures. The naked heads of most species is an adaptation that allows them to poke around in the gore without fouling their feathers. And they are fastidiously clean birds, visiting water daily to drink and bathe.

Vultures live for a long time – sometimes up to 50 years. Pairs form lifelong bonds, producing one or, in some species, two chicks per year. Incubation, shared by both parents, takes 54 to 58 days. The youngsters fledge after about four months but could remain dependent upon their parents for a full year. Some species nest in tall trees; others on cliff ledges. A few, including cape vultures, form large colonies.

Today vultures need all the friends they can get. Most species are in steep decline across Africa. Direct threats range from power lines to persecution – as many as 86 dead birds have been recorded at a single poisoned carcass put out by farmers for jackals. Meanwhile the disappearance from many regions of game populations and predators is leaving them increasingly short of food.

In former times the birds received rather more respect: Nekhbet, the vulture goddess of ancient Egypt, was revered as a protector of royal children. And in the ancient sky burials of central Asia and parts of India – in which bodies were left out to be consumed by vultures – they enjoyed a sacred status. We can only hope the ‘bitter end’ for these impressive and useful creatures is a while away yet.

a

Who’s who?
All the African species belong to a group known as Old World vultures, which – along with hawks and eagles – form part of the Accipitridae family of birds of prey. They are quite distinct from New World vultures, such as the turkey vulture, which are found only in the Americas and are more closely related to storks. The two groups have acquired many similar traits through convergent evolution. New World vultures, however, track down carcasses by smell rather than eyesight.  The following ten species all occur in Africa:

Lappet-faced vulture (pictured, flying in) (Torgos trachelioto)
Huge species (up to 115cm in body length) that uses its great size to bully smaller species off the kill; found from South Africa to the Middle East in savannah and semi-arid habitats.

Cape vulture (Gyps coprotheres)
Very large; numbers much reduced; breeds on cliffs in mountainous regions of southern Africa but travels widely.

Griffon vulture (Gyps fulvus)
Large vulture of mountainous areas in Eurasia and parts of North Africa but not found south of the Sahara.

White-headed vulture (Trigonoceps occipitalis)
Medium-sized vulture with skull-like head; shy and solitary, often feeding away from carcass.

Hooded vulture (Necrosyrtes monachus)
Small, dark vulture that uses its thin bill to steal smaller scraps; common around villages in West Africa.

White-backed vulture (pictured, on the ground already) (Gyps africanus)
Abundant, medium-sized species identified by the white lower back; hundreds may gather at a large carcass.

Egyptian vulture (Neophron percnopterus)
Small, black-and-white vulture found as far as India and the Mediterranean; usually seen alone or in pairs; joins carcasses after other species have left; uncommon.

Rüppell’s vulture (Gyps rueppellii)
Slightly larger than the white-backed vulture, with which it often gathers; does not occur south of Tanzania.

Bearded vulture (Gypaetus barbatus)
Very large vulture, with narrow wings and feathered head; feeds on bone marrow; found only in the mountains, with a scattered range from Ethiopia to South Africa; rare.

Palm-nut vulture (Gypohierax angolensis)
Smallest Old World vulture (at 60cm); black-and-white colouring; found near coasts and rivers, where it feeds largely on the fruit of the oil palm.

a

Fit for purpose
Vultures have evolved a number of special adaptations for their scavenging lifestyle

Wings They have broad wings, which, in the largest species, may span up to 2.8m.Their low ‘wing-loading’ – the ratio of body weight to wing area – enables them to remain airborne for long periods without flapping and to manoeuvre at low speeds without stalling. For lift, they require thermals – pockets of warm air rising from the sun-heated ground – and move from one thermal to another to survey wide areas easily. In inclement weather vultures may not fly at all.

Ruff The erectile ruff of feathers around a vulture’s neck helps prevent its bare head from losing too much heat when soaring at altitude or roosting in cold conditions.

Head The head of a typical vulture is virtually naked, covered only in fine down. This means that no feathers become soiled when it feeds inside a carcass; it also helps in thermoregulation, allowing a vulture to lose or preserve heat by hiding or exposing its head according to conditions.

Neck A vulture’s long neck allows it to probe deeply into carcasses. It may also be retracted in flight and when roosting to keep the bare head warm.

Eyesight Vultures’ eyes are eight times more powerful than ours, allowing them to see a 6cm object from a height of 1km. Each eye has two lenses: one to scan the landscape and the other to magnify objects.

Stomach Vultures’ stomachs are equipped with powerfully acidic gastric enzymes. These can break down bone inside 24 hours, and contain antibacterial agents that protect the birds from the deadly germs – such as anthrax and botulinum toxin – that may be present in putrid carcasses.

Feet Their flat feet lack the killing grip and lethal talons of other birds of prey, such as eagles. Instead, they have evolved for getting around on the ground and for an easier run-up when taking off.

Bill A vulture’s powerful bill is adapted to tearing through thick flesh. Inside, the tough tongue is covered in small spines that help tear smaller pieces of flesh from hide and bones.

Crop A vulture can cram up to 1.4kg of carrion into its crop – a distensible sack, located in front of its oesophagus. Vultures cannot depend upon finding food daily, so this supply works as a packed lunch. When disturbed, a vulture will empty its crop for a quick take-off and escape.

a

Vulture variations
Three of the species found in Africa differ significantly from the others. They neither look similar to nor behave like typical vultures, and they seldom join the throng at carcasses. Each belongs in a genus all of its own

The veggie vulture
The palm-nut vulture (Gypohierax angolensis) is a strange oxymoron of nature: a vegetarian carnivore. This smallish species, which some taxonomists believe to be more closely related to the African fish eagle, eschews flesh in favour of the tough nut of the raffia palm (Raphia australis). It plucks the fruit with its bill — often hanging upside down in the process — then, clutching the prize in its talons, tears off the husk and eats it. The oil palm (Elaeis guineensis) offers an alternative diet in some areas, as do other fruits such as wild dates. Even veggies have their lapses, however, and the palm-nut vulture will sometimes betray its raptor roots by snatching dead fish — and the occasional live one — from the shore. It will also eat crabs, molluscs and locusts, and has even been known to grab the odd chicken. Palm-nut vultures inhabit coastal and riverine regions throughout sub-Saharan Africa wherever there are stands of raffia or oil palms.

The bone breaker
The bearded vulture, or lammergeier (Gypaetus barbatus), inhabits mountainous regions, generally above 1000m in altitude, where it builds huge nests on remote crags. Notable populations occur in the highlands of Ethiopia, central Kenya and Tanzania, and South Africa’s Drakensberg Mountains. Despite its massive 2.6m wingspan, this vulture has a slender flight profile, with the long wings and diamond-shaped tail more reminiscent of a smaller raptor such as a kite or falcon. Its underparts are a rich rusty-orange, and its fully feathered head sports a dark ‘beard’ below the eyes and bill. Lammergeiers are rare and timid visitors to carcasses. They feed almost exclusively on bone marrow, which they extract from bones by dropping them from a great height to smash them open. It takes young birds seven years to master this art.

The egg cracker
The Egyptian vulture (Neophron percnopterus) is a small, largely solitary species, identified by its black-and-white plumage and yellow face. It is fond of the eggs of large birds, including ostriches and kori bustards, and to get at the contents it will crack open the egg by tossing small stones at the shell. Round stones are preferred, the bird clutching the missile in its bill and flinging it down on the egg with some force, repeating the action until the shell cracks. And as if one trick wasn’t enough, Egyptian vultures in Bulgaria have also been observed using a twig to roll up and gather strands of wool for lining the nest.

a

Vulture hotspots
You can see numerous vulture species in all large conservation areas that still harbour plentiful game. Keep an eye on the skies during the heat of the day and, when the weather is poor, scan the horizon for the birds hunched in treetops. A few smaller reserves, notably in South Africa, maintain ‘vulture restaurants’, where a supply of carcasses from abattoirs and elsewhere is left out to supplement the birds’ natural diet. Remember, whether you like them or not, that vultures are often your best means of tracking down big cats and other predators. Top spots include:

Tanzania & Kenya: Serengeti National Park and the Masai Mara
They follow the great migration, cleaning up what the larger predators leave behind. The annual crossing of the Mara River, when large numbers of wildebeest drown, provides perhaps the continent’s largest vulture feast.

Swaziland: Hlane Royal National Park
This small reserve protects Africa’s southernmost breeding colony of white-backed vultures and receives regular visits from Cape vultures and other species.

South Africa: Drakensberg Mountains
In panoramic mountain reserves such as Giants Castle you can watch Cape vultures and lammergeiers visiting feeding stations.

The Gambia: The coast
Hooded vultures are common visitors to the villages and resorts that crowd the coastline, feeding on human refuse. Look out also for palm-nut vultures in the mangroves and palm groves.

Others:Botswana’s Okavango Delta and Chobe National Park, Zimbabwe’s Hwange National Park, South Africa’s Kruger Park and Zambia’s Luangwa Valley are among other well-known reserves that support substantial vulture populations.

Share.