Vultures - Supreme Scavengers

Along with snakes, spiders, hyenas and sharks, vultures are regarded as the "bad guys" of the animal kingdom. All creatures do, of course, have a role to play in nature and it is only though the subjective and emotive thinking of humans that labels such as "evil", "horrid", "cruel" and "merciless" arise. No animals possess such traits - they are all engaged in a struggle for survival which sees them trying to optimise on feeding and reproductive opportunities within the ecosystems in which they have evolved, and the particular niches that they occupy.

Benign But Persecuted

Even the most cursory examination of the lifestyle of a vulture, reveals it to be a benign and useful creature, but countless individuals have been shot, trapped or poisoned by people over the last hundred years or so. The not infrequent sight of a group of griffons feeding on the carcass of a sheep or a calf, has repeatedly led to the conclusion that these birds are predators, when in fact they are dedicated scavengers performing the vital function of removing (recycling) rotting carcasses. Unlike eagles and hawks - which have sharp talons - vultures are not adapted to kill for themselves although there are rare instances of desperate or hungry birds taking small or weak animals.

It is western man who is to blame for the "bad press" and demise of vulture populations, for these useful birds are revered in many other religions and cultures. The Hindu regard vultures as carriers of the human spirit, while the ancient Egyptians depicted them in their hieroglyphics and totems. The introduction of livestock and "ownership" of wild animals (which then became "game") thrust vultures into conflict with farmers and settlers in Europe, North America and Africa, where several species have become endangered.

Icons of Africa

Vultures are as much a part of the African wilderness as giraffe or zebra, and it is always a thrill to see them soaring in the sky above, or jostling with one another at a carcass. Although their somewhat reptilian facial features (not to mention their mostly "messy" feeding habits) eliminates them from any "beautiful bird" line-up, they are majestic on the wing when their power and grace is evident.

Contrary to popular opinion, vultures are not reliant on the left-overs of predator kills, although they will frequently visit the site of a kill and will certainly take food if it is available. Lion and spotted hyena usually hunt and feed after dark and if they do make a kill by day, they are invariably too imposing for the vultures. In reality, the bulk of vulture food comes from mortalites such as old age, diseased or broken limbed-animals and still-born young. When one realises that up to 100 000 wildebeest must die each year in the Serengeti-Mara (for a population of one million to be maintained among an animal that lives for a maximum of ten years) it is plain to see that vultures would survive well enough without lions. In Southern Africa - with its denser woodlands and lower biomass - it may be that vultures gain a greater proportion of their meals from predator leftovers although this has yet to be studied in any detail.

Interestingly, the eight species of vulture in African savannahs are not only able to co-exist, but may actually benefit one another through their different foraging techniques and feeding habits. When vultures are feeding together at a carcass, co-operation is perhaps the last word that might come to mind, as they hiss and stomp on each other to try a get a mouthful of flesh, but closer examination raises this interesting prospect.

First Come, First Served

The White-headed Vulture is the most-lightweight (in relation to its wingspan) of the African vultures and is therefore the most mobile and agile species. Because it is up and about early in the day, it is frequently the first to locate a carcass and often enjoys the first choice soft parts but it seemingly prefers sinew and hide, and cannot reach this until a large flock of griffon vultures have dismembered the body. Interestingly, the White-headed Vulture has striking black and white plumage and its decent to a carcass will be easily noticed by a griffon soaring at a higher altitude (ravens and crows - with their white collars - do likewise in mountainous landscapes).

Guzzling Griffons

Three species conform to the typical image of a vulture - sinuous neck and bald head - and are collectively known as "griffons". Most common is the White-backed Vulture, a tree-nesting species which lives in loose colonies in tall trees along drainage lines or rivers. Several hundred White-backed Vultures may gather at the carcass of an elephant or giraffe, and they usually outnumber all other species by at least three to one.

In East Africa, the impressive Rüppell's Griffon occupies the open savannahs, with the largest population in the Serengeti-Mara. Here, the natural die-off from the enormous migratory wildebeest population provides them with ready sustenance. These heavy birds breed on rock faces in the Gol Mountains and may traverse 200km and back when the wildebeest herds have moved to Kenya's Masai Mara. It has been suggested that the colonial lifestyle of the griffons is similar to that of gannets and other cliff-nesting seabirds, in that it serves as a communication network: birds arriving back at their nests with a full crop let others know that their foraging has been a success and the direction from which they came will be noted. In this way, foraging time for the others is reduced and the chances of finding a meal increased (in Southern Africa the Cape Griffon occupies an equivalent niche to the Rüppell's but is now endangered as it is now largely restricted to agricultural landscapes.)

Many Eyes, Many Mouths

In order to locate carrion, scavenging vultures must employ various tactics. First, they need to be able to soar at heights which afford them great visibility. Second, they need to either fly at an altitude which allows them to detect a stationery object (the carcass) or activity on the ground (other scavengers), or at a higher altitude which allows them to monitor the movements of other vultures and scavengers, and then follow them down to the food. This latter approach widens the net, so to speak, and is used by the griffons which are so heavy that they must anyway make use of the rising thermal currents to stay aloft (they cannot maintain flapping flight). Being gregarious, there is invariably more than one set of griffon eyes scanning the sky below and once one bird drops to investigate, it will be rapidly followed by others.

This is where the trade-off takes place, for once on the ground the griffons challenge and jostle with each other as they compete vigorously for food. The griffons are red meat feeders, thrusting deep inside the carcass with the long featherless necks to feed on soft flesh, in preference to hide, sinew and bone. Depending upon the size of the carcass, most will usually get something to eat (the most aggressive vultures get slower as they fill up!) and it is presumably worth the fight to forage in a group with many eyes.

The King

The Lappet-faced Vulture is the largest of the African vultures with a wingspan of over three metres. It typically arrives at a carcass once the griffons have begun feeding, but is able to dominate the proceeding by lunging out with its enormous bill and outstretched wings - even forcing a couple of dozen griffons to retreat. Interestingly, this is the only vulture with a bill strong enough to open the tough hide of a buffalo or giraffe and proper access for the griffons can only be gained once the Lappet-faced Vulture has dined.

On the Fringe

The Hooded Vulture and Egyptian Vulture are very similar anatomically, with feathered heads and long thin bills. They are too small to compete with the larger vultures, but do well for themselves by keeping to the fringes, snapping up morsels and retrieving marrow from shattered bones. The Hooded Vulture is typical of wetter climates - even occurring in the edge of tropical rainforest - while the Egyptian Vulture prefers arid scrublands.

Winged Specialists

The magnificent Bearded Vulture (Lammergeyer to some) and fish-eagle-like Palmnut Vulture are oddities in terms of habitat and feeding requirements, and only rarely interact with other vulture species. The Bearded Vulture lives in the high mountains where it feeds mostly on marrow and bones, while the Palmnut Vulture is primarily vegetarian and seldom strays far from the Oil Palms from which it gets its favoured diet of palm nuts.

Till Death Do Us Part

Vultures - like many other large, long-lived birds - pair up for life, which, in the case of a Rüppell's Griffon, may be forty or fifty years. Just a single egg is laid each year and the youngster is only just gaining independence when the next breeding cycle begins. In Southern Africa, vultures time their breeding such that their developing young are being raised at the end of the dry season when visibility is greatest due to low vegetation cover, and natural herbivore mortality is highest. The East African vultures may be more flexible in their timing, as the two rainy seasons (the so-called "long rains" and "short rains") in this region have an effect on herbivore breeding and movements.

Where to See Vultures at CCAfrica Properties

Vultures occur in all sizeable protected areas and very often in surrounding areas occupied by pastoralists and subsistence farmers. Five species may be reliably encountered in the wilderness areas of the Serengeti-Mara ecosystem (Tanzania/Kenya), Okavango Delta (Botswana), Zambezi woodlands (Zimbabwe) and Southern Lowveld (South Africa). The dramatically-positioned Ruppell's Griffon breeding colonies in the Gol Mountains may be visited while based at Ngorongoro Crater Lodge in Tanzania, although this is a full day's excursion on rutted tracks and only for the determined or adventurous; the rare Egyptian Vulture is sometimes encountered on the short grass plains at the base of the Gol Mountains.

Great numbers of vultures are present in the Masai Mara National Reserve in Kenya between July and November, and a stay at Kichwa Tembo Masai Mara Tented Camp will provide superb viewing and photographic opportunities. It is on the Mara River that many wildebeest drown in their attempt to cross, that vultures often gather in great numbers, and a similar scenario can be viewed earlier in the year from the Grumeti Serengeti Tented Camp in Tanzania on the fringe of the Grumeti River in the Serengeti.

For more information of African vultures, the authoritative, The Vultures of Africa, by Peter Mundy et al is recommended. The South African edition of this book is now out of print, but the international (Academic Press) edition can be obtained from http://www.amazon.com/ (USA) or http://www.nhbs.com/ (UK), which is a natural history, environment and science bookstore.

Posted: Birds by CC Africa, Date: 21 November 2006