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| April 2004 |
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Refining our vulture cultureBy Dr Gerhard H VerdoornSouthern Africans are relatively well informed about vultures, but there's much more to know about these lofty scavengers, their sociable ways and the dangers they face..High-flying decedents of hawks and storks
These tough creatures, which can survive temperatures as low as minus 57 degrees centigrade, evolved from two different lines. The African species, accipitrid or raptorious vultures, are descendants of hawks which developed into specialist scavengers that learnt the art of scavenging without having to expend energy to hunt live prey. In North and South America the cathartid or ciconid vultures evolved through convergent evolution to look and behave like real vultures, whereas their ancestors are in fact storks. In Africa, Europe and Asia there are 16 vulture species, 11 of which are found in Africa. The different African vulture speciesThe archetypal vulture is the Cape Griffon (also called the Cape Vulture or the Cape Griffon Vulture) Gyps coprotheres. These birds, endemic in southern Africa, are obligate scavengers, which means they are unable to kill their own prey as eagles or hawks do. They have large bodies with long naked necks and smallish heads, allowing them to delve deep inside animal carcasses. Intestines and soft tissue make up the bulk of their diet. Three other griffon vultures are found in Africa - the Eurasian Griffon Gyps fulvus, Rüppell's Griffon Gyps rueppellii, and the African White-backed Griffon Gyps africanus. These griffon vultures are very closely related to each other and interbreeding between Rüppell's Griffon and the Cape Griffon has been recorded in South Africa. There is strong phylogenetic evidence that Cape Griffons have interbred with African White-backed Griffons in Namibia. Although this is genetically unsubstantiated it allows for the belief that the griffon vultures are barely yet a species, and may only be remnant representatives of a super-species that once inhabited the Palaearctic region of the world.
The specialist feeders are the Bearded Vulture Gypaetus barbatus and the Palmnut Vulture Gypohierax angolensis. Bearded Vultures inhabit mountainous heights, from where they traverse the land in search of any large bones that have not been consumed by mammalian predators or other vulture species. The Bearded Vultures carry off these bones using their feet. They then fly to a high-altitude rocky outcrop, where they drop the bones smashing them into edible splinters. The Bearded Vulture is distantly related to the Egyptian Vulture Neophron percnopterus. There are two sub-species of Neophron percnopterus. The Indian sub-species N. p. ginginianus is very common, while the African sub-species N. p. percnopterus is extremely sparsely distributed throughout Africa, the Middle East, and Europe - with the exception of Spain where it is fairly common. This sub-species, commonly known as Pharaoh's Chicken, is so rare in South Africa as to be 'national news' when spotted. It was last recorded breeding in 1926 and since then the nimble little vulture has not bred at all. The Palmnut Vulture Gypohyrax angolensis is highly unusual, although it is a scavenger like other vulture species, it feeds largely on the husks of the oily palm tree fruit, and it also catches fish and other aquatic animals like crabs. Some schools of thought place it firmly with the eagles, but the morphology of the bird is that of a true vulture. Vultures can specialise like other animals so there is no reason why a vulture cannot become an omnivore. The Palmnut Vulture is not only an atypical vulture, it is also an extraordinarily beautiful bird with a snow-white plumage and red face. During the breeding season they develop a golden wash on the upper wing due to their habit of nesting in the fronds of the palm trees. Vulture feeding culture
Vultures, especially the griffon types, are highly sociable creatures. Griffons, such as our own Cape Griffon, live in colonies of between a few pairs to hundreds of pairs. Their feeding is a sociable event, with masses of birds gathering to share a carcass. With their powerful beaks the Cape Griffons are able to consume vast quantities of meat within minutes. Due to the pressures of so many birds trying to feed, the vultures gobble down chunks of flesh and can fill a crop with more than one and half a kilograms of meat in four to five minutes. A good feed such as this will last a vulture at least four days before the call of an empty crop sends it out again. Not all vultures can grab the spoils like the griffons do and the more wary Hooded Vulture will patiently wait on the outskirts of the feeding frenzy for another vulture to drop a piece of meat, then stoop on the morsel with great satisfaction. After years of working with vultures in captivity and observing them in the wild I came to the conclusion that food is everything to a vulture. Most of my captive birds, that had been rendered flightless by powerlines, ate food whenever it was offered, irrespective of their crop contents. One particular fellow, Uri, an African Whitebacked Griffon ate until his oesophagus was full and meat was cluttering up his beak. Monster, a Cape Griffon, finished an ox liver of nearly two kilograms in a bare 17 seconds! What they wouldn't eat though was anything cooked or grilled; it had to be raw. Fresh meat was their preference and horsemeat was the favourite. After a few days of starving they would certainly not turn a beak away from cow or kudu meat, but anything small like a road-kill hare was pushing it a bit too far. It would be logical to assume that vultures would eat more during the cold winter months, but surprisingly, the opposite seems to be true, and I have been unable fathom the rationale behind this. Cohabiting with vulturesSouth Africans are fairly well informed about vultures due to the Vulture Study Group of the Endangered Wildlife Trust's 30-year drive to popularise the birds amongst the general public. Many farmers are in full support of vulture conservation and operate vulture restaurants, where these scavengers can find a crop full of good meat. Vulture restaurants also serve another purpose in offering nature enthusiasts an insight into the lives of these birds at close hand. Many such sites develop their own micro-ecosystems with small birds, reptiles, nocturnal scavengers and a host of insects that live on the offerings of mankind. Eco-tourism is also developing around vulture restaurants bringing some direct economic value to landowners. Despite this relatively high degree of vulture awareness there are still many fatal hazards for vultures. Powerlines often electrocute the large birds when they perch on pylons, while conductors in the flight path of a vulture may fracture a wing, leaving the magnificent creature grounded and helpless. And the greatest threat to vultures across Africa remains the destruction of their habitat, which still continues apace. The vast savannahs, where once the great trees were festooned with the nests of African White-backed Griffons, now produce cash crops or lie fallow due to overgrazing and wood harvesting. No trees mean no perches and no nest for the vultures.
The future of vultures in South Africa lies in the hands of people. It is up to us to ensure that they do not disappear. More information: Dr Gerhard H Verdoorn,
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Flight and a ferocious beak are what make the vulture such a spectacular
bird. The highest-flying bird on record is a species of vulture called the
Rüppell's Griffon, once spotted at an altitude of 11,700 metres in the skies of
West Africa during the 1960s. In South Africa's Magaliesberg mountains another
of the vulture species, the Cape Griffons, often venture into the head of
cumulonimbus clouds, possibly as high as 8,000 metres above sea level.
The king vulture, of which the Lappet-faced Vulture
Torgos tracheliotus is
the dominant southern African representative, is a massive beast with a very
powerful beak that aids the bird in opening up the carcasses of fallen animals.
Its smaller cousin, the White-headed Vulture Trigonoceps occipitalis, is the
most colourful of the African vultures. It is the only vulture species that
clearly shows sexual dimorphism in the plumage. In White-headed Vulture females
the secondary flight feathers are white, while in the males they are black.
Less typical is the Hooded Vulture,
Necrosyrtes monachus, which is a timid
little creature with a slender beak. It picks at the last remnants of the animal
carcass once the larger vultures have taken their fill. It lives commensally
with humankind in central and western Africa, where it often feeds on human
faeces and lion droppings that carry undigested meat.
A vulture feeding frenzy is one of nature's most entertaining events.
Vultures arrive from far and wide to compete for a carcass, and this usually
goes hand in hand with serious disputes about the spoils. The larger birds like
Lappet-faced Vultures and Cape Griffons usually dominate the fights, but a good
number of African White-backed Griffons will also be covering a carcass, to the
extent that not even the Lappet-faced Vulture can break into the feeding ranks.
Misuse of pesticides spells disaster for vultures. Lacing carcasses to kill
predators such as jackals, large cats, smaller felids and stray dogs has
resulted in the total demise of vultures in many parts of southern Africa.
Pesticides, such as the organophosphates used against blowfly on small stock,
have killed many vultures, although these products were not intended to harm
birds. Although it is assumed that people are properly informed about the
effects of commercial poisons on wildlife, some individuals may still lace
carcasses with strychnine, carbamates and organophosphates to kill a single
problem animal.