Populations Of Some African Migratory Mammals - Wildebeest, Antelope Species - Falling Rapidly

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As the rain begins to fall on Tanzania's Tarangire National Park, thousands of zebra, wildebeest and giraffe will begin one of the world's greatest migrations. But many of the herds trampling across the grass at the foot of the Rift Valley highlands are falling in number - and scientists do not know why. To find out, they are using a new 'photo-fit' system that can recognise individual animals by their unique skin patterns, which are as distinct as a human fingerprint.

The park, dotted with muddy water holes and ancient baobab and acacia trees, has the highest diversity of migratory hoofed mammal (ungulate) species in the world. The animals move out of the park as the wet season begins, in search of new feeding and calving grounds. They will make the return dry season journey in June, to take advantage of the permanent water of the Tarangire river.

Numbers of wildebeest have fallen from 50,000 to 6,000 in the past 20 years, and numbers of antelope species, such as hartebeest and oryx, have declined by 90 and 95 per cent respectively. Confusingly some species - zebra, giraffe, gazelle and buffalo - have remained relatively stable. To understand such contrasting fortunes, scientists from America's Dartmouth and Utah universities are working to determine whether habitat loss, changed food sources, or hunting - or a combination of all - is responsible.

Traditionally animals have been tracked by being captured and tagged, but that is 'expensive and invasive', says Dartmouth's Doug Bolger. The aerial counts conducted every few years by the Tanzanian authorities don't provide comprehensive data. So the scientists have turned to computer-assisted photo identification - the first time the method has been used on such a large scale. 'This new technology allows us to get the best handle on what the population is doing,' Bolger says. 'Is it increasing, declining, is our response sufficient to offset mortality, is high mortality happening in or outside the park, and what should management do?'

EDIT

http://www.guardian.co.uk/environment/2008/nov/30/wildlife-conservation-africa