Published online 10 August 2006 | Nature | doi:10.1038/news060807-12
Endangered cats leave ‘trail of fear’: Snow leopards tracked by monitoring fright of their prey.
The endangered snow leopard has returned to the valleys around Mount Everest, say wildlife researchers working in Nepal. And how do they know it’s back? Because the leopards’ traditional prey are terrified.
Tracking top predators by spotting the fear they instil in their prey could offer a new way to monitor the conservation status of rare animals, says Som Ale of the University of Illinois-Chicago, who came up with the idea. “We can get clues about their whereabouts from the behaviour of their main prey species,” he says.
He and his colleague Joel Brown tracked the elusive snow leopard (Uncia uncia) by observing the behaviour of its usual prey, the Himalayan tahr (Hemitragus jemlahicus), a relative of wild goats.
The leopards, of which there are only around 6,000 left in the wild, had vanished completely from the foothills of Everest after the region was opened up to tourists in the years following the first conquest of the mountain in 1953.
The tahr have had a relatively easy ride since 1976, when Everest and the surrounding area were declared a national park. But since 2000, their population has stopped growing and the number of mothers with young has dwindled, leading some conservationists to suspect that the snow leopard was back.
The problem lay in proving it — spotting the leopards is immensely difficult. “For many conservationists it’s a once-in-a-lifetime event,” Ale says. But the tahr are much better at spotting leopards; after all, their lives can depend on it.
On the look-out
The researchers therefore sought to spot the hallmarks of fear among the previously complacent tahr. Signs include ears standing on end, eyes focused into the distance, and a whistling cry used to communicate danger to other tahr.
Ale and Brown found that the tahr were most vigilant on cliffs and in open forests. And when they checked these habitats, they found droppings and paw-prints from the leopards. Ale presented the results at the meeting of the Ecological Society of America in Memphis, Tennessee.
What’s more, observation of the tahr led to six direct sightings of the leopards, Ale says. Simply watching the tahr will not allow a census of the leopard population. But if it leads to direct leopard visuals it may be valuable in estimating how many leopards are living in the area.
Of course, the plan would not have worked at all but for the fact that the tahr have no other natural predators, meaning that they only get scared of leopards. Not even the local people are a threat. “The people who live there are Sherpas, who are Buddhists,” Ale explains.
That meant that the researchers could get within some 20 metres of the tahr without causing them to flee, says Ale — which was useful for monitoring their behaviour. “And it meant we got really good photos of them,” he adds.