Som Ale and Joel Brown of University of Illinois-Chicago have come up with a new method to monitor the snow leopard (Uncia uncia) by observing the behaviour of its usual prey, the Himalayan tahr (Hemitragus jemlahicus). Michael Hopkin in news@nature.com writes:

The researchers 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.

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.