You are the alpha male, the top dog, the grand kahuna. A young upstart is trying to muscle his way onto your turf and compete for your women. Your solution – click your knees loudly at him. It seems like a strange strategy. For humans, a clicking knee would hardly be a sign of strength but it’s all part of the bizarre communications of the world’s largest antelope – the eland.
Elands bulls have a strict pecking order that determines their access to females in the herd. On the few occasions when they fight, they hardly ever use their dangerous horns and hooves, preferring instead to prove their strength through neck-wrestling. Even these grapples are a rarity; most eland conflicts are settled without violence through a series of ritual signals.
These signals include the bizarre knee-clicks which the bulls make with their front legs while walking. They sound like castanets and can be heard hundreds of metres away (listen to a WAV file). Predators could obviously use these distinctive noises to home in on eland males, so what purpose could they serve that compensates for this risk?
According to Jakob Bro-Jorgensen from the University of Jyvaskyla and Torben Dabelsteen from the University of Copenhagen, the clicks are a message to other males and their frequencies provide an honest and accurate measure of the individual’s size and fighting ability.
Bro-Jorgenson and Dabelsteen spent several months in Kenya studying the signals used by elands. Armed with little more than a microphone and a camera, they meticulously recorded information on 48 males and followed up on 14 of these a year later to see if they had changed at all. They found that the frequency of an eland’s knee-clicks reflects its size. The bigger the animal, the lower the frequency of its clicks and the deeper the resulting sound.