Washington, Nov 4 : When it comes to settling disputes over access to fertile females, antelopes click their knees to ward off the competition, according to a new study.
The study, conducted on eland antelopes, has revealed the dominance displays used by males to settle disputes over access to fertile females, without resorting to genuine violence.
Led by Jakob Bro-Jorgensen from the Zoological Society of London and Torben Dabelsteen from the University of Copenhagen, researchers studied antelopes within a 400km2 area of Kenya.
They discovered that the males (bulls) use some signals to make competitors aware of their fighting ability, based on three different factors, body size, age and aggression.
"Rivals often use signals to broadcast their fighting ability and thereby settle conflicts without incurring the high costs associated with actual fighting," said Bro-Jorgensen,
The males use the knee clicks, which are shown to be a reliable indicator of body size. The researchers found that the size of a bull's dewlap is related to age.
The authors said: "Age is a good proxy for fighting experience and may also demonstrate that a bull has 'nothing to lose' and will therefore be a more risk-prone and dangerous adversary".
Another underlying variable is hair darkness, which mainly reflects androgen-related aggressiveness.
The scientist claimed that such indicators serve the useful purpose of facilitating assessment by a bull's rivals and avoiding wasteful conflict.
It is believed that the antelopes' knee clicks, which can be heard several hundred metres away, are produced by a tendon slipping over one of the leg bones, which could explain why they correlate with body size,
"The tendon in this case behaves like a string being plucked, and the frequency of the sound from a string correlates negatively with both its length and diameter. Thus, most importantly, depth of the sound is predicted to increase with skeletal measures," said the authors.
The study is published in the open access journal BMC Biology.