By Anna Salleh for ABC Science Online.
Male fiddler crabs spy on their competitors to work out when a potential female mate is around, Australian researchers have found.
Their findings are reported today in Biology Letters.
"Males will use other males as female detectors," says behavioural ecologist Richard Milner of the Australian National University in Canberra.
"They'll eavesdrop on other males' courtship displays to detect the presence of a female."
Milner carried out the research for his PhD under the supervision of Associate Professor Patricia Backwell and Professor Michael Jennions.