Male platypuses and echidnas both secrete from a spur in their hind leg. In platypuses the spur injects venom into competitors causing pain and swelling but the purpose of the echidna spur and secreted substance has been unclear.

"A waxy secretion is produced around the base on the echidna spur, and we have shown that it is not venomous but is used for communicating during breeding," said Professor Kathy Belov, lead author of the study published in PLOS One today.

Professor Belov is from the University's Faculty of Veterinary Science.

Monotremes are egg-laying mammals and Australia and New Guinea are the only places in the world that have living species. Australia is home to the platypus and short- beaked echidna.