【lip eroticism】

Wombats are lip eroticismbiting butts when they're ready to make love.

That's what researchers from Australia's University of Queensland have found in a study, published in the journal Reproduction, Fertility and Development, looking at behavioural indicators of the southern hairy-nosed wombat when breeding.

Southern-hairy nosed wombats don't breed well under captivity, and they are a species which is currently under threat.

Researchers observed the wombats using infrared cameras, as the marsupials are predominantly nocturnal. There they found the female pacing around, possibly related to its desire to find a suitable mate.

"Female wombats in the wild have been found to move around more than the males so it is possible that she goes out looking for potential mates in anticipation for breeding," Tamara Keeley, one of the authors of the study, explained to Mashable via email.

What's more, its urination patterns changed -- less volume, more concentrated -- which could be linked to hormonal changes in the body. And, as mentioned, the females were found to be biting the male's rump, at a time when he tries to mate her.

"It is possible that this biting behaviour is in response to an increased amount of attention by the male, a lack of interest in that particular male, or a means of trying to challenge him before mating to see if she deems him a suitable mate," Keeley added.

The wombat isn't alone in its odd mating habits. Increased aggression, like butt biting, is a behavioural trait that's found in other animals. Depending on the species, it's linked to pair incompatibility or as a means to challenge the male. 

Scientists are still trying to understand the reproductive biology of the wombat, and behaviour is one way they can gain more knowledge. Changes in urination, increased pacing, and erm, butt biting, could be all useful indicators for when they're looking to breed.

"In some species, but not the wombat, females show behaviour signs associated with being in oestrus (receptive to the male)," Keeley said.

"In wombats we were looking for any changes in any behaviour that might be linked to her reproductive status. Knowing when a female will be receptive to a male will help us better manage the animal and hopefully increase breeding success."