Koala bellows shows size counts

By AAP and AG Staff 29 September 2011
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Male koalas have learned to belt out louder bellows much bigger than an animal of their size.

IF YOU’RE A KOALA, hot for some action and want to prove you’re top gum, you’d better start bluffing, Blinky.

A team of researchers has found the bellowing sound made by male koalas may be used to boast to other koalas about how big they are, the online Journal of Experimental Biology says.

Koalas are generally quiet animals, sleeping for 19 hours a day and eating for three out of the remaining five hours. But during mating season the males become very vocal.

Previous reseach found that many males belt out a bear-like growl to attract females and that these bellows had different frequencies. 

The new research by Dr Benjamin Charlton, from the University of Vienna in Austria, has gone a step further to reveal that koalas with longer vocal tracts produce deeper resonances.

Listen to the sounds of a male koala:

Koala mating call a bluff

Teaming up with researchers at the University of Queensland, Benjamin examined koalas at a sanctuary in Brisbane.

The scientists found koalas were able to make themselves sound as if they were much bigger than they actually were for an animal of their size. The loud bellowing could have driven the evolution of the koalas’ larynxes, the researchers suggest.

“Individuals that could elongate their vocal tracts by lowering the larynx may have gained advantages during sexual competition by sounding larger,” Benjamin said in a statement.

He said it is possible that the koala is one of the few animals to have a descended larynx.