What do motorcycles and koalas have in common? They’re both very noisy! If you have never heard a koala before you might be quite surprised by the sounds they produce. The most common vocalization is called a ” bellow.” A bellow sounds like a motorcycle revving or, if you ask a bunch of 8th graders, like someone belching and making other rude noises! Both males and females will bellow, although they sound a little bit different. A bellow is a long, loud call that travels quite far.

The purpose of koala bellows is not clearly understood. Could this be for mate attraction, males calling females to their location, or could it be males warning other males that they are nearby? This is a question we are trying to answer with our koala colony at the San Diego Zoo and in our field project in Australia.

We start by examining the structure of the male bellows to see if they reveal the identity of the caller. For example, when a male koala bellows is it really saying to other koalas ” Hi, my name is Tickera and I am 19 inches tall, 15.8 pounds, and 10 years old”? How do we figure this out? Is there a koala interpreter on staff? Actually, what I use is a computer program that visually shows me the profile of a call. These profiles are called sonograms (see picture of Tickera’s bellows sonogram above) and from them I can measure the duration of the call, the frequencies, and amplitude. I can then compare all of these measures between the different calls of each male in our colony. Any differences or similarities can then be linked to age or weight or size or outside factors like time of year.

We have learned that male bellows are longer in the non-breeding (fall) compared to the breeding season (spring). The number of bellows is about four times more frequent in the breeding season. This means that if you happen to wander past the koalas this time of year, you are more likely to hear a bellow live and in person. We think that the frequency of the calls varies between individuals, but are still examining this, as well as figuring out the ” bellow identity” for each male to see how different they are.

Jennifer Tobey is a Research Fellow in the Behavioral Biology Division of CRES.

Read Jennifer’s previous blog, Smelly Koalas.

Posted in Conservation, Default, General | Link to this post

You can follow any responses to this entry through the RSS 2.0 feed. Scroll to the end to leave a comment. Pinging is not allowed.