Hello again from St. Bees Island, off the coast of Australia, where it seems the koalas have taken a break from their nightly ritual of bellowing. Not many people actually get to hear a koala bellow in the wild, but our San Diego Zoo Conservation Research team has found a way to do it all day, every day. Actually, koalas call mostly at night, but just in case, we have been listening in 24/7. We have been using mobile phone technology to listen and transmit the sounds from St. Bees to our computers, with some interesting results.
We have a male koala bellow for you to listen to [audio:http://www.sandiegozoo.org/animalbytes/sounds/koala_male_bellow.mp3]

This project began in earnest at the start of the breeding season on St. Bees Island, which is at the start of September. We are very interested to know what is the purpose of the bellows male koalas make during breeding times. It could be a cue for other males to stay away or may be some form of advertising for females, but it turns out that, like a lot of aspects of koala biology, there is plenty to learn about this behavior.

We have placed three solar-powered remote listening stations on St. Bees Island. These microphones record sound onto a mobile smart phone for two minutes, every half hour, throughout the day and night. Once recorded, the sound is transmitted directly to a server in Brisbane and uploaded onto a Web site, managed by our partner in this project, Queensland University of Technology. We can usually analyze each recording within 10 minutes of it being captured, so we have some very up-to-date information on what is going on at St. Bees, even when we are not there.

So far we have found that koalas do indeed do most of their bellowing at night; bellows during the day are very uncommon. We have found that the average length of a call is around 40 seconds, with some lasting up to nearly 2 minutes. Although at first we found more calls occurring around midnight, as the season has progressed this trend has been less apparent, and it seems that the calls change in structure as the season progresses.
We have also been fortunate enough to capture some interactions between males and females, where we have heard both animals vocalizing while they are interacting.

What we will be doing in the coming weeks is downloading the GPS data from all of the radio collars worn by the koalas. This way we will know whether males, or females, move more when we hear the most calls. This should indicate whether males are talking to other males or to females.

Since Christmas, there has been a marked decline in the number of bellows we have heard on the island. This is interesting, because although we know the bellowing is a seasonal phenomenon, no one really is sure what triggers the start or end of it, or how important it is to breeding for koalas. These are the sorts of questions we are trying to answer through our research at St. Bees Island.

We expect that fewer and fewer bellows will be heard as the koala breeding season in Australia comes to an end during March. Fortunately for visitors to the San Diego Zoo, this signals the start of the Northern Hemisphere breeding season, so although there might be few calls from St. Bees, there are likely to be plenty coming from the koalas at San Diego!

Bill Ellis is a Conservation Research postdoctoral fellow for the San Diego Zoo.

Read Bill’s previous blog, Koala Tracking with GPS.

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