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koala sounds

2

Koala Fieldwork: Helping Hands

Bill is studying wild koalas on St. Bees island off the coast of Australia. Read his previous post, Koalas Get High-tech Support.

It is not always easy for me to convince people that what we are doing is hard work. Our island site is warm and pleasant at this time of year, surrounded by beautiful ocean and inhabited by wonderful koalas. Fortunately, I am having many visitors to my study site, which means I have many more hands on deck, which means we can do even more!

Last month it was Geoff Pye, D.V.M., and Brian Opitz from the San Diego Zoo who helped with catching, collaring, and (most importantly) taking X rays of all the koalas. This month I had Jen and Jen from the San Diego Zoo and the San Diego Zoo Institute for Conservation Research on board, and we worked just as hard. Jen Tobey is a specialist studying the sounds koalas make (see her post Koala Field Project: Meet Jackaroo); Jen Roesler is a keeper at the Zoo who is also an expert in handling koalas, so I expected big things from this pair.

Professor Paul Roe from Queensland University of Technology, who has designed and built the sensor network that eavesdrops on our koalas, and Ben Charlton, an expert in animal communication who has recently turned his skilled hands to koalas, joined us on St. Bees. Rounding out the team was Dr. Sean FitzGibbon, an expert in koala ecology, capture, and handling, with whom I spend a lot of my time in the field.

Our target for this trip was to record the bellows of as many male koalas as we could find so that we could compare the features of each male’s bellows to his size, age, and behavior. We had three microphones and spent every night sitting under the trees of the koalas or running through the bush following their bellows. By day, we tracked the animals, checked on their position so that we knew where to go at night, and caught any new animals that we hadn’t found. We removed the GPS collars that we had deployed in September and also removed some standard vhf collars from animals that we are not going to follow this summer. We were pushed for time, so we even went catching at night, which made for extra-long days.

Luckily, we found several of the females we had caught in September that now had joeys on their backs (many of these were still in the pouch on our last trip). Little Pickle is now a fully fledged mother, and she resides up near Elizabeth, the oldest mother we are tracking. Both of these koalas are raising healthy and good-looking babies this year: Pickle’s baby is named Onion (not my choice of name), and Elizabeth is raising baby number nine, Ginger. We also found some new males; we managed to record the bellows from two of them (Eddie and Jeremy).

It was an exciting and tiring trip, with everyone’s sleep routine totally wrecked by the end. We recorded more koalas that I thought we would, we recovered all the collars we needed to (including Leaper’s, who had crossed the island!) and we even saw two males fighting one afternoon.

We are now starting to put the pieces of the koala–bellowing jigsaw puzzle together. We know that not all the males bellow all the time, but we are not 100-percent sure what makes them decide when it is their turn. We also found bellowing to be concentrated in parts of the island and absent elsewhere, making us wonder whether the males really call to attract the females or whether the females attract the males, who then bellow.

I am sure that as we plan our next trip, we are a step closer to understanding this interesting behavior in koalas; but in the meantime, I am catching up on sleep. Luckily for me, unlike my visitors from the Zoo and the Institute for Conservation Research, I didn’t have an 18-hour plane flight back to San Diego to look forward to when I returned from the island. There are some advantages to living close to your study animals!

Bill Ellis is the Clarke Endowed Postdoctoral Researcher for the San Diego Zoo Institute for Conservation.

6

Koalas of St. Bees Use Cell Phones

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:

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.