Koalas by Day, Koalas by Night!
Posted at 9:21 am August 3, 2006 by Bill Ellis
Hello again from St. Bees Island, Australia, where the rain has kept coming, the koalas have been busy, and the whales have been jumping in the channel! Yes, as part of their annual migration up our East Coast, many humpback whales have been spotted by the koala tracking teams in the last two weeks. However, it's the koalas that kept us most interested.
Once again I led an Earthwatch Expedition to St. Bees Island (July 13 to 24), with volunteers from as far away as Florida and Washington State, and plenty of places in between. We even had a New Zealander on the trip, and she was very adept at climbing the hills of St. Bees Island!
This trip, I set out to ask some very simple but interesting questions that are related to the work that Fred Bercovitch and Jen Tobey (both of the Behavioral Biology Division of CRES) will be focussed on later this year. These questions included whether koalas changed trees during the day time and how far they would go to find a food tree at night.
So, with 10 volunteers, 20 radio-collared koalas and 2 radio recievers, we set out to track the koalas morning, afternoon, and night! This gave us some data on the occurence of tree changes during the day and let us break down the movement of koalas into several periods.
Interestingly, koalas moved from one tree to another during the day on about one-quarter of all observations. Not all the animals moved and it's too early to tell whether it is mostly males, females, or young koalas, but we have an interesting base to start working from to find out why the koalas would change trees during the day. Two tracking teams actually saw koalas walking across the ground during their tracking work, so they had a real treat!
The preliminary data from this trip suggest that there could be a difference in the distance koalas move when going from a day (roosting?) tree to night (feeding?) trees compared to when they move from a night tree to a day tree, but it will be a few more trips before any of this will become clear. And then, of course, there are seasonal (and other) effects that may influence the patterns we see.
As part of our tracking, we found several new koalas, which are now named " Hurricane" and " Indigo." (A koala named Digger is pictured above.) Hurricane is a 20.3 pound (9.2 kilogram) male, quite large for our site, so I will be interested to see what he does come mating season. Quite a few males were bellowing during the trip, something that I'm sure Jen Tobey will be keen to follow up on soon! (See Jen's blog, Motorcycles and Koalas.) Indigo is an 11-pound (5-kilogram) female, but she had no pouch or back young, so maybe this will be her first season?
We had some pretty wild weather, so the boat trip from the island was quite " exciting," to say the least. Although a fair bit of equipment became airborne from time to time, nothing was broken and we all got back safely.
Once again, I was sad to say goodbye to my volunteers; they just learn all the skills and become proficient koala trackers and I have to send them back to their " real" jobs! I think I will miss this crew most for their cooking; we were treated to some traditional American delicacies. The one I liked best was " cobbler" (apparently it's a Southern treat)!
Dr. Bill Ellis is a Conservation Research Postdoctoral Fellow for CRES. Here's more information about his koala project.
Read Bill's previous blog, Welcome Rain for Koalas of St. Bees Island.
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August 3rd, 2006 at 4:06 pm
Had no idea that koalas change trees! At what times of day are they most active? This is very interesting & I want to learn more. Do their activity levels vary seasonally? At SDZ I usually see the koalas around 10:30 a.m. or so, and they seemed to be more active in May & June. I don't know if that was a coincidence. Thanks for the information!
August 6th, 2006 at 1:31 am
Hi Susan,
Yes, in some areas of Queensland, koalas use 9 or more trees per day. We have yet to work out exactly how many they use on any day at St. Bees, but we are working on it. Their ranging patterns do not seem to change substantially size-wise between seasons, but again there are many variables that we need to consider (age, reproductive status, etc.) so there is plenty of work still to be done. What we do know is that koalas on the island (and in other areas) use some species of trees to sit in during the day, but move into food trees in the afternoon or evening to feed.
Regards,
Bill
August 7th, 2006 at 7:51 am
It it true that they are literally " stoned" and therefore you can just pick them up, collar them and then put them back before they realize it? Thanks for the blogs, I am thoroughly enjoying them.
August 14th, 2006 at 4:00 pm
Hi Stacy,
I am afraid not! The koala has a low-energy diet which may account in some part for its apparent low-activity lifestyle. However, when you follow them around at night - as we do - you get a very different picture of their activity.
Regards,
Bill