Apr 8, 2014

Koalas Change Trees From Day to Night

Give me a home among the gum trees, one to snooze in during the day, and a different one at night to eat.

That's the preference of koalas, according to a new study that examines the iconic Australian animal's behavior and feeding patterns published in the latest issue of CSIRO journal Wildlife Research.

The discovery has implications for koala conservation, says study lead author Karen Marsh of the Australian National University.

"At the moment a koala habitat is based on the trees people find koalas in during the day, but those aren't necessarily the trees they want to eat, and so we need a broader habitat definition," said Marsh.

Although koalas are a popular species for study, very little is known about their behavior and feeding patterns, especially at night.

"A lot of people have researched what trees koalas prefer from a non-feeding perspective, but there's an assumption that if you see a koala in a tree, then they probably eat it," said Marsh.

"Just by looking at koalas in trees, without taking into account how much they eat from those trees, means we're missing the larger picture of what else they use these trees for.

"We wanted to know what makes koalas interested in one type of eucalypt rather than another."

Bugging koalas

To investigate what koalas get up to day and night, Marsh and colleagues attached microphones to eight animals in a bush reserve on Victoria's Phillip Island.

They used audio and radio telemetry to track koala movements and continuously monitor their activities for 14 days, to determine their feeding patterns and social interactions.

"We recorded hundreds of hours of data," said co-author Ben Moore of the University of Western Sydney.

"We were able to determine which trees they were in at different times, and could also hear them munching on leaves. This allowed us to record the types of trees they visited, as well as when, how often and for how long they feed."

The researchers were then able to examine the trees being used by the koalas, and analyse the nutritional composition of the leaves.

Koala favorites


They found the trees koalas preferred to sit in, didn't necessarily correspond to what they preferred eating.

Individual koalas varied in how many trees they visited, how many meals they ate and how long they spent feeding during each 24-hour period.

They liked to relax in blue gums (Eucalyptus globulus) during the day, but fed mainly at night, with a general preference for Manner gums (Eucalyptus viminalis).

"We don't really know how koalas choose trees, but they all seem to prefer leaves with more protein and less toxins, and spend much longer feeding in those trees," said Marsh.

"Koalas eat very different amounts from each tree they visit and that is highly dependent on the nutritional value of the leaves.

"Each tree can have very different levels of proteins and toxins compared to the tree next to it regardless of the species, which can have a big impact on how much the koalas eat."

The researchers also found koalas had a very strong preference for sitting in large trees with more shade during the day.

Read more at Discovery News

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