By Dr. Becker
Just as humans don't stretch out on the dining room table or crawl into the fridge at night to sleep, a new study reveals that koalas also don't sleep where they eat.1 Researchers at Australian National University have discovered that koalas prefer to nap during the day in one type of tree, then switch trees at chowtime.
According to lead study author Karen Marsh, this finding may impact future koala conservation efforts.
Koala Conservation Status
According to the IUCN (International Union for the Conservation of Nature) Red List of Threatened Species, the koala is categorized as Least Concern due to its "wide distribution, presumed large population, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category."
However, according to the Australian Koala Foundation (AKF), in April 2012, the Australian Government categorized the koala as Vulnerable, and further, research conducted by the Foundation indicates that the status should be upgraded to Critically Endangered in the South East Queensland Bioregion.
Per the AKF:
"Koalas are in serious decline suffering from the effects of habitat destruction, domestic dog attacks, bushfires and road accidents. The Australian Koala Foundation estimates that there are less than 80,000 Koalas left in the wild, possibly as few as 43,000."
The Foundation asserts that koala habitat is not being protected anywhere in Australia, and apparently, it's not that legislation doesn't exist, but that there isn't the "political will" to adequately enforce existing legislation. I hope my Australian followers will push for appropriate legislation that protects this vulnerable species now, before conservation efforts are attempted too late, as was the case with the black rhino.
Researchers Set Out to Discover Which Trees Koalas Prefer for Different Activities, and Why They Choose Them
According to Australian National University lead study author Marsh, the current understanding of koala habitats is based on where the animals are found sleeping during the day. However, if those aren't the same trees koalas like to eat from, then clearly a more accurate habitat definition is needed. (Interestingly, while the koala is a popular subject of study, very little is actually known about its behavior or feeding patterns – especially after dark.)
According to Marsh, the assumption is that whatever tree a koala is seen in, is the tree it likes to eat, which is obviously missing the bigger picture. She and her colleagues set out to discover what makes koalas interested in one type of tree over another.
To do this, the researchers fitted eight koalas in a bush reserve on Victoria's Phillip Island with microphones. The microphones allowed them to track the animals' movements and monitor their feeding and social activities day and night for two weeks.
The team wound up with hundreds of hours of data that helped them evaluate what trees the koalas were in at different times, and when, how often and for how long they fed.
For Dining, Koalas Prefer Trees Heavy in Protein, with Less Toxins
Next, the researchers examined the trees the koalas favored to analyze the nutritional composition of the leaves. This is how they discovered that the trees the koalas chose to rest and sleep in weren't necessarily the trees they preferred to eat from.
Marsh and her colleagues learned that koalas are individuals in terms of how many trees they visit, meals they eat, and how much time they spend eating each day. The koalas seemed to enjoy relaxing in blue gum trees during the day, but chose Manna gums to feed on at night.
The researchers also learned that koalas seem to prefer leaves with more protein and fewer toxins. According to Marsh, "Koalas eat very different amounts from each tree they visit and this is highly dependent on the nutritional value of the leaves." It seems each tree, regardless of species, can have wildly different levels of proteins and toxins compared to the tree right next to it, and this has a big impact on how much the koalas eat.
When They Just Want to Hang Out, Koalas Choose Large, Shady Trees
When it comes to daytime resting and snoozing, the study showed that koalas had a very strong preference for big trees with lots of shade.
Marsh and her colleagues concluded that because koalas spend their lives in trees, they use them for all kinds of purposes beyond feeding, including as shelter and as a way to either socialize with koala friends, or avoid koala foes.
The researchers suggest that since direct observation of koala behavior is difficult, perhaps measuring leaf cuticle fragments or waxes in feces might be a more accurate way to determine the diet intake and behavior of these fascinating animals.