We have finished analyzing most of the data on the chemical communication of male koalas (see Jennifer’s blog, Smelly Koalas). One of our main goals was to determine the chemical make-up of the scent gland secretion, which we have now completed. An organic chemist, Todd Nute, helped us identify all the chemicals. He took the swabbings we collected and then ran them through a special analytical chemistry machine that uses a heating process to break apart the scent exudate and identify individual chemicals using a computerized catalog of chemicals.

It turns out that there are a variety of chemicals found in the koala scent secretion. We have been able to identify 37 chemicals, and this number may actually be closer to 50 because not all of them were found in the standard catalogs. This is a large number of chemicals; in comparison, marsupials like feathertail gliders have been found to have only three chemicals in their scent secretions.

The chemicals we have identified are not unique to koalas. One of the chemicals we found is hexanoic acid, which is commonly referred to as ” goat smell” (want to guess why?). There is also acetic acid, or vinegar, that was found in the scent exudate. The acids are what make the koalas smelly. There are other chemicals that are found in the scent exudate that are not necessarily smelly but help with keeping the scent around. We found two chemicals that do not have strong odors, but they are oily substances. These two chemicals do not dissipate until they are exposed to very high temperatures. This means that they appear to be chemicals that allow the smell of a koala to linger for a long time on most substrates, so a koala could mark a tree and his scent may linger for days or weeks. In this way, koalas that sniff a scent-marked tree might know who is in the tree.

So now we have proof: koalas are smellier in the spring. We also now know that there are quite a few chemicals that produce that smell and others that allow them to linger for the enjoyment of all around!

Jennifer Tobey is a Research Fellow in the Behavioral Biology Division of CRES.

Here’s more information about Jennifer’s study.

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