The Orchestra of Love
Spring has sprung in North America (although Colorado was just getting snow), but normally with the increase in daily temperatures and longer daylight hours, animals are starting their mating rituals. My backyard is filled with bird melodies and bickering as the mockingbirds, towhees and scrub jays are in constant battle over mates, nest sites, and food resources to feed their newly hatched babies.
In the land of koalas, things are pretty similar. The sounds that the koalas are making are not as melodic as the songs of birds, but they serve many of the same purposes. At this time of year the male koalas are letting the females (and probably other males too!) know that they are available and are the best choice in town.
Another, more pungent sign that it’s spring is the male koalas’ sternal (chest) glands starting to kick into high gear with the production of a cacophony of over 40 chemicals. It reminds me of hikes out on St. Bees to track koalas, when you can smell a male before you can see him. My work entails examining these sexual traits of koala males.
San Diego Zoo has the largest breeding colony of Queensland koalas outside of Australia: a wonderful accomplishment that has allowed us to examine this iconic species scientifically.
Our large colony (we usually have at least 20 koalas in residence at the San Diego Zoo) has allowed us to examine their breeding behaviors in a microcosm. We can monitor the times that females are getting ready to find a mate as well as who she decides to pair up with and eventually who produces a joey. These exciting events represent valuable data which when analyzed often surprise us when we are finished crunching through the numbers.
What we have found in our colony of koalas is that females seem to be the ones dictating whom they will mate. We use a studbook (developed by a geneticist) to determine which koalas are best suited to one another genetically. In the end though, it is up to each pair to produce the joey: a job many have done successfully since they first arrived in San Diego many years ago.
As a researcher, however, I wanted to go beyond that and so started asking the question: what makes a successful pairing? From those results (as well as data from the field work with koalas wearing GPS collars), we decided to examine what it was about the males that made female koalas choose them over the other their competitors.
Male koalas have two things going for them: wonderful bellows that are both loud and deep, and their odorous chest scent gland secretions. We may not agree, but the female koalas seem to be noticing and preferring these male characteristics.
So don’t let the sleepy koalas trick you into thinking that nothing is going on while they sleep. Males have bellowed (maybe for hours before females show any interest in them) and have also changed how the air around them smells. Both sets of attributes result in giving some males the edge in winning over a mate when the time is right. Females constantly assess both sounds and scents when deciding whom they will be receptive to at breeding time.
The Conrad Prebys Australian Outback is now open at the Zoo, so come see our koalas, and if you’re lucky, you may catch a glimpse (or a whiff) of the mating rituals going on around you.
Jennifer Tobey, Research Coordinator, Division of Behavioral Ecology
San Diego Zoo Institute for Conservation Research