Koala love

I’m often asked questions about koala reproduction and considering that we are now entering the peak of the koala breeding season (at Cape Otway at least), I thought I’d put together a summary of what we know about koala ‘love’. Actually, there is not that much ‘love’ involved and for anyone who had witnessed a male koala that is full of testosterone, harassing a female koala that is not interested in him, you’d know what I’m talking about. The female will scream her disinterest and if the male gets too close, she will fight him off with tooth and claw. Eventually, he will retreat, often bellowing (in frustration?). Ten minutes or so later, he will try again. Observations suggest that he will continue to stay close to his chosen female, sitting in a lower fork of the tree and guarding her closely.

A male trying desperately to get some 'love'. He managed to grab the female but eventually
lost his grip and fell about 5m.

 

He  simply climbed back up the tree to await another opportunity

This male took an interest in me. I'd had the misfortune of being urinated on by a female that we were catching. Considering his obvious 'excitement', I think he may have thought I was a female koala.

 

I have only ever seen a few copulations in the wild. In one, the female went to the male (she actually woke him up). In another, the male went straight to the female, passing another female on the same branch. Obviously, given the number of joeys we see, there are a lot of successful copulations. Around 80% of the females in our Cape Otway population this year have joeys. This means that even the food shortage last year did not disrupt the breeding cycle.

The koala gestation period is around 33 to 35 days. The young is born at the embryonic stage (as with all marsupials) and crawls its way to the pouch. Typically there is only one young although twins can occur. In wild populations, it is likely that only one of these will survive through to independence.

Twins for a female at Cape Otway (photo courtesy of DEPI)

The young latches on to one of two teats and will remain in the pouch for about 6 months. The mother prepares her joey for its eucalyptus leaf diet by producing a faecal pap for the joey to feed on. This helps the joey transition from a milk- to a leaf-diet. At 6 to 7 months of age, the joey (300 – 500g) emerges from the pouch and clings tightly to the mother. It will begin eating leaves although continues to poke its head back into the pouch for milk.

After leaving the mother's pouch, a joey will regularly poke its head back in the pouch for a drink.

 

The mother will carry the joey on its back for around 3 months.

 

By 9 months, the joey will weigh around 1kg, and at 12 months and ~2.5kg it is fully weaned. Weaning usually occurs when the mother becomes pregnant again. The mother will become quite aggressive towards her young. This can be heartbreaking to watch – the mother screaming and lashing out at her young, and the young crying. It is not uncommon to see a few of these rejected young hanging out together. On one of my Earthwatch trips, a recently weaned joey even sought comfort from one of the Earthwatchers. It literally chased her and began climbing her leg.

This joey is nearing independence.

There are still a lot of questions about how koalas select their mates and how long males will guard females. I am hoping that we will get some answers to these questions this breeding season. We have deployed ‘proximity collars’ on males and females in the same area. When koalas wearing these collars are within a few metres of each other, each collar will record the ID of the other collar, the time, and the duration of interactions.