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Sitting up in their gumtrees, watching the world with little eyes set above the kind of nose you’d expect to find in a craft store. The koala’s fuzzy gray head is adorned with furry white ears, and the end result is a huge bundle of cute that makes you want to squeal.

Picture by Erik Veland


Of course, being an Australian I know our cute koala isn’t as cuddly as it looks. Okay, it is when you actually get to cuddle one at the zoo. Otherwise they’re just plain vicious. Behind those fuzzy paws are some serious claws. They’re surprisingly fast on the ground, and they grunt in the night like a bush pig in a trap. Freaking terrifying to a twelve year old in a tent, let me tell you.

All the same I like koalas. They be fearsome.

Over a mug o’ rum this week, a friend told me an alarming tale about koalas. She said they catch Chlamydia because they are so promiscuous. It gives them a runny bottom, and makes them infertile.

I haven’t found much evidence that koalas sleep around. But they do have weird special sexual organs. Instead of having one head, a koala penis has two. The female has two internal vagina (vaginas?). The sciencey term for the double dippers is “bifurcated” and lots of marsupials are that way endowed. In fact the echidna penis has four heads!

As for Chlamydia, yes, koalas catch it. There are two strains which infect koalas. C. pneumoniae which humans can also catch, and is one of the leading causes of pneumonia in the world, and C. pecorum which some other animals get and causes urinary tract and respiratory infections. Although 40-70% of koalas test positive for Chlamydia, less than a quarter of them have symptoms at any one time. (Just to be complicated, the C in those names stands for Chlamydophila, a separate but very similar genus to Chlamydia. Same thing, different word says I.)

Chlamydia is a bacteria which acts like a virus. It has the usual cell wall, DNA, RNA, protein concoction that bacteria are so fond of, but unlike most bacteria it can’t grow by itself. To reproduce it has to hijack the machinery of another cell (like a human or koala cell). That’s how viruses roll.

It’s bad news for the koalas, as the cure for Chlamydia is a course of antibiotics taken daily – hard to do in the wild.