Five Gross Facts About Koalas

  • Posted 11.26.15
  • NOVA

Think koalas are cute? Think again. Find out just how strange these animals are in this episode of Gross Science.

Running Time: 03:21


Five Gross Facts About Koalas

Posted: November 26, 2015

Think koalas are cute? Think again. Here are five gross facts about koalas.

I’m Anna Rothschild, and this is Gross Science.

Number 1. Baby koalas, called joeys, eat their mothers’ poop. For the first six months or so after they’re born, they drink milk from a teat in their mom’s pouch. But then, for several weeks, they eat…fecal matter. The joey sticks its head out its mom’s pouch and nuzzles her butt. She releases some normal poop pellets, followed by a runnier, protein-rich substance, called pap. The pap helps the baby grow, and is full of the mom’s gut bacteria, which could help prepare the joey for its adult diet of eucalyptus leaves.

Number 2. Like many other marsupials, the penises of male koalas have two prongs. But, that’s nothing compared to the female, which has two vaginas and what’s called a vaginal cul-de-sac. Sperm travels up the vaginas on either side, and babies leave through the cul-de-sac, actually breaking through the bottom. After birth, the cul-de-sac heals.

Number 3. Males use a loud belching noise called a bellow for attracting mates and for other communication. A unique vocal organ at the back of their throats makes their calls extremely low. In fact, the koala’s bellow is about 20 times lower than it should be for an animal of its size.

Number 4. A mature male koala has a scent gland on his chest, which oozes dark, smelly gunk that he rubs on trees. No one’s entirely sure what the gunk’s for, but it could be to signal that he’s ready to mate, or to mark his territory. Koalas aren’t known to be super territorial, but that’s not always the case…

Number 5. Wild koalas in Australia face some major threats, like habitat destruction, brushfires, an HIV-like virus that suppresses their immune system, and even chlamydia. The strains that infect koalas are different from the sexually transmitted disease we get. But koala chlamydia also spreads through mating, and mothers can transmit it to their joeys. It can make the animals blind, incontinent, infertile, and even kill them. And it’s pretty prevalent—in some places up to 90% of the koala population has been infected.

Now, it’s not clear exactly how critical koalas are to maintaining stability in the ecosystem. But personally, I don’t want to risk it. We simply don’t know what losing these guys to disease or habitat disruption could mean for eucalyptus forests. And besides, koalas are deeply important cultural icons—think about it, they’re basically synonymous with “Australia”…along with kangaroos and vegemite. So, no matter how strange these animals are, I for one wanna save them.

I guess you’re still kinda cute. Ew.



Host, Producer, Editor, Animator, Additional Research
Anna Rothschild
Researcher, Writer
Elizabeth Preston
DP, Sound, Additional Research
Ceri Riley
Perfectly B
Music Provided by APM


Original Footage
©WGBH Educational Foundation 2015
Audio and video of Koala Velar Vocal Fold Vibrations
Courtesy Dr. Benjamin Charlton
A video recording of a bellowing male koala (Phascolarctos cinereus) (called Andy) at Lone Pine Koala Sanctuary.
Movie S1 from: Charlton, B. D., Ellis, W. A. H., McKinnon, A. J., Brumm, J., Nilsson, K., & Fitch, W. T. (2011). Perception of Male Caller Identity in Koalas (Phascolarctos cinereus): Acoustic Analysis and Playback Experiments. PLoS ONE, 6(5), e20329.
Koala (Phascolarctos cinereus) newborn in pouch, Australia
Getty Images/Roland Seitre
young joey in pouch eating pap
Portrait of male Koala bear, Phascolarctos cinereus, 3 years old, in front of white background, studio shot
Koala chases girl riding an ATV and attacks
Ebony Churchill/
Cutest Koala
Wikimedia Commons/Erik Veland
Phascolarctos cinereus -ZooParc de Beauval, France -upper body- 8a
Wikimedia Commons/frank wouters
Baby Koala
Wikimedia Commons/حسان هواري
Koala with young
Wikimedia Commons/Brian Dell Bdell555
Koala Eating
Wikimedia Commons/(--Pumpmeup)
Friendly Male Koala
Wikimedia Commons/Quartl
Wikimedia Commons/Summi
A cranky-looking koala, sitting beside the road on the way to Apollo Bay
Flickr/Shiny Things
(used with permission from author)
Wikimedia Commons/Mike R
The World Factbook - Australia - Flickr - The Central Intelligence Agency (19)
Wikimedia Commons/The Central Intelligence Agency
Koala being treated for chlamydia
Ari Daniel/WGBH Educational Foundation
Koala and joey
Wikimedia Commons/Benjamint444
Koala Eating (3337014192)
Wikimedia Commons/Rennett Stowe from USA
Australia satellite plane
Wikimedia Commons/Reto Stöckl / NASA Goddard Space Flight Center
Macropus rufus in ZOO Plock
Wikimedia Commons/Bardrock
Vegemiteontoast large
Wikimedia Commons/Tristanb


(used with permission from author)
Squeak Pack/squeak_10
Produced by WGBH for PBS Digital Studios


Cutest Koala
Wikimedia Commons/Erik Veland


Want more info?

Additional info about the koala life cycle:

Info on the koala reproductive system:

Primary literature on the koala’s unique vocal organ (article behind paywall):

Nature article on the koala’s bellow:

NOVA/PRI’s The World report on koala chlamydia:

Related Links