Chlamydia, a type of sexually transmitted disease also found in humans, has hit wild koalas hard, with some wild populations seeing a 100 percent infection rate.

The infectious bacteria usually aren't fatal, but they can severely impact a koala's health. That's a concern, as the International Union for Conservation of Nature considers the fuzzy mammal vulnerable to extinction, mostly due to habitat loss.

Young koalas in the pouch also get it from eating their mom's pap, a "very nutrient-dense fecal matter" that joeys eat after breastfeeding but before they start on eucalyptus leaves, she says. The pap may allow the koala's gut microbes to digest otherwise toxic tannins in eucalyptus, the species' main food source.

That's why Dahlhausen led a recent