Australia's iconic marsupials are under threat, and their salvation could lie in changing the microbiome of their guts, broadening their diets.

Koalas have the remarkable capacity to live off the leaves of eucalyptus trees, which other species find poisonous. The price of avoiding competition is expending so much energy breaking down the toxins they end up sleeping 18-22 hours a day.

Moreover, to a koala, not just any eucalyptus leaves will do. They're notoriously picky, insisting on only eating leaves from particular eucalypt species, often frustrating zoo-keepers by refusing to eat what they are given. It's just as well they're so cute, or no one would bother feeding them.

Being so adorable, however, means many people are out to save koalas from themselves, including Dr Ben Moore of Western Sydney University. Moore told IFLScience koalas across most of the continent are dying from habitat loss, dog attacks, and chlamydia, but in certain pockets their problem is the reverse. In these areas koalas are so numerous they eat their favored trees until the food supply crashes, taking the koala population with it.

However, Moore noted a few koalas have a solution – dietary diversity. Most koalas in the Otway Ranges favor manna gum, unsurprisingly as it has more protein and fewer toxins than the alternative, messmate. However, a few koalas have learned to eat messmate, allowing them to flourish when the manna gum supply crashes.

Moore found the difference lies in the gut bacteria; the fortunate koalas have microbes capable of processing messmate's higher toxin load. He then experimented with collecting fecal samples from koalas in messmate trees, mixing droppings with water and centrifuging the product to get a concentrated bacterial layer, which was made into pills fed to ordinary koalas 2-3 times daily.

The results have yet to be published, but Moore told the American Society for Microbiology's annual conference that the experiment was partially successful. Many recipient koalas' gut contents changed to the point where they could digest messmate. Unfortunately, most of them still refused to do so. As Moore pointed out to IFLScience, these koalas have been eating manna gum all their lives, and possibly learned to do so from their mothers. Shifting is not easy, although it is possible they would try if faced with starvation.

Moore regards the work as a long way off practical application, but thinks the first step will be giving bacteria transplants to rescued koalas, whose microbiomes have often been destroyed by antibiotics anyway. This could lower the cost of keeping koalas in captivity, and might eventually be extended to give options to wild koalas during times of scarcity.

Moore told IFLScience the work could be extended to other species with highly specialized diets, such as packrats.

[H/T: The Guardian]