Can the key to saving a species from extinction be in its faecal matter? However outlandish that question may appear, the answer appears to be a tentative yes. This comes from a study on faecal inoculations published in Animal Microbiome by Michaela Blyton and her team from the University of Queensland, Australia. When it comes to food fads, koalas take the cake. Koalas are specialised folivores (herbivores that specialize in eating leaves). They prefer, in particular, the foliage of trees in the genus Eucalyptus. Their choice of food is primarily determined by its protein content, digestibility and toxicity.
The ‘manna-gum’ eucalyptus is one such dietary favourite among koalas. In 2013, over-browsing of the manna-gum leaves at Cape Otway, Australia, led to rampant defoliation and in turn, shortage. This resulted in a large percentage of the koala population getting wiped out due to starvation. What was shocking was that the koalas that preferred the manna-gum chose to starve, rather than try out the leaves of any other kind of eucalyptus like ‘messmate’, which were available in abundance. A smaller group of koalas which were living in a messmate forest, however, preferred those leaves as their staple diet.
The team of researchers led by Blyton attempted to alter the gastrointestinal (GI) microbiomes of the koalas to induce them to try out other eucalyptus leaves such as messmate. They isolated bacteria from the faecal pellets of koalas which consume messmate eucalyptus and administered orally these capsules to 12 captive starving koalas, fixated on supping exclusively on manna-gum leaves. Over the course of 4 weeks, they observed a change in the diet patterns of the koalas in captivity. The koalas which were earlier totally averse to messmate leaves have now taken to feeding on them, on account of the changes occurring in their gut microbiota.
The study suggests that hindgut fermenting herbivores like the koala have GI microbiomes which are relatively unresponsive to dietary changes even over a month. This explains why the koalas did not try to eat a different type of leaf – their GI microbiome was simply not adapted to it! Given the dwindling population of the koalas and high tree mortality rates of the manna-gum, faecal inoculations seem to be the only hope in sight for these tree-loving marsupials.
Puneeta Sreenivas – Science Writer