D:        I haven’t seen any “don’t feed the koalas” signs around this koala reserve Yaël. Do you think I can offer that one a carrot? It’s probably bored from eating nothing but eucalyptus leaves all day.

Y:        It may be bored, Don, but I don’t think it has a choice. Sometimes koalas won’t even eat species of eucalypt that aren’t their preferred choice.

D:        They’re that picky?

Y:        It’s more than that—their stomachs can’t handle it. In 2013, researchers witnessed how that can devastate koala populations after seeing what happened on Cape Otway in Victoria, Australia. The koala population there ate all of their preferred eucalypt tree species, the manna gum, until there were no leaves left. Rather than eating leaves from another eucalypt tree, the messmate, seventy percent of the koalas starved to death. There are some koalas who only eat messmate, so scientists wondered whether these koalas just didn’t have the proper microbiome to eat the species, and if there was something they could do about it. To find out, they caught wild koalas that only ate manna gum. Then they collected feces from other koalas in the wild that ate messmate and made it into capsules. They gave the capsules to the manna gum-eating koalas they’d captured. After monitoring how much messmate these koalas were willing to eat afterward and analyzing their microbiomes, the scientists concluded that the fecal transplants had indeed changed the koalas’ microbiomes to allow them to eat more messmate. In the future, scientists could give capsules to koalas to adjust their microbiomes before moving them to areas with different plant species.

D:        Well, more carrots for me, then.