Watch Usually Solitary Wild Koalas Captured On Film Snuggling Socially For First Time

In popular imagination, koalas’ reputation has gone up and down. Although their button eyes and ridiculously furry ears made them an early favorite in children’s literature, one Australian minister for tourism denounced them as “Flea-ridden, piddling, stinking, scratching, rotten little things.” Documentaries showing them mating convinced many Australians he was right, although when an environment group conducted a search for Australia’s most beloved species by dressing up fundraisers in different costumes, those in koala onesies raised the most.

However much people may love or hate koalas, zoologists have been confident they don’t like each other much, mothers and joeys aside. To the extent they interact rather than ignore each other, fights over territory are the norm, aside from some bonding among females in captivity, and one isolated report.

Consequently, Deakin University PhD student Darcy Watchorn, now at Zoos Victoria, was very surprised when he saw three subadult males sitting companionably on a branch, with two engaging in grooming and sniffing each other’s genitals. Subsequently, the third koala joined in while one and then the other of the original pair took a break. Nor was this just a brief encounter, Watchorn witnessed the interactions continue for two hours, although one of the trio left after about an hour. Two of the three were seen behaving similarly the following day.

Koalas are endangered over most of their range, thanks to habitat loss, dog attacks, and chlamydia. However, Watchorn was working in the Otway Ranges, where a few years before koala populations had boomed so much that they killed most of their food trees by overharvesting. Since then, the population has been maintained through contraceptives, but the isolation of the area and boom-bust cycle has led to very low genetic diversity.

Overcrowding often leads to aggression rather than affection, but Watchorn told IFLScience, “It depends on the context and the species. I saw quite a lot of fairly violent behaviors among older males, and these were more frequent than among lower-density populations.”

Watchorn wrote up the observation precisely because it was so unusual. The only previous account came from French Island, on the other side of Melbourne, another area with a dense koala population with low genetic diversity. Watchorn thinks it is possible that similar genetics contributed to the unusual friendliness of the koalas he watched, something known as the “kin recognition hypothesis.”

The fact all three individuals were not fully mature (3.5-5.5 years old based on how worn their teeth are), as were those on French Island, was probably also a factor. Female koalas have been observed grooming and interacting sexually, (described as stress release) but only in captivity.

Watchorn’s work isn’t all good news for koalas’ reputations. He also witnessed a joey fall out of a tree as a male brushed it aside when it attempted to mate with its mother, something Watchorn wrote up in a previous observation.

The joey survived the fall, thanks to landing in soft grass and a general robustness of the species, but Watchorn says he thought it was too young to return to safety on its own, having only recently left the pouch. Watchorn chose to violate biologists’ usual non-intervention, and returned the joey to its mother, rather than risking it being killed by a fox. It appeared healthy over subsequent months. Without that action, Walchorn told IFLScience, this could have been the first recorded case of “accidental infanticide” resulting from male koala’s aggressive approach to mating.

Walchorn’s observations of the friendly subadults is published open access in Australian Mammalogy, while the report of the falling joey is published in the same journal.