Koalas may be one of Australia’s most charismatic animals, but there’s still a lot we don’t know about them. For example: what animals prey on them, and how often?

Between 2013 and 2017, 503 free-living koalas got fitted with telemetry collars, which allowed scientists to find them in the wild, record their positions, and importantly, detect when they were dead. Over these four years, scientists tracked koalas and recovered those that perished. Or at least they tried to — some were tracked to the inside of carpet pythons! 

Experienced veterinarians examined the retrievable koala bodies and determined causes of death through a necropsy, which is an autopsy for animals. With these results, the realization that carpet pythons do prey on wild koalas, and knowledge about carpet python behavior, the study authors were able to accurately estimate how many koalas died from carpet python predation. And it was more than initially expected.

Carpet pythons seem to kill more koalas than they can swallow. In most cases attributed to carpet python mortality (62%), koalas were killed by asphyxiation with evidence of attempted ingestion, but the koala carcass was ultimately abandoned.

This finding enabled scientists to pinpoint the signs of carpet python predation attempts: identification of a bite site, slicked fur from the snake's saliva, and damage to the lungs caused by the pythons wrapping their body around the koala’s body. We now know that carpet pythons are the second biggest predator of wild koalas, behind wild dogs (dingo relatives, not to be confused with the dogs we keep as pets). This is an important finding that will allow wildlife managers to identify safe koala habitat.