Ringtail opossums are an Australian wildlife species that is potentially endangered  A number of ringtail opossums that had been orphaned and subsequently raised in captivity were monitored after being returned to the wild  Seventy-five percent of those opossums were killed by foxes, a species not native to Australia
Conservationists concluded that the native ringtail opossum population was endangered not by a scarcity of food, as had been previously thought, but by non-native predator species against which the opossum had not developed natural defenses
There are fewer non-native predator species that prey on the ringtail opossum than there are native species that prey on the ringtail opossum.