Grubby’s story is unusual, but the species she belonged to already stands out. The Virginia opossum is the only marsupial naturally found in the United States and Canada, and it comes with a surprising set of biological quirks.

North America’s only native marsupial

Unlike most local mammals, opossums give birth to tiny, underdeveloped young that crawl into a pouch on the mother’s belly. There they latch onto a nipple and continue developing until they are strong enough to ride on her back. This reproductive strategy is typical of marsupials, but in North America, opossums are the only animals that do it.

Playing dead is not an act

Opossums are famous for “playing possum,” but the behavior is more automatic than dramatic. Under extreme stress, their bodies can go into a catatonic state. They collapse, their tongues may hang out, and they release a foul-smelling fluid. To a predator, the animal smells and looks like something that has been dead for a while, which often ends the chase.

Tick vacuum and neighborhood clean-up crew

These animals are opportunistic eaters. They will scavenge roadkill, raid pet food bowls, and happily hoover up beetles and slugs. Studies and wildlife groups point out that a single opossum can eat thousands of ticks in a season, which makes them unlikely allies in the fight against tick-borne diseases.

Unusual resistance to disease and venom

Opossums have a lower body temperature than most mammals, which appears to make them poor hosts for the rabies virus. Recorded rabies cases in opossums are rare compared to many other wild species.

They are also remarkably resistant to the venom of many pit vipers. Researchers have identified a peptide in opossum blood that can neutralize certain snake toxins in lab tests, raising the possibility of new treatments for snakebites.

Living fossils in the suburbs

Fossil relatives of modern opossums stretch back tens of millions of years. Despite that long history, the animals alive today look surprisingly similar to some of their ancient cousins. That evolutionary “conservatism” suggests that the opossum’s generalist lifestyle has worked for a very long time.