Friends on Facebook were recently discussing opossums, and one of them referred to them as ‘rodents’. Despite inner struggle, I failed to resist my impulse to correct her. I did, however, prevent myself from regaling her about opossum natural history so I will instead regale you, my nonexistent audience, as a safety valve.
When I was a kid, there were no ‘possums in Minnesota but, thanks to global warming, they started to show up in large numbers in my late twenties. I’ve always regarded a possum sighting as a major event, partly due to their rarity up here and partly because of a half-remembered David Attenborough anecdote from my childhood.
The story, as I remember it, turns out to be pretty accurate. South American used to be an Australia-like evolutionary backwater, with all kinds of stupid and ridiculous animals prospering undeservedly. When North America finally smashed into South America, it let loose a torrent of murderous, high-tech placental mammals which swiftly devoured and/or out-competed the South American natives. There was a massive extinction event, after which South American fauna looked more like the rest of the non-Australian word with big, fancy, high-speed placental mammals roaming around, and relatively few comically large flightless birds, plains-dwelling crocodiles, etc.
Opossums, being old-fashioned marsupials, are a notable survivor of that cataclysm. They’re ancient South American refugees, still traveling north to this day.
Catching up on the history, though, I’ve now learned that opossums aren’t the only escapees — two other notables are porcupines and armadillos. These three, obviously, also make up the Holy Trinity of Roadkill. That can’t be a coincidence! The fastest of the South Americans were no match for their more efficient North American attackers, but those South Americans who relied on ridiculous, passively horrifying defense techniques fared pretty well.
All three (but especially possums) survived by acting like roadkill — pretending to be dead, stinky, and unappetizing enough that the newly invading predators were baffled and disgusted and simply left them alone. In a sense, they invented the concept of roadkill long before there were actual roads. This strategy carried them not only through the North American invasion, but also led them safely through the next great extinction event (the one where humans showed up and ate absolutely everything in the Americas that was even remotely delicious.)
Only now, finally, in the 20th century, has an enemy appeared that is undaunted by spines, armor, and grossness. The one technique that served so well through so many disasters (that of simply lying down and waiting for the threat to pass) is poignantly ineffective in the face of a speeding car. It is, I suppose, a lot easier to defend yourself against malice than against indifference.