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Column: Marsupial alert

A small animal, gray with a skinny, bald tail, made its way over the snow, disappearing now and again on the backside of a drift. I stopped the car, snapped a photo that didn’t capture much, and waded into deep snow in pursuit of a truly odd animal: An opossum, and only the second one I’ve seen alive.

They’re seen more often as roadkill. Omnivores, they eat just about anything including roadkill, and risk being run over to become that in turn.

The opossum disappeared down a tunnel in the snow that had signs the animal had exited and entered it at least a few times.

Nocturnal animals often venture out in the daytime as winter advances and fat reserves or food stockpiles dwindle. It’s also mating time for opossums. More about that later.

Years back I caught an opossum in a have-a-heart trap intended for a garden-raiding woodchuck. It was dead and I felt badly for not checking the trap more often or for the fright that must have done it in.

I asked Carl to remove it, and he came back from the mission smiling. Opossum was playing possum and Carl had noticed subtle signs of life. We opened the trap up but the opossum continued to be inert.

I read now that “playing possum” is an involuntary reaction to perceived threat — not an actual strategic choice the animal makes. Typically an opossum will hiss and growl, and if that fails to deter a predator it goes into temporary paralysis similar to a faint. “Fight or flight” does not apply to opossums.

We didn’t notice drooling or other leakage said to be foul smelling, all the better to repel a predator. In a faint, their teeth are bared. Opossums have a lot of teeth.

To lure the inert opossum out, I spread peanut butter on an overripe peach and placed it outside the trap. Hours later both were gone.

I learn now that opossums have a keen sense of smell, perhaps keen enough to wake it from its faint.

As for breeding, opossums are a mammal but they belong in the marsupial — not placental — branch of the mammalian family tree. Nourishment is not delivered by placenta.

Instead, tiny young the size of raisins are born after a brief gestation period of about 12 days. They crawl up and into the mother’s pouch, latch on to one of 13 nipples and don’t let go for two months.

A typical brood falls a bit short of 13.

The newborns are called “living embryos” as a lot of development that takes place in utero for placental mammals takes place ex utero in the mother’s pouch.

When the young do let go, they’ll hop on board the mother’s back. Opossums move around a lot, from den to den. Females are not large, the size of a small cat, so carrying young must have its challenges.

As for other physical oddities, their hind feet have what serves as a thumb, a clawless fifth digit that assists dexterity. The tail is prehensile, serving as a fifth hand. It curls around and carries nesting material that is gathered and passed back. The young can hang by their tails but eventually reach a weight too great for hanging.

With hairless ears and tail, opossums have to line their dens with lots of insulating leaves and grasses to keep cold at bay. In the depths of winter, they’ll retreat to a den and live off fat reserves put on in the fall.

Frostbite happens.

Most species accounts I found state that “our” opossum, the Virginia opossum, is the only marsupial in North America, but Meade Cadot at the Harris Center says there’s another North American opossum. The southern or common opossum is found mostly in South America with a range that stretches northward in Mexico.

I was hoping I could say that our backyard opossum is the only marsupial in the Northern Hemisphere. . . Almost the only.

And it is a backyard species despite seldom being seen. Like skunks and raccoons, opossums do well near humans where compost piles, birdfeeders, fruit trees and other edibles are available.

Opossums are short-lived, two years on average. For reasons I can’t determine, senescence occurs early for the species. It seems an odd evolutionary trait. Farther south an adult female will produce two and every three litters in a year to make up for a short breeding career.

As newcomers this far north, one litter is the rule.

And newcomers they are. Furbearer biologist Eric Orff’s account on the New Hampshire Fish and Game web site says they showed up in New Hampshire in the 1960s, moving north along river corridors at first. In 30 years they reached the Lakes Region, and now they’ve been reported way north in Coos County.

His account ends:

“Opossums were once thought to not be able to survive such a cold climate, but they just keep plodding north on frostbitten feet.”

Backyard Birder by Francie Von Mertens appears every other week in the Monadnock Ledger-Transcript.

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