Saturday, March 28, 2020

More About Opposums

North American Opossum with winter coat by Wikimedia user Cody PopeAlthough my Irish-American mother taught me that the prefix O’ (descendent of) was originally part of common Irish surnames such as Kelly, Murphy, Hogan and Kennedy, it would sound odd to my ears were these families to suddenly revert to the Old-World form.

I have the same issue with the distinctly New-World marsupial, the opossum. In the Genesee Valley of New York State where I grew up, these omnipresent critters were known to all as possums, and it still sounds foreign to hear their name pronounced with three syllables.

Of the 103 known species of opossums in the world, nearly all reside in South and Central America (for the record, there are neither possums nor opossums in Ireland). Here in North America, we have just one, the Virginia opossum (Didelphis virginiana).

It seems this animal evolved in South America, first appearing in the fossil record some 20 million years ago. It wandered north about 2.7 million years ago during what is called “The Great American Interchange,” apparently some kind of early foreign-exchange program. This was when northern species like deer, foxes, rabbits, bears, wolves and otters invaded South America. In addition to possums, southern critters which migrated north include anteaters and vampire bats, plus a pile of species that didn’t like our weather, and promptly went extinct here.

Like the skunk, moose, muskrat, woodchuck and so many other animals native to the Americas, these pouched mammals are known to us European immigrants by one of their native names. In this case, opossum is a Powhatan word, first written in English by Captain John Smith in about 1609 at Jamestown in the colony of Virginia. I’ve read that the Powhatan word “apassum” referred to something white and dog-like, but Smith described the beast as being cat-sized, with a tail of a rat, and a head like a pig’s.

Even today, people joke that the opossum was assembled with leftover parts, though I think the platypus takes the prize for that, (webbed) hands-down. I have to admit possums seem quite a menagerie: They have opposable thumbs like apes, koalas and pandas, though their back feet, rather than the front, are the most agile. The only American marsupial, they possess a built-in baby-sling feature just as kangaroos and wallabies do. Their tails are prehensile, able to wrap around and grasp objects the way a monkey can. And with a mouth packed with 50 needle-like teeth, possums are the toothiest North American mammal. Perhaps they’re less of a spare-parts critter, and more like a multi-tool animal.

That analogy may be adept, as possums are highly adaptable, not at all fussy about what they eat or where they live. Their diet can include anything from garbage and rotting flesh, to fresh fruits and veggies, to live amphibians and birds’ eggs. An opossum family of up to thirteen baby joeys is equally at home in a hollow tree in the woods, an abandoned woodchuck burrow on a farm, or under a back porch in suburbia.

Their affinity for carrion and further stinky foods gives opossums a bad reputation, but compared to rats, raccoons and skunks which patronize compost bins and road-kills, they come out smelling like roses. For one thing, possums rarely get rabies. It’s believed their unusually low body temperature makes it hard for the virus to survive, which is why they’re not considered a rabies vector. They are typically docile, and not known to bother people or pets.

In fact, even if a possum was feeling ill-tempered, it would likely be unable to fight back. “Playing possum” is not a strategy, but rather a neurological response akin to a seizure. As its body curls up and stiffens, its lips pull back to expose the teeth, which become covered in foaming saliva. The really fun part is that a foul-smelling fluid oozes from its anal glands. It takes anywhere from a few minutes to several hours for the animal to regain consciousness. It’s no wonder such a compelling performance is encoded in possum DNA. This involuntary reaction is stronger with age, so a youngster might not get the memo to faint for a couple of minutes into a hissing match.

Now that the black-legged or deer tick has become established in our region, Lyme disease and its several variants, as well as other tick-borne illnesses, are real threats. If opossums don’t strike you as cute, you may like them better when you learn they eat about 95% of the ticks which they find on their bodies. They have even been caught on camera chowing bloated ticks off the faces of deer. Given that a fully engorged female tick swells 600 times her original body weight, I guess eating one would be the possum equivalent of having a blood sausage for dinner.

Estimates on the number of ticks they kill vary a lot, but in the course of its two- to four-year lifespan, an opossum could kill as many as 20,000 to 40,000 ticks. While it might sound as if we should all start raising pet possums, let’s put this in context: those numbers represent the offspring of a mere 7 to 14 female deer ticks. Still, it’s better than nothing.

According to researchgate.net, opossums were restricted to the southeastern United States a hundred years ago. At that time their range stretched from eastern Texas up to northern Illinois, then east, skirting just south of the Great Lakes in a rough line across northern Pennsylvania to the coast.

Now they’re found throughout Wisconsin, Michigan, and New England, and in southern Ontario and Quebec as well. When I moved to the St. Lawrence Valley in 2000, locals who had grown up there confirmed that there were not yet any possums in that area. It was not until 2016 that I saw my first road-killed opossum there. Since then, the sight has become more common every year.

It’s unclear whether this is a natural rate of spread, or if it has been accelerated by human-induced weather changes such as longer growing seasons and milder winters. Opossums do not hibernate, so it’s possible that severe cold might be a factor that once limited their range. Regardless, I suggest we welcome the unusual but well-groomed arrivals. We were all immigrants once.

Photo of North American Opossum with winter coat by Wikimedia user Cody Pope.

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Paul Hetzler

Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.

You can read more of his work at PaulHetzlerNature.org or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World




5 Responses

  1. Paul — Altho I enjoyed your ‘possum article, I have to point out one almost deadly thing that ‘possum bring to a farm.

    We’re a horse farm in CT. ‘Possums abound. They enjoy our barn cat’s food. But … you did not mention that when a horse eat grass or hay that a ‘possum had peed on, that horse can died if not treated with antibiotics for a looong time. Don’t know what it’s called. Just know horses suffer and their owners get BIG vet bills.

    My two cents.

  2. Boreas says:

    Paul,

    Thanks for another interesting article. I have always found the gradual global transition from marsupial mammals to placental mammals over the eons fascinating. Hopefully, Australia’s unique “marsupial island” will bounce back quickly from their recent fires.

  3. Tom Vawter says:

    Nice article, Paul. I hadn’t known the Native American origin of the word “opossum”, but I did know that there are various species of “possums” in Australia and the surrounding region. A little research solved the riddle. The famous English botanist Joseph Banks, sailing with James Cook noticed the similarity between the American animal and some Australian marsupials and gave the name “possum” to the Australian animals, which are only distantly related to the American “opossum”.

  4. Tim-Brunswick says:

    Another point which benefits their survival is that they taste “terrible”, apparently even to the other critters in the forest! I’ve observed dead possums carcasses remain relatively untouched in locations from mid October to late February, when they are finally picked apart by crows, fox, fisher, etc., etc.

    Having caught one myself at one point in my younger days in the woods trapping, I parboiled it with onions, celery, and spices in the house and then took it into the woods, built a fire to cook it a bit more and add some smoky flavor, looking forward to a delicacy. Alas my first bite was disappointing to say the least and a couple of samples later I left for the raccoons, etc.

    In later life I’ve learned a lot more about these fascinating creatures, particularly their tick eating habits and when they appear in my yard, I welcome them.

    Not sure whey they’re such a delicacy down South, but they must have a better recipe for sure.

    Thanks for listening!

  5. Allen Lindsay says:

    I entered college (Manhattan) in NY City in Sept. 1951 and began to see opossums, which had recently become established there. The common opinion was that they had come north on produce trains. I hadn’t yet seen one at my home in Cohoes, but had heard of sightings. Ten years earlier, one only read about them.

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