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The Recorder - The Virginia opossum

Published: 12/2/2019 7:00:16 AM

Two weeks ago, I wrote a column about feeding birds. I discussed the different types of seeds that are commercially available and attempted to offer tips on which seed should be presented in what kind of feeder for different species of birds. In general, you can read about feeding birds all you like, but at some point, you must put out an offering, see who comes for it and make adjustments. Basically, once you start feeding birds, you start practicing the art of science.

However, as many of you noted, birds are not the only animals that are attracted to bird feeders. In fact, a wide variety of our native mammals will also avail themselves of an easy meal if presented with the opportunity. The species most likely to cause humans apoplectic fits is the gray squirrel. On the other hand, the species most likely to cause substantial damage and raise a genuine alarm is the black bear. Both of these mammals are native to North America. Both were here before any humans knew what North America was (including Native Americans) and both are just doing their respective things. Bears are just big.

It is important to remember that there are many other mammal species that might also visit feeders. The only “problem” is the fact that many of them are nocturnal, which makes it difficult for people to watch them. Further complicating matters is the fact that winter is a season when many of these mammal species hibernate (think skunks), or at the very least they will hunker down for a long winter’s nap.

It is during this time of year, when the weather is cold and food is becoming more and more difficult, that you might catch sight of one mammal that tends to be nocturnal but occasionally comes out during the day if there is a meal to be had. The mammal I am speaking of is the Virginia opossum (Didelphis virginiana).

The only marsupial native to the United States, the Virginia opossum is generally just called an opossum this far north. I will do the same to save space. About the size of a house cat, the opossum is an animal that can’t really be described as cute. Its long, naked tail, which has a definite pink color to it, is prehensile, meaning it can wrap around branches and hold on tight. The body of the opossum is covered in coarse gray hair and its face is white with black eyes and hairless black ears.  

Because they are marsupials, opossums do not give birth to fully developed young. Instead, they give birth to tiny pink offspring that are still in the embryo stage. These tiny creatures must then find their way to the mother’s pouch and clamp onto one of the many nipples that will provide nutrients for further growth. Placental mammals (like humans, dogs and deer) accomplish this delivery of nutrients with an umbilical cord in utero, where it is generally safer for a baby mammal to grow.

A female opossum can give birth to as many as 25 offspring in one litter, but this is something of an insurance policy because many of the babies die before they reach the pouch. Then there is the problems that the mother only has 13 nipples (marsupials are apparently so odd that they even have an odd number of nipples) in the pouch. As a result, it is not uncommon for only six to nine of the babies to live long enough to see the light of day.

When the pouch becomes too crowded, the babies will venture out into the world, often clambering up onto their mother’s back to catch a free ride. I have never seen a female opossum laden with babies like this, but it is definitely on my naturalist’s wish list. This arrangement can’t continue for long because the growing babies become too large to remain passengers. The kids get the “heave-ho” and then the mother will have one or two more litters. It is possible that one female opossum can produce up to 30 viable offspring per year. Yikes.

Sadly, opossums are regular victims of car collisions. As with many of our nocturnal mammals, we tend to see them dead in the road rather than alive in our yards, but every once in a while we get lucky. I took this photo of an opossum in my mother’s back yard several years ago.  As one of those young opossums trying to figure out life on its own, it was under one of my mother's feeders looking for seed on the frozen ground.

As the weather continues to creep closer and closer to full-on winter, keep your eyes peeled for signs that mammals are visiting your birdfeeders. Especially if there is a slight dusting of snow, you may be able to see the tracks of visitors that came in the night. Often, this is the only evidence that the animal community in your yard is much larger than you might otherwise think.

Bill Danielson has been a professional writer and nature photographer for 22 years.  He has worked for the National Park Service, the US Forest Service and the Massachusetts State Parks and currently teaches high school biology and physics.  Visit www.speakingofnature.com for more information, or go to Speaking of Nature on Facebook.

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