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A Female Opossum’s Pouch

The Virginia Opossum (Didelphis virginiana) is found further north than any other marsupial in the world, and is North America’s only marsupial. Like the kangaroo and koala, the female Opossum possesses a pouch which acts as a nursery for her young.  After a very brief gestation period of 11-13 days, up to 20 embryonic (each the size of a honeybee) young climb (witnesses say it’s more like “swim”) from the birth canal into the pouch, where 13 teats are waiting for the first 13 babies that attach themselves. The mother helps by licking the hair leading into the pouch, providing a moist path for the young to follow on this first long and arduous journey they undertake. 

Once a young Opossum latches onto a teat, the teat swells in the Opossum’s mouth, helping it to remain attached for a little over two months during which time it receives nourishment and continues its development.  At the point when they are too large to be contained in the pouch, the young leave and are often seen hitching a ride on their mother’s back. (Photo: the interior of a female Opossum’s pouch, showing some of the 13 cream-colored teats)

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Elimination, Deduction and Perseverance Help You Read a Track Story in the Snow

My hope is that I can share my natural discoveries with my readers in such a way that they can feel they are experiencing them along with me.  One photograph often doesn’t do the experience justice, especially when it involves the unveiling of a track story.  The following photographs illustrate a recent discovery of tracks in the woods, and what they revealed.

Although the snow conditions didn’t lend themselves to showing the details of these tracks, I knew they weren’t tracks that one commonly comes upon. Bobcat, fox, fisher, otter, coyote, porcupine, deer – the likely suspects were quickly ruled out due to size and track pattern. After following the tracks for a while, a line running down the middle of the tracks appeared. This quickly narrowed down the field of likely suspects: what animal that is active in winter has a tail that would drag?  A bit more sleuthing revealed the well-worn paths this animal had created to and from its den, along with some clear individual tracks. Due to the opposable thumb on the hind feet, Virginia Opossum tracks are very distinctive and opossum tails often leave drag marks in the snow. Following the trails from the den confirmed the identity of the track maker, as unfortunately one trail led to the body of the opossum.

These tracks were fresh – and the discovery of them took place just a day or two after our recent temperature plunge.  Although (the formerly strictly southern) opossums have extended their range into northern New England and southern Canada, they still are very susceptible to the cold, suffering frostbite on their ears and tails regularly. My guess is that our only marsupial couldn’t withstand the recent cold temperatures and succumbed to them.  Already, its body was feeding other more cold-hardy forest dwellers.

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Virginia Opossum Tail of Woe

Congratulations to Rebecca Weil, the first (of many) NC readers to recognize Virginia Opossum tracks, tail drag and all!

Opossums are a southern marsupial that have extended their range into northern New England in increasing numbers since about 1900.  They are able to survive here, without hibernating, in part due to the fact that they store fat under their skin and in their tail which helps sustain them through long, cold winters. 

Opossums that live in the Northeast are vulnerable, however, to the cold and run the risk of having their relatively hairless ears and tails frostbitten. In fact, it is unusual to spot an opossum that has spent a winter here and not lost at least part of one of these appendages from frostbite (see pictured Virginia Opossum tail after losing its tip).

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Virginia Opossums Breeding

2-18-19 opossum 025If you see a Virginia Opossum in your travels, it could well be on the hunt for a mate at this time of year. It’s even possible you may hear one if you are close enough and the timing is right, as male opossums attract females by making clicking sounds with their mouth.

The breeding practices of this marsupial are unusual, to say the least. The male opossum has a bifurcated (two-pronged) penis (see photo inset), and the female has two vaginas. Not only is their reproductive anatomy somewhat unusual, but the behavior of their sperm is as well. During maturation, sperm pair up inside the male reproductive tract and remain paired after entering the female. Just prior to fertilization the sperm pair separate (into two spermatozoa). This phenomenon occurs only in American marsupials, and not Australian. No definitive explanation exists for this, but perhaps paired sperm increase motility in the female reproductive tract.

(NB: Having an opossum on your land is a real asset – according to biologist Richard Ostfeld, one opossum can kill and eat some 5,000 ticks in a single season. Opossums are said to destroy roughly 90 percent of all the ticks they encounter.)

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An Opossum’s Opposable Thumbs

11-22-16-opossum-hind-foot3-untitled-1Virginia opossums have expanded their range into northern New England, but are still not commonly seen, except, perhaps, lying on roads where they met their demise. There is much to admire about opossums: they are the only North American marsupial, they have more teeth than any other North American land mammal (50) and they possess a prehensile tail and opposable thumbs (both of which are rarities among non-primates).

The recent discovery of a road-killed opossum provided me with an opportunity to examine its feet at close range. An opossum’s front feet have five toes, each bearing a nail. Their hind feet also have five toes, but only four of them have nails. The fifth toe, or “thumb,” lacks a nail and is opposable, allowing opossums to grasp branches and to climb. If you see their tracks, the hind foot is easily discernable from the front due to the fact that the thumb is at a 90-degree angle to the other toes.

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Opossums Scrounging

3-19-14 opossum2  021Within the last century the Virginia Opossum has extended its range northeastward and now occurs sporadically throughout most of New England. Its adaptability to a great variety of habitats and its omnivorous diet (is there anything an opossum won’t eat?) have enabled this marsupial to live in much colder climates than it initially inhabited. As long as food can be found,the opossum’s greatest challenge is dealing with New England’s cold winters. Lacking much hair, the ears and tail of an opossum often suffer from frostbite, turning black at the edges (ears) and tip (tail). Look for signs of this nocturnal scavenger under bird feeders – in the winter it can even be seen foraging in the daylight, as the opossum in this photograph was earlier this week. (Thanks to Dotty Cummings for photo op.)

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