Virginia Opossum Skull (Didelphis virginiana)

Virginia Opossum Skull (Didelphis virginiana)

With the exception of the veritable army of squirrels stashing acorns in my backyard, my (live) mammal sightings are relatively rare. I’ve caught glimpses of white-tailed deer and a fisher while walking in the Bourne Town Forest. Occasionally a red fox or a coyote dashes across the road at night in front of my car. I have encountered skunks near my house a few times. But for the most part, indications of these species’ presence take other forms, such as tracks in the mud or snow, or scat left on or near a trail. In other cases, remains of dead animals, such as this skull I recently found in a forested area of Bourne, provide evidence of an animal’s presence.

Skulls of coyotes, foxes, raccoons and opossums are all surprisingly similar, especially when many of the teeth are missing, despite how remarkably different the living animals are. Key features of this particular skull that indicate it’s a Virginia opossum are its size, the number and location of teeth (or in this case, the number and location of tooth sockets), and the prominent sagittal crest. In terms of size, this particular specimen is just over 5 inches long. Based on A Key-Guide to Mammal Skulls and Lower Jaws by Aryan Roest, opossums have “medium” skulls between 3 and 6 inches long. Roest’s guide also describes opossum teeth as including large prominent canines and 5 incisors on either side of the front of the mouth. Although both the canine and incisor teeth have since fallen out of this skull, there is a large cavity indicating where the canine tooth would have been, as well as 5 small sockets on the intact portion of the front of the jaw, confirming that this skull did indeed have 5 incisors on either side. Furthermore, the cheek teeth that do remain are a mix of “tearing” and “grinding” teeth, typical of an omnivore like an opossum. Finally, the pronounced sagittal crest, a lengthwise ridge on top of the skull, is also a helpful identifying feature. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles.

The Virginia opossum (Didelphis virginiana) is the only extant marsupial (pouched mammal) native to North America. Although widespread throughout the eastern United States, they are fairly recent additions to Cape Cod. The first reported Virginia opossum on the Outer Cape was in 1976 at Brewster’s Nickerson State Park. They are characterized by a long snout, a long, prehensile, scaly tail, short, black ears, and long gray guard hair. My favorite description of this unique animal, however, comes from A Guide to Nature on Cape Cod and the Islands, in which Virginia opossums are described as “a strange composite sort of creature” with the “general shape of a pig; the nose of a fox; the fur of a raccoon; thin, papery bat-like ears; the pouch of a kangaroo; a rat’s tail textured like snakeskin (from which is can hang like a monkey from tree branches); the size of a cat; the walking gait of a skunk; and rear feet with nailless thumbs that look uncomfortably human”.

Part of the reason we so rarely encounter them is that Virginia opossums are mostly nocturnal. They mainly feed on insects and carrion, but also consume mushrooms, fruits and seeds (which makes sense given the omnivorous set of teeth they possess). Finally, although the Virginia opossum’s defense behavior includes hisses, growls, screeches, and bearing its teeth, it is best well known for “playing possum”. When facing a particularly strong threat, Virginia opossums will resort to feigning death, during which the animal actually falls into a catatonic state.

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