According to the Massachusetts Division of Fisheries and Wildlife, there are no opossums on Martha’s Vineyard or Nantucket.

Tell that to the furry marsupial captured last week. If it looks like an opossum, plays dead like an opossum, hisses and bares its teeth like an opossum, it must be an opossum. And it was an opossum, but not a possum. Technically a “possum” is the opossum species found in New Zealand and Australia, but not North America, though colloquially this abridged name is often used.

Our continent only has one native opossum species, the Virginia opossum, which also holds the title of being the only native marsupial in the United States. This species and the common opossum, which is native to South America, are sometimes kept as pets, and both varieties are occasionally released inadvertently or intentionally into the wild. 

The latter, intentional release, is a problematic situation, often instigated by well-meaning folks due to the reputation of these mammals as tick-eaters. While they do eat ticks, the damage that non-native and non-endemic opossums could do once they are introduced and breeding in the places where they aren’t usually found, like the Islands, far exceeds their use for pest management.

Historically, there have been only a few sightings of opossums on the Island. Alan Keith, Island birder, natural historian, and author of The Mammals of Martha’s Vineyard in the Dukes County Intelligencer (1969) and Island Life: A Catalogue Of The Biodiversity On And Around Martha’s Vineyard (with Steve Spongberg, 2010), documents two sightings of common opossum on Island in the last 75 years. An adult male was found dead in 1965, hit by a car, and another adult was discovered alive in 1966 (as reported by this paper).

Regardless of how this recently found opossum got here, I wouldn’t attempt to correct the teeth-baring mammal on its proper locale. Though known to “play possum” and act dead, when they do decide to defend themselves, opossums take a tooth-showing stance to scare off predators. And it generally works. Those teeth and a few other characteristics give the opossum bragging rights for an anatomical superlative: those choppers, numbering 50, make the opossum the toothiest land mammal on this continent.

This is not this animal’s only curious feature. Being marsupials, opossums carry their young in a pouch. Didelphus, its genus, means double womb, with the pouch acting as that second place for the developing young.

The pouch, and young’s growth within, has been the cause of some mistaken beliefs about how these animals mate and develop. After observing female opossums caring for their young in the pouch, American colonists surmised that reproduction occurred in her nose and that the young were born from the female’s nose through a sneezing action. It must have been some haphazard observation, indeed.

A final fun fact concerns opossums’ brains. They have the smallest brain-to-weight ratio of any North American mammal and must not have been the smartest animal in the ark.

So, with their limited brain power, you can’t blame them for being in the wrong place at the wrong time. Opossums are appropriate pets and make sense in places where they are native and can survive and thrive in their environment. Here, they can change habitats, bring diseases like rabies, and alter indigenous wildlife populations. Ultimately, the captured opossum was turned over the wildlife authorities and hopefully the Island is again, opossum-free.

Resist the urge to purchase, relocate and release these animals for any reason. When it comes to discharging harmful invasive species into the environment, be afraid of unintended consequences for the released animal and the environment.  In the words of Pogo Possum (cartoonist Walt Kelly’s marsupial messenger), “We have met the enemy and he is us.”

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.