November 9, 2017
By Paula Goodwin
Opossums:Beneficial Wildlife Neighbors
The Virginia Opossum (didelphis virginiana) is found in Acton and throughout Massachusetts except for Dukes and Nantucket counties. The Opossums’ preferred habitat is on the edge of forests near streams and wetlands. It is one of the few animals that is becoming more common, although its natural life span is just about 2 years. The Opossum is North America’s only marsupial, (from Latin meaning “pouch.”)
Male opossums are called jacks and females are called jills. After a pregnancy of just two weeks, baby opossums are born. The tiny bee-sized joeys crawl into their mother’s pouch where they are protected and nursed for about 60 days. It is in the pouch that most of the joeys’ development takes place. At about 55 days the joeys finally open their eyes, crawl out of the pouch and cling to their mother’s back. The joeys ride along, learning from her the wide variety of foods to seek for their omnivorous diet that has earned them the reputation as one of nature’s sanitation workers! Their diet includes insects (including ticks), slugs, eggs, birds,frogs, plants, fruits and mammals as large as rabbits. They also eat human food and have been known to push over trash cans looking for leftovers. Opossums have a great need for calcium which they consume by eating animal bones.
Opossums are nocturnal mammals with enormous pupils which let in the dimmest light and long whiskers on the sides and front of their snouts which help guide their nightly foraging as they travel almost 2 miles through an area roughly 12 acres in size. Opossums are skilled climbers with opposable thumbs on their hind legs and a hairless prehensile tail that they use to anchor themselves in treetops to increase their reach for berries and other fruits. The tail is also used for carrying grass and leaves in a bundle when changing the bedding in its tidy den. Although opossums are often preyed upon by other nocturnal animals such as owls, foxes and bobcats, they are exceedingly resilient. If its loud hissing and the sight of its open jaws showing 50 pointy teeth does not deter a predator, the opossum will collapse to the ground with eyes open, mouth open and drooling, with its tongue hanging out. Its heart rate slows allowing it to lay very still as if dead, “playing possum” until the predator leaves. People think opossums might be rabid when they drool and hiss and carry on when threatened, but rabies in opossums is extremely rare. It may have something to do with the opossum’s low body temperature (94-97º F) making it difficult for the virus to survive in an opossum’s body. Opossums have partial or total immunity to the venom of rattlesnakes and other poisonous snakes.
It turns out opossums are allies in the fight against Lyme disease. From Rick Ostfeld, senior scientist at Cary Institute of Ecosystem Studies: “Possums, like many other small and medium sized mammals, are hosts for ticks looking for a blood meal. But opossums are remarkably efficient at eliminating foraging ticks. Several years ago, scientists decided to learn about the part different mammals play in the spread of the ticks and the disease. They tested six species — white-footed mice, chipmunks, squirrels, opossums and veerys and catbirds — by capturing and caging them, and then exposing each test subject to 100 ticks. What they found, is that of the six, the opossums were remarkably good at getting rid of the ticks — much more so that any of the others. “I had no suspicion they’d be such efficient tick-killing animals,” Ostfeld said. Indeed, among other opossum traits, there is this: They groom themselves fastidiously, like cats. If they find a tick, they lick it off and swallow it. (The research team on the project went through droppings to find this out.) Extrapolating from their findings, Ostfeld said, the team estimated that in one season, an opossum can kill about 5,000 ticks.
University of Michigan BioKids: http://www.biokids.umich.edu/critters/Didelphimorphia/
NH Public Television: http://www.nhptv.org/natureworks/opossum.htm#6
Science Daily: https://www.sciencedaily.com/releases/2009/12/091215202320.htm
Mass Audubon-Situations and Solutions/Opossums: https://www.massaudubon.org/learn/nature-wildlife/mammals/opossums/situations-solutions
Cary Institute of Ecosystem Studies: http://www.caryinstitute.org/newsroom/opossums-killers-ticks
Opossum by Tom Jackson
Backyard Jungle Safari Opossums by Ann Tatlock
Mother Nature Network: https://www.mnn.com/earth-matters/animals/stories/10-things-you-didnt-know-about-opossums
Opossum Society of the United States: http://opossumsocietyus.org/faq-opossum/
Paula Goodwin is a member of the Acton Conservation Commission who introduced WildAware with Acton Natural Resource Assistant Bettina Abe. WildAware is a program sponsored by the Town of Acton Natural Resources Department that began in September, 2015. The purpose of WildAware is to educate the community about the existence and habits of wild creatures, and the goal is increased community awareness of shared habitats. For information, call 978-929-6634 or send email to nr@acton-ma.gov.