Farm Horizons, August 2012
Minnesota’s marsupial invasion
By Ivan Raconteur, Staff Writer
What was once a rarity in most of Minnesota has become much more common in recent years as the Virginia opossums are making the state their home in increasing numbers, according to the Minnesota Department of Natural Resources (DNR).
Opossums (or possums, as they are commonly called, have lived in extreme southern Minnesota for about a century, but they have been expanding their territory northward into new areas in recent years. They have even been seen in northern Minnesota.
The strange looking creatures North America’s only marsupial, and are related to kangaroos, koalas, and other marsupials that are native to Australia. They have been around for at least 70 million years and are among Earth’s oldest surviving mammals.
Opossums can be easily identified by their distinctive ears and long, hairless prehensile tails.
They can wrap their tails around branches, and even hang from their tails for a short time. Opossum has opposable hallux. A hallux is like a thumb. The opossum’s “thumbs” are on its rear feet. The hallux helps it grasp branches when it climbs.
Virginia opossums are relatively small, about the size of a house cat. They generally weigh from 4 to 15 pounds and measure about 3 feet from nose to tail. Males are larger than females.
Virginia opossums are generally grayish-white in color, but can be darker gray or almost black. They may have white faces and pink noses.
When threatened, opossums may click their teeth, growl, or screech.
The Virginia opossum’s range was once limited to the southeastern part of the US, but they now live in a much larger territory, including all but the northernmost part of Minnesota.
According to the DNR, opossums mate between January and May, and females may bear two litters of six to 20 young each year. They carry their young in their pouch for two months or longer until the young opossums are ready to become more independent.
When they first emerge from the mother’s pouch, young possums spend much of their time riding on their mother’s back.
Opossums eat almost anything, including fruit and grain, eggs and young birds, worms, snakes (possums are resistant to snake venom), insects, and even garbage and carrion.
Because carrion often i ncludes road kill, many possums are killed by vehicles as they scavenge for food on roadways.
Their predators include dogs, bobcats, coyotes, foxes, hawks, and owls.
Opossums can be found in woodlands and agricultural areas across most of Minnesota. During daylight hours, they spend much of their time under cover in hollow logs, dens, brush piles, or under buildings. They tend to prefer wet areas such as marshes, swamps and streams.
Trappers harvest 2,000 to 8,000 of the fur-bearing creatures in Minnesota each year, according to the DNR.
Opossum, like badgers, can be hunted from late October to mid-March without limits.
If cornered, an opossum may lie still and secrete a foul-smelling scent. This is commonly known as “playing dead” or “playing possum.”
Their hairless ears and tails are susceptible to freezing, which is why they are not found in the northernmost part of the state, where frigid temperatures are common during the winter months.
According to a March 2011 Minnesota Public Radio news story by Jeff Jones, biologists say opossum don’t really compete for food or territory with other animals and aren’t known to significantly harm crops or spread disease with one exception.
Opossum carry a disease that can cause a neurological condition in horses called equine protozoal myeloencephalitis.
According to the MPR story, “The more possums you have, the more likely you are to have horses exposed,” says Stephanie Valberg, Director of the Equine Center at the University of Minnesota’s college of veterinary medicine.
The condition is only harmful to horses, and is spread when horses eat food that’s been in contact with opossum feces. Valberg says the latest research shows most exposed horses never exhibit symptoms of the disease, and those that do probably have comprised immune systems to begin with.