I’m going to Chicago this week for my sibling’s college graduation! I’m very excited.
Now, cities typically aren’t the first place you think of when you think of thriving wildlife. But many critters have found ways to thrive in urban environments, and Chicago is no different.
So, in honor of my sibling’s graduation, let’s talk about an animal you can find in Chicago: the Virginia opossum.
The Virginia opossum (Didelphis virginiana; commonly called just ‘opossums’) is one of over 100 different opossum species living in North and South America and the only species found in the United States and Canada. In fact, it has the distinction of being the northernmost marsupial in the world! They are cat-sized (2.5 feet or 76 centimeters long from nose to tail) with white and gray fur and a long, hairless tail that is over a third of its body length.
As far as the name goes, the story is that ‘opossum’ comes from the Algonquin name for the creature, ‘aposoum,’ or ‘white beast.’ It was first used by Captain John Smith in 1608.
Oh, and just so you know: a group of opossums is called a passel!
Opossum vs. possum
Let’s clear this up first: is it ‘opossum’ or ‘possum’?
The answer is…complicated.
In the United States, it is very common for people to call Virginia opossums by the name ‘possum.’ However, we should be careful here! Possums are another animal species that live in Australia and are more closely related to kangaroos than opossums.
However, possums and opossums are somewhat related – both are marsupials (like kangaroos and koalas). And unlike Australia, which has many different types of marsupials, opossums are the only marsupials found in the New World.
What’s up with that tail?
A common myth is that opossums can hang upside down by their tail. This is somewhat true – opossum tails are prehensile. However, they can really only hang upside for short periods of time. Opossum tails are much more suited for maintaining balance as they move through the trees or carrying nest-building materials like leaves and grass.
In addition to this prehensile tail, opossums have opposable ‘thumbs’ on their feet called hallux. These hallux help opossums keep a good grip as they climb.
Here’s a fun story: people used to think that opossums bred and gave birth through their noses. This legend arose because a) male opossums have a forked penis, and b) female opossums nuzzle their pouch right before the joeys (baby opossums) appear. Given these facts, the logical explanation was that males impregnated females through their nostrils. Then, the females sneezed the joeys out into their pouch.
This is not how opossums make babies.
Yes, males have a forked penis, but they don’t put it in the female’s nostrils. Instead, they breed like other mammals, with their penis working nicely with the female opossum’s forked reproductive tract.
Regarding the sneezing, remember that marsupials have young that are little more than embryos when born. After birth, the joeys must travel across their mother’s abdominal fur and into their pouch. However, since they are so small (about the size of a dime), this is hard for us to observe. From our point of view, we would see an opossum with an empty pouch one day, then see her with her nose in her pouch with tiny joeys the next day. While sneezing could be one explanation, the truth is that the female has her nose in her pouch to clean it or soothe her swollen teats. We simply missed the joeys making the journey into the pouch.
As marsupials, joeys spend the first part of their lives in their mother’s pouch. They’ll remain in the pouch for 2 – 3 months, with their eyes only opening when they’re 55 – 70 days old.
As the joeys begin to get too big to stay inside their mother’s pouch full time, they transition to riding on her back. Their mother will carry her joeys from place to place as she searches for food for herself. This also serves as a prime time for the joeys to learn survival skills like what food is good to eat and how to avoid predators.
And if a joey falls off or becomes separated from its mother, don’t worry – they’ve got ways of reconnecting! A joey will make sneezing sounds to call to its mother, and the mother will make clicking sounds in return.
Virginia opossums are weaned at around 3 months old and can survive by themselves by the time they are 5 months old. At this point, they are 7 – 9 inches long from nose to rump and are ready to strike off on their own.
Playing dead is so incredibly linked to opossums that we even have a phrase: playing possum.
When opossums are threatened or scared, they will ‘play possum’ and appear sick or dead. Teeth are bared, saliva foams at the mouth, and a smelly fluid is secreted from the anal glands. The opossum is, by all appearances, dead; the hope is that predators will lose interest and leave it alone.
The word ‘play’ in ‘playing possum’ suggests that the opossum knows what it’s doing and is playing dead on purpose. However, research indicates that playing dead is actually an involuntary and automatic action. The opossums don’t mean to do it but are instead fainting from fright.
Here’s another fun fact: Virginia opossums have more teeth than any other North American land mammal. Their mouths contain 50 teeth! Other North American mammals have at most 6 upper incisors, while Virginia opossums have 10.
They use all of these teeth to eat (obviously). Virginia opossums are scavengers as well as omnivores, and they play an essential role in cleaning up our backyards.
For instance, opossums may eat ticks. This is hugely important for protecting us and other animals from the spread of tick-borne diseases like Lyme disease. (I should note that the idea that opossums are basically tick vacuum cleaners does not appear to be true!)
In addition to ticks, opossums will use their long and powerful snout to sniff out all sorts of food, from fruits, insects, and venomous snakes to carrion, roadkill, and garbage. Clearing out rotting food and dead animals helps keep things clean. Opossums even eat animals that we consider pests – cockroaches, mice, and rats.
How do they eat all of this without getting sick? It turns out that Virginia opossums are incredibly resilient.
They are highly resistant to rabies because they have a lower body temperature than other mammals. Their body just isn’t suited for the rabies virus to survive. And, because they rarely get rabies, they rarely transmit it to humans or other animals.
In addition, Virginia opossums don’t have to worry about getting bit by snakes. They are basically immune to the venom of rattlesnakes and pit vipers.
So even though opossums may look gross, they are actually helping keep our world clean! And because they spend a lot of time grooming themselves with their tongues and paws, opossums are very clean creatures.
If you see an opossum out in the wild, the best thing to do is to leave it alone and let it do its own thing. It’s just being a helpful neighbor!