Tuesday, February 1, 2011

Non-hibernating Opossums


It is true: Opossums do not hibernate.  Unfortunately for them, their feet, ears and tails have no fur so they frequently suffer from frostbite in our northern climate. You'll spot them in alleys, along the streets and especially under bird feeders.

Officially named "Virginia Opossum," opossums have gradually made their way northward and are now even found in Canada.  In fact, most literature is still outdated and shows the northern range of opossums to be just north of the Twin Cities.

I find it fascinating that there is one striking difference between our opossums up here and their southern relatives: the southern opossums are furless on their bellies, probably to help them keep cool during the summer.  Our opossums? They have furred bellies.  I think of it as actually being able to watch a species evolve to better their survival odds. How cool is that?

Unfortunately for opossums, they don't survive long in the wild: 3 years is considered maximum life expectancy. They are slow moving, and as noted above do not hibernate so they struggle through the winter.  And, even with the most number of teeth of any North American mammal (50!), they still fall heavily to predation. They really do play 'possum, rolling onto their sides and playing dead.  Alas, this makes them sitting ducks for coyotes, fox, dogs, wolves and other larger mammals.

Young opossums are preyed upon by owls, hawks and even squirrels.  In my opinion, this is when opossums are at their very cutest stage:


The opossum is unique in two other ways: 1) It's the only marsupial in North America. The female gives birth to 9-16 babies, but only has 13 teats in her pouch. Babies who do not immediately latch on to a teat die. And, 2) the species-standard number of teats is 13, an odd number, as opposed to an even number.  The majority of mammals have an even number of teats as the standard, although individuals often have an odd number.

One of the most impressive things I learned when first working at WRC is that people will actually stop at the side of road to check the pouch of a roadkill opossum.  It's amazing to me that people take the time to rescue these tiny babies - no wonder Minnesota has such remarkable parks and wildlife, it has great stewards. To be honest, the thought had never crossed my mind to stop and see if there were live babies in an opossum's pouch. 

Opossums are nocturnal as a general rule, but it's not unusual to see them out in the early evening hours or early morning. In fact, this post was prompted by an opossum enjoying spilled birdseed in the middle of the afternoon today. 

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