What makes Opossums so cool?

You have seen the meme’s floating around telling you to love the Virginia Opossums because they eat ticks. They do and it is most certainly an endearing quality, but it  is not the only thing that makes Opossums so cool.

The teeth

Opossums have the most teeth of any North American mammal giving them their characteristic smile.  These teeth help these omnivorous scavengers devour road kill and other cadavers bone and all. This bone crunching ability helps them meet their very high nutritional requirement for calcium.

The Tail

Opossums have a prehensile tail. They use this tail as an aid while climbing. Contrary to popular believe they don’t sleep hanging upside down from their tail and being picked up by their tail is painful.

 

 

The Feet

Opossums have opposable thumbs on all 4 feet. Again and adaptation to help them climb.nhes0lohqlen7bfvbzsvow_thumb_7e08

The Pouch

Opossums are North America’s only marsupial. This means they carry their offspring in a pouch on their belly like a kangaroo.

20-30 very tiny babies are born after only a 13 day gestation. They crawl their way to the pouch and locate a nipple which they swallow. They stay in the pouch for about two months after which they start leaving the pouch intermittently and often simply ride on the mothers back. They wean after 3 months.

It is important to check on recently killed opossums you see on the road during the summer months. Often if the female gets killed the babies in the pouch who are cushioned by her body survive. If you find any babies who are still alive please contact your local wildlife custodian, SPCA, Humane Society or Animal Control for help.

Although both male and female have a pouch (much like men have nipples) it isn’t difficult to figure out the gender. The testicles of a male opossums have a blue colour to them and are hard to miss.

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The Immunity

Opossums enjoy dining on snakes and as a result evolution gave them an immunity to a large variety of snake venoms. We don’t have many venomous snakes around Ontario, but opossums are a fairly recent arrival in our province and brought their venom immunity with them from the Southern US.

Despite their recent arrival they are not an invasive species as many believe them to be. They arrived here on their own accord and are not a human introduced species. This makes them now a natural part of the mammals living in our province.

The Body Temperature

Opossums have a significantly lower body temperature than most other mammals. This is what makes them less likely to contract rabies. They simply aren’t warm enough for the virus to survive.

It is however not impossible for opossums to get rabies as there have been a couple of recorded cases.

The lifespan

The average lifespan of an opossums is 4 years. This isn’t very long and certainly much less than most people expect.

Playing Possum

This is an involuntary physical response to danger which they share with fainting goats. If they think their life is in danger an opossum with go stiff and roll on their side. Their body bloats and starts giving off a putrid smell resembling being dead very closely. After some time passes they eventually will regain consciousness.

Despite the toothy grin they display biting or attacking is not the preferred defence, playing dead is.

The EPM

Opossums are the definitive host for the EPM protozoa and if an infected opossum’s feces end up in horse feed can cause an unvaccinated horse to contract EPM. It is therefor best to keep opossums away from horse barns.

The frostbite

As more recent arrivals in our great province the Virginia Opossums has yet to evolve into being able to withstand our frosty cold winters. They create dens in which they sleep during the day and they are predominantly active during the night.

However when it is well below zero their naked feet, ear and tail easily freeze, so they often chose to stay in their den to prevent frostbite.

If the cold spell goes on for an extended period of time they have the option of freezing to death or starving to death.

Every year we admit a lot of opossums with frostbite. I hope evolution catches up soon and gives them nice furry feet, tails and ears.

 

 

 

 

 

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Why bird feet don’t freeze

Many people have bird feeders out and get enjoyment out of seeing birds in their back yard during the winter months.

If you pay attention you will have noticed that birds are well covered with a thick layers of warm feathers with the exception of their legs and feet, yet somehow these naked, spindly little legs and feet don’t freeze.

Birds actually have a nifty heat exchange system in their legs called Rete Mirabile which helps them prevent freezing. They share this system with some other animals such as fish and some mammals such as sloth and lorises.

In bird feet the arteries run really close to the veins causing warm blood heading from the body to the legs to warm the cooler blood flowing back to the body. This system reduces heat loss and is further enhanced by the arteries which relocate from a position closer to the skin during the summer more to the center of the leg during the colder winter month.

Bird lower legs and feet don’t contain muscles (just tendons). This causes the legs and feet to need very little energy allowing for reduced blood supply.

When it is really cold however even this system needs a little help and you will see birds sitting down with their feet tugged up into the downy feathers on their chest/belly to prevent their feet from freezing.

Canada Goose Sitting down to prevent cold feet

During severe cold spells we often receive calls from people who think waterfowl are frozen to the ice which most often is simply a case of a waterbird sitting on the ice using its feathers to keep its feet warm. They are often reluctant to move because exposing their naked feet to the cold can cause them to freeze, much like our fingers and toes.

 

Many healthy birds, particularly waterfowl spent a lot of time preening ensuring their plumage is perfectly oiled. The oil is produced by their uropygial gland which is located at the base of their tail. The oil repels water making it that the birds don’t get wet, but it also prevents them from freezing to the ice.

Waterfowl who are not healthy and therefore have neglected their plumage will often appear wet. These are birds who need help right away. In those causes don’t hesitate to contact you local SPCA, Humane Society, Animal Control or Authorized Wildlife Custodian.

Some of the birds of prey have adapted by growing feathers further down their legs and sometimes even feet reducing the exposed skin portion of the leg. This of course also helps reduce heat loss.