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Posts Tagged ‘Virginia opossum’

yapok

The yapok or water opossum is a marsupial that ranges into Mexico and Central America.

Americans are an unusually insular sort of people. We fail at geography big time. Don’t ask the average American what the capital of Canada is.  Don’t tell tell us that Mexico City is the largest city on the continent.

“Because Mexico ain’t on our continent!”

That attitude even affects how we view nature.

When I was a little boy, I accepted without any question that North America’s only marsupial is the Virginia opossum.

It seems this claim is so widely-accepted that it is usually mentioned within the first sentence of any description of the species.

There is, of course, a big problem with this description. North America isn’t just the US and Canada.

This is North America:

North America

Yes. All that territory from Mexico to Panama is part of North America, and in those countries, there are multiple species of marsupials. Central America has 11 species. Mexico alone has has 8!

It is correct to say that the only marsupial in the US and Canada is the Virginia opossum, but it is geographical ignorance that only an American could conjure that says the Virginia opossum is the only marsupial found on the continent.

So when you see someone saying that Virginia opossums are the sole representatives of marsupials on this continent, realize that this person hasn’t thought through what he or she is actually saying.

Or is totally unaware that there isn’t continent between “North America” and South America.

There is also a subconscious racism at work, which sees only a community with Anglo-America as the true North America and casts aside that which lies to our south as being the other.

It may all be a silly little thing, but it grinds my gears.

And when we write about nature, we need to be more careful with our language.

 

 

 

 

 

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This week we had several visitors on the trail cameras. Keep in mind that one of these cameras has a messed up clock, so the time stamp reads that the video was taken in 2068. These cameras are pretty good technology, but they aren’t that good!

Let’s start small.  Here’s a white-footed mouse or a deer mouse:

Source.

I can’t tell whether it is a white-footed mouse or a deer mouse, which is hard enough to do in the broad daylight. These animals are in the genus Peromyscus, and although we call them mice, they aren’t closely related to the mice that originated in Old World.  New World rats and mice are more closely related to voles, hamsters, and lemmings than to house mice and Norway rats.

Then we got a light-colored opossum:

Source.

A good close-up of a melanistic gray squirrel:

Source.

And a large raccoon:

Source.

Because of the size of the raccoon, I am assuming that this one was a male. He was coming to inspect a pile of sticks and logs that I have anointed with weasel lure.

 

 

 

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Got this ‘possum in cage

It’s a little female Virginia opossum.

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The much ballyhooed prehensile tail:

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Old opossum

old opossom

I get opossums on the trail camera fairly regularly, and because I find them somewhat less interesting than other animals, I usually don’t post their photos on here.

This one, however, is kind of interesting because it has the features of a very mature individual. Now, keep in mind that Virginia opossums don’t live very long, even though they are about the size of a domestic cat. In captivity, their record longevity is a measly four years.

But this individual is at least on its second year.  The frostbitten ears suggest that it has survived more than couple of very hard freezes.

As opossums mature, they get a lumpy head profile.  When they are younger, they have a more collie- or borzoi-like head, but as they get up in years, this starts to change.

This opossum is the most primitive mammal north of the Rio Grande, and when I say this, I don’t mean that it’s primitive because it’s a marsupial. It’s actually a primitive marsupial, meaning that it looks very much like the earliest mammals that gave rise to all marsupials. Indeed, it is so primitive that the similarities between New World opossums and the West Indian solenodons are pretty striking. The two species of solenodon retain many primitive features of the ancestral placental mammals, and it would make sense that the primitive opossums and primitive solenodons would look somewhat similar to each other.

Beyond their taxonomy, there aren’t really that many amazing things about opossums. They don’t have very complex behavior.  There are claims of them having amazing intelligence that one can find online, but these clams are not born out in reality.

The thing is, you don’t have to be too smart if you can eat just about anything and reproduce by having dozens of offspring every year.

And even though they are primitive, natural selection has still worked its ways on their kind, but it’s just not change them as much as it has us, coyotes, or red kangaroos.

 

 

 

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An old opossum

This old opossum is a survivor. It looks like it even has a bit of frost bite on the ears from last winter.

old opossum 

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One ugly barn cat

Source.

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There’s a common statement on various websites related to opossums. It goes something like this:

“Opossums are not as stupid as people think. A study (or studies or tests) show that opossums are better at learning and discrimination showed them to be higher ranked than dogs.”

Okay. I’m going to call bullshit on this one.

Wanna know why?

I can’t find the study or test or any kind of peer-reviewed paper that says this.

And if I were a researcher making comparisons between the cognitive abilities of certain animals and the opossum wound up besting the dog, then I’d have very real questions about my methodology.

Here are the reason for my skepticism:

First of all, opossums have very small, very primitive brains. They are primitive mammals that retain much of the basal mammalian body type. They look very similar to basal placental mammals like the Cuban solenodon. Primitive mammals are unlikely to have many of the sophisticated cognitive abilities of more derived species, especially those that evolved to hunt cooperatively, like wolves and domestic dogs.

Secondly, no ethologist has recognized any sophisticated behavior in opossums. Opossums have been commonly kept as pets and as research animals for a very long time. They have been studied very closely, but no one is writing any great pieces of research on how opossums are able to reach such cognitive heights with such primitive little brains.

Now, there are many, many researchers looking into the cognitive abilities of dogs.  Studies have shown that dogs have very sophisticated social cognition, which they may have evolved through domestication. Dogs recognize the importance of human gestures, and they also know that when a person closes his or her eyes, the person cannot sense what the dog is doing.  There are dogs that respond to hundreds of words, and dogs can think abstractly.

If it were suddenly discovered that opossums could best dogs at these skills, it would be shatter almost everything we know about cognition in vertebrates. It would also fundamentally shift how we understand brain physiology, for an opossum’s brain is far more primitive and less complex than that of a dog.

So here’s my question to every site and book I’ve seen that makes this claim:

Where is the study that shows the impressive learning and discrimination abilities of opossums?

What’s its citation?

My guess is this study either doesn’t exist, or it is a simple methodology error in a multi-species comparative cognition study that the authors attempt to account for in the work.

And one study does not change the entire body of knowledge about a subject. It’s only when a particular study has a superior methodology that one can say it is paradigm shifting.

If this study does exist, it didn’t change the scientific community’s understanding of opossum versus dog intelligence.

If it did, you’d be seeing researchers working with large numbers of opossums to see how their cognitive abilities work.

And that’s simply not the case.

The old saw that states that extraordinary claims require extraordinary evidence certainly applies here.

And as far as I can tell, this is nothing more than an internet rumor that somehow grew legs.

 

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