Posts Tagged ‘Virginia opossum’

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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I got a nice photo of some opossum tracks this afternoon.

The front foot track is the one that looks like a large asterisk.  It’s on top.

The hind foot track is the one that looks like an open hand. The hind feet have opposable thumbs that are used to grip branches. They can also grip with their front feet, but their opposable thumbs on their hind feet are unique among animals in this part of North America. No other native species has this feature.

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New GEICO commercial.


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"I am so smart. I am so smart. S-M-R-T. I mean S-M-A-R-T!"

The internet has proven a blessing for transmission of information, but it has also proven to be a source for transmitting urban legends and unsupportable lore.

Like Obama’s birth certificate controversy and the so-called 9/11 truth movement.

One of the most bizarre urban legends that I’ve seen repeated time and again is that Virginia opossums are smarter than dogs.

If one does a Google search of that phrase, “opossums are smarter than dogs,” one will come across different sites that say “studies” or “a study” showed that opossums performed better on a learning and discrimination test than dogs.

Study or studies are words that give on credence to such a position.

However, this study, if it does exist, flies in the face of Occam’s razor.  Occam’s razor or the law of parsimony state that when one comes up with a hypothesis, if one uses the fewest number of new assumptions in the model, the greater the chance of being right.

Occam’s razor is also useful in interpreting the results of the study. Paring back assumptions after the results of the study are available is more likely to bring about the correct interpretation than a wrong one.

And if one winds up interpreting the result of any study that points to opossums being smarter than dogs, then we have a big issue with Occam’s razor.

The new assumptions must be running wild.

We know lots of things about canine cognition. One of the most important recent findings is that domestication may have enhanced certain cognitive abilities in dogs. It is easier for them to learn from human gestures than it is for wolves that have been socialized to to people.

Some of these cognitive abilities, such as responding to a human pointing, are apparently present in dogs but are absent in great apes. This is not to say that dogs are smarter than the great apes. Rather, it suggests that domestication may have enhanced some of their cognitive abilities.

The results of these studies have been confirmed time and again, though there is still some question if responding to these gestures is actually innate. And there was one study in which the wolves outperformed the dogs.

But in general, the results show that dogs are able to respond to human gestures and socialized wolves are less adept at doing so.

So if these results get confirmed time and again, how can one study prove the opossums are so much smarter than dogs?

It would have to be a convincing study.

It would have to be groundbreaking.

And you’d likely be able to find it within less than a half hour’s search on Google Scholar.

Guess what?

It’s not.

Try looking for this study on Google Scholar.

You won’t find it.

In fact, I cannot find it right now, though I have actually seen it.

It was a test based upon having various animals locate food based upon “remembering”  where it was.

Well, there is a little problem with this sort of study. Virginia opossums have a very keen sense of smell, the researchers probably didn’t control for that issue enough. Its brain possesses a massive olfactory bulb, and it is through its sense of smell that it is able to find food in its nocturnal ramblings.

A study that didn’t control for the opossum’s very good sense of smell is hardly going to be definitive about opossums being smarter than domestic dogs.

In fact, you can’t make that case at all.

Further, there is no evidence that Virginia opossums possess very sophisticated cognitive skills at all.

They aren’t social animals, and their body language is rather simple.

Dogs have very complex social signals, and with all of these studies showing that they do have rather advanced cognitive skills, how can one honestly say that a single study based upon remembering where food is located suggest that the opossum is smarter?

Now, there are few things I’d like to discuss about opossums and intelligence.

If someone can show me a study of opossums doing the complex behaviors that dogs do, I might drop my objections.

My guess is that no one has a pet opossum anywhere that can do the things that dogs do, and this study is quoted for no reason other than to uplift the lowly opossum in the public mind.

We do tend to think of opossums rather poorly.  They don’t have any charisma at all, and if they were endangered, it might be hard to get people to want them to be preserved.

However, is it worth posting unscientific information with appeals to the authority of a “study” or “studies” to make the opossum into something it clearly isn’t?

I don’t think saying that opossums are smarter than dogs actually does them much justice.

Most people who hear such claims are more likely to laugh at them.

And if they knew how unscientific the evidence for this claim actually is, they would never you seriously.

So it might make people feel good when they say opossums are smarter than dogs, but it’s a bizarre claim for which the bulk of the scientific evidence shows otherwise.

The supposed genius of the opossum is one of those pieces of disinformation that has been spread up and down the internet that it might be nearly impossible to disabuse people of such delusions.

If you think opossums are smarter than dogs, then why aren’t they a model organism for cognitive studies?

They aren’t.

Modern cognitive studies mostly look at dogs, rats, and primates.

If opossums were so unusually brilliant, they really would be studied a lot more.

They have very primitive brains for mammals, and if they possessed anything like the intelligence “teh internets” say they have, they would be studied very closely. How could an animal have such advanced cognitive skills with such a little primitive brain?

The answer is they don’t, so no one is studying them!

Their lack of higher intelligence is exactly what we expect for animals with these brain structures.

And that’s why modern scientists don’t waste time trying to explore the opossum’s cognitive processes.

It’s just not that useful.

Primitive brains and lack of intelligence are two traits we expected to see.

To deny these facts is to court foolishness.

And if these people have 50 “rehabilitated” opossums in the basement, they are definitely fools!





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Great interview here:


Didelphis opossums include the Virginia opossums. Opossums of this genus can eat cane toads without dying.  Mexico and Central America are part of North America, so it is in error to say that Virginia opossums are the only species found in North America. They are the only ones found north of the Rio Grande.

Yes. It’s a terrible idea to introduce Virginia opossums to Australia to control cane toads.



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From Hunter-Trader-Trapper (1902):

I am very much interested in the domestication and cultivation of the’ opossum and skunk, especially the latter. Mankind is rapidly pre-empting the inhabited territory of the world and the domain of wild animals have rapidly become extinct and many more are rapidly disappearing from the face of the earth. Hunters and trappers are penetrating the wildest and most forbidding parts of the earth in quest of furs, while farmers and boys all over the country are robbing the skunk and opossum of their furry coats that “our fair lady” may have warm neckwear. Very few people have any idea of the immense amount of this “second hand” clothing there is worn thruout the world. It is my opinion that furs in the future will rapidly become scarcer and therefore higher. Carnivorous animals have a natural antipathy for man and can rarely be domesticated. The skunk and opossum are carnivorous to a certain extent but will eat a great variety of foods. The opossum is a great vegetarian and will eat all kinds of fruit. The skunk is a dear lover of sweet corn, sweet potatoes, bread, melons, etc. The fact is these animals are easily kept and are also easily tamed, especially the skunk. The skunk is as easily cared for as the ferret, and there is a ready market lor his fur, while to sell the ferret you must advertise for a buyer. The skunk is one of the three animals of the world that furnishes a naturally black fur. The black house-cat and the black bear are the other two [LOL, Great naturalist there!]. This is one secret of the great value set on the fur of the black skunk. I do not think the cultivation of skunks will ever be overdone. I would very much like to read the experience of others who have tried or who are trying the project of raising these animals. I made my third shipment of furs for this season Feb. 7, 1903. It consisted of 15 skunk, 15 muskrat, 17 opossum, 3 mink and 2 house-cats. My check for above was a beautiful little piece of paper worth $31.45. This puts me near the $100 mark for this year. I have on hand about $15 worth of furs since I shipped. I expect to make about two more shipments this year.

Lee S. Dick

I’d like to know where he got the info on black fur. Um, in case you didn’t know, it’s bit wrong.

But apparently at one time, there was a great market for cat fur!

I don’t know what became of this domestication attempt. I know that striped skunks can breed in captivity, and they come in several fur farm color morphs. Some states that allow pet skunks require that one be of one of these morphs, just so that the authorities know for certain that any pet skunk is captive-bred.

I don’t think opossums have ever been propagated in this fashion. I’ve never heard of an opossum fur farm– probably because the fur itself never was all that valuable.

My guess is Mr. Dick’s venture didn’t go very far. Even if skunks are easy to breed in captivity, they have to be descented, which is a cost that exists across an entire breeding operation. I know that ferrets normally are, but I don’t think descented ferrets necessarily had to make up the bulk of the early domesticated population. With striped skunks, one would have to descent them. It’s just too much of a hazard to deal with an animal that squirt nastiness into your eyes every time it gets a little miffed.


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