Why are opposums successful compared to other marsupials?

Marsupials are generally failure when compared to placentals. They got out-competed and became extinct in continents like Asia. In South America they got wiped out when the placentals arrived except for some species of opposums. Australia due to its isolation became their safe haven.

But the Virginia Opposum is one single exception. Not only it survived the onslaught from North America when the land bridge was created, it managed to migrate north into North America. They seem pretty abudant.

I’m wondering about the reason for this “exception”. Maybe it’s because of lack of placental competition in the same niche, you know the Bering landbridge has always been cold and dry so many placentals from Asia who would otherwise be able to colonize America are not able to. Mongoose seem to be a potential competitor for the opposums, and the Old World monkeys too, who were barred from the Americas due to the extreme north location of the land bridge.

Many will argue that point.

But the possum will eat anything, is a fast breeder, not eaten by as many things as rats are, and happy to hang out with humans.

Good answer plus a few more things. Breeds at a youg age, has exceptionaly large litters. Young can take care of themselves at a very young age. I also suspect rapid breeding rate and large litters give it the ability to quickly adapt to any particular local conditions it has to deal with as evidenced by it’s large range and varied habitats. I live in a busy city where oppossum sightings at night have steadily increased over my 65 years yet road kills seem to have decreased telling me that they have geneticaly developed a shyness of cars.

Not an answer but possibly related. When I was growing up on the western side of the PNW, VOs were a common site, live and especially as road kill. Suposedly they were brought here in the early part of the last century by SE migrants, as pets (!) this guvmnt website says, but word on the street was that they were brought and set free to serve as a self-renewing food source. In any case, over more recent decades, the possums have, at least by my casual amateur observation, dwindled substantially. This has been accompanied by an equally noticeable rise of raccoons.

Their ability to play dead has been very successful for them. The Geico geecko is quite worried that possums will replace him, and the cavemen are nearly extinct. Hisss!!

Untrue, as has been demonstrated in previous threads on the subject.

There is no evidence that their disappearance in Asia and North America was due to competition from placentals. In addition, recent evidence indicates placentals may have been present in Australia before the arrival of marsupials (Ausktribosphenos nyktos and Bishops whitmorei in the early Cretaceous) or about the same time as they arrived (Tingamarra porterorum in the early Tertiary). If so, one could just as well argue that marsupials outcompeted placentals in Australia and caused their extinction there.

This is flat-out wrong, as has previously been pointed out to you (but you continue to repeat it anyway). The borhyaenids became extinct *before *the arrival of most placental carnivores after the Panama land bridge was complete. They were not wiped by placentals.

No, it’s not the “one single exception.” It’s the only species that colonized temperate North America, but another 13 species of opossums occur in tropical North America. Many of them are common and successful and do fine in the presence of placentals.

Besides this, opossums are very diverse and successful in South America despite the presence of many placentals. There are more than 110 species that fill a variety of niches, from generalized omnivore like the Virginian opossum, to insectivores, frugivores, carnivores, and even the fish-eating Water Opossum. There’s no evidence that placentals are superior competitors to these species.

As for why the Virginia Opossum is the only species that has colonized the temperate zone, it’s probably tougher for groups of tropical origin to colonize the temperate zone than vice versa. Placentals of South American origin have shown no better ability to colonize temperate North America - the only contemporary ones being the Nine-banded Armadillo and the North American Porcupine. The placental New World monkeys have failed completely to colonize the temperate zone.

Many South American marsupials live in temperate conditions in southern South America and the Andes, so it’s not that they as a group lack the ability to adapt. It’s just that the potential colonists in northern South America and Central American are tropical species.

So, if it is not a matter of being outcompeted by placentals, why is it that there are no marsupials in Eurasia or Africa, none apart from opossums in the America’s, but all sorts in Australia?

I didn’t know that the North American Porcupine was originally a tropical species.

Most likely chance. On a global scale, there are essentially three separate “experiments” regarding the co-existence of placentals and marsupials. Eurasia, Africa, and North America (the “World Continent”) have been connected intermittently through most of the Tertiary and so can be considered one experiment. The two others are the island continents of South America and Australia (South America having been isolated until about 4 million years ago). Assuming both groups were present during the Cretaceous on all the continents, on the World Continent the placentals won out, in Australia the marsupials did, while in South America the two groups coexisted by filling different niches (marsupials as carnivores/omnivores, and placentals as herbivores). So the three different experiments yielded all possible outcomes. There’s no evidence that placentals will deterministically outcompete marsupials due to any inherent superiority.

They belong to a group called the hystricomorph rodents, which includes the Old and New World porcupines, capybaras, agoutis, chinchillas, and a bunch of others. They apparently originated in Africa, and colonized South America by rafting across the Atlantic in the Oligocene. (The New World primates came the same way.)

There are many species of porcupines in South America, which unlike the northern one have prehensile tails.

You are pretty delusional to say the best. They are all small-sized and in case you haven’t noticed they are in the same group, the opposums. Placentals are much more diverse there, rodent species in South America alone are more diverse than the opposums. If you don’t recognize that, then I cannot see how you can even be the least subjective because the evidence is just so obvious. You seem to be extremely sensitive when it comes to supeririority and stuff, why are you so scared huh, don’t extend your politcal belief into the natural world if that’s the case.

And BTW you just derailed my original post, of all people you should have known better?

It’s “opossum,” by the way.

Actually, they don’t all belong to the same group. There are three separate orders of marsupials in South America, the Didelphimorphia, Paucituberculata, and Microbiotheria. While they are all commonly called “opossums” they are not very closely related to one another.

So what? That doesn’t mean that placentals are competitively superior as a group. Ecologically, since the opossums are mainly carnivores/omnivores, the most direct comparison is to the Carnivora. Opossums are more than three times as diverse as the Carnivora in South America.

Your original post was based on the entirely false premise that “marsupials are failures compared to placentals.” You can’t include such statements in an OP and not expect them to be addressed.

Only on Tuesdays and Fridays. :wink:

Thanks for recognizing that I am not “the least subjective.”

Objectively, there is no “obvious” evidence that placentals as a group are superior to marsupials.

I was unaware that you viewed this as a political rather than a scientific argument. What, are the placentals supposed to be capitalists and the marsupials socialists? (Maybe the monotremes are anarchists…)

In fact, your viewpoint on the inferiority of marsupials is very much a nineteenth century one. More modern evolutionary thought doesn’t look at them that way.

Um…griffon? Colibri actually IS a biologist, and one of the most knowledgeable posters on the board as far as the subject goes. I don’t think that you’re going to get anywhere twitting him about not knowing what he’s talking about, since pretty much everybody who’s been here longer than a year or so knows that he KNOWS what he’s talking about.

Too bad I’m not one of those mindless people who kow-tow the so-called “autorities” or “experts” or whatever without a second-thought. Doesn’t matter what job he does, just because someone has some degree does not make his opinions factual or unbiased. I for one consider myself more knowledgeable than him and I don’t need any “confirmation” or endorsement like you just gave to him. This is the key difference between those ignorant masses and the true enlightend people.

Don’t true enlightened people know how to spell “enlightened”?

Is spelling it “opposum” supposed to indicate what an independent thinker you are? Fight the Power! :smiley:

Your position is quite obviously not based on an objective evaluation of the evidence (especially since you don’t appear to know much about the actual evidence). As I said, it is very much an artifact of outmoded nineteenth century evolutionary views, in which there was a linear progression from lower to higher forms. Marsupials were regarded as a sort of “half-mammal” that hadn’t quite made the grade compared to the “true mammals,” the placentals. This is reflected in the names given to the groups by Thomas Huxley in 1880, the Metatheria (“almost-beasts”) and the Eutheria (“good-beasts”).

It was assumed that marsupials represented an evolutionary stage in the progression to placentals, and that placentals had marsupial or marsupial-like ancestors. In fact, fossil evidence has shown that the two groups are of similar antiquity, and that one did not evolve from the other.

Far from showing you are “enlightend,” your opinion just shows that you are stuck in a mode of evolutionary thinking that has been obsolete for decades.

Trust me, I know about evolution way more than you do. And marsupials being inefficient to placentals is not some idealogy, it’s a simple fact. You obviously ignore mountains of evidence in favor of your equalitarian view of the natural world, which I think shows how poor you are as a biologist as you shape your opinions around your ideology.

I don’t really want to crawl up Colibri’s butt here, but the man is an actual biologist! He WORKS IN THAT FIELD! I trust him to know what he’s talking about more than one of this year’s Junebunnies with no discernible credentials in the field.



May I ask where exactly you acquired this comprehensive knowledge? And why you don’t show any evidence of it in your posts?

If it’s a simple fact, prove it. You got demolished in your last thread on the subject.

Again, you’re the one who seems to think this is some kind of ideological issue. Because of their reproductive systems and physiological traits, marsupials may be superior to placentals in some circumstances and not in others. But you can’t make a blanket statement that they are intrinsically inferior.