The Tasmanian Devil I guess, because all the other marsupial predators are dead. I’m guessing for monotremes it’s the Platypus, pretty limited competition there.
“Although many people think opossums are not the sharpest knives in the drawer, there are several areas of intelligence in which they soar. For one, they have a remarkable ability to find food and to remember where it is. When tested for the ability to remember where food is, opossums scored better than rats, rabbits, cats, dogs … but not as well as humans. They also can find their way through a maze more quickly than rats and cats.”
Interestingly, while marsupials have usually been assumed to be less intelligent than placentals, it turns out there is no systematic difference in brain size. Most of the average difference is due to the inclusion of the big-brained Primates among the placentals, and if they are removed, the difference largely disappears.
The marsupials with relatively small brains are the kangaroos and bandicoots. However, the small carnivorous dasyures have brains larger than placentals of the same size.
Interesting, monotremes, particularly echidnas, have brains that lie above the regression curve of brain vs body size for placentals.
I once came upon an opossum in the barn, chowing down on cat food back when I still fed cats out there (and part of the reason why I stopped leaving cat food out other than in the house.)
It tried, reasonably sensibly, to run away from me. It ran almost immediately into the side of a box full of something heavy – and just kept trying to push through the side of the box, unsuccessfully, while I got a bucket from elsewhere in the barn and then put the bucket down over it, trapping it.
(I then slid something under the bucket, upended the assembly, and carried the possum in the bucket out some distance into the field, where I emptied the possum out of the bucket.)
I can’t imagine any other creature not having dashed around the side of the box while I was getting the bucket. The possum just kept trying to power through it.
It may, of course, not have been the brightest example of its species.
You didn’t need a bucket, just grab it by the tail (closer to the tip than to the base.) It can’t turn itself far enough to bite you. (Though I have seen young ones try to climb their own tail hand over hand while I hold them.) and they are so easy for me to catch because–much like yours–they get in a corner and just stop. And take their time getting there.
Not koalas. They have among the smallest mammalian brains, about 0.2% of their body mass. Brain ratio is a very weak correlation with intelligence, nevertheless they appear to be a species that does not require much intelligent action.
No, they’re not smart, so the question is probably better framed as ‘which is the least abjectly stupid marsupial’.
The ones most commonly kept as pets from birth - wombats and wallabies - can be house-trained to some extent, but they are stubborn and don’t take instruction well.
I’ve heard about someone who cared for a dasyurid, I think aTiger Quoll, which is a beautiful carnivore about the size of a small cat, that thought it was a great companion and smart enough to get into things and generally cause mayhem.
This isn’t surprising, since they are the marsupial equivalent of sloths, and sloths are among the placentals with the lowest ratio of brain to body weight. It doesn’t take much brain power when you spend all your time surrounded by your food supply. But koala stupidity is due to their diet, not to the fact that they are marsupials.
The article I cited suggests that they’re no stupider than the average placental (excluding primates).
That aligns with the article I cited, which found that diprotodonts, which include wallabies, wombats, and koalas, are among the least brainy marsupials, while dasyures are brainier than similar-sized placentals.
I was wondering about attempts to tame marsupials.
People seem to like smarter animals to tame (but not always). So maybe which ones people have tamed might indicate which ones are smarter.
Some Googling right away lead me to sugar gliders. Being able to glide means a pretty decent real-time thinking ability. They are quite social, which also means a more advanced brain.