Which mammal is generally recognized as the least intellectually adept?
I’m not trying to make this a value judgment as each animal is as evolved and adapted as it needs to be to survive. However, in that context which mammal generally shows the fewest indicators of what we humans interpret to be “intelligence”.
Well, if we use the Brain weight:Body weight ratio, the hippotamus isn’t looking too smart.
The blue whale and other plackton-filterers also have a tiny brain vis a vis its size. Strangely enough, their fish eating cousins, the orcas and dolphins are extremely smart by any measure.
generally recognised - stupid cows? i mean, even on PETA’s website, the best they can say about cows are that they are able to press a button for food. even goldfish can do that, and more. whatever it is, the likely candidates would be one of the farm animals bred for food and docility.
sheep
Koalas are famous for their reduced brains.
NM
Sloths?
We saw that one coming! 
My dog has to be at the bottom of the intelligence pile. Cute he is but he’s basically a big sack of stupid. Unless it is about food. Then he wises up fast enough 
I nominate the now-extinct Coryphodon, based on its brain/body size ratio. They had “a brain weighing just 3.2 oz and a body weight of around 1,100 lb.” They look fairly hippopotamatic in the pictures there.
Tangentially, I don’t think humans are even close to being the dumbest mammal. In fact, we’re probably too smart for our own good. But we seem to have a strange predilection for exactly the things that are worst for us. More and more food, a fondness for drugs like nicotine/caffeine/opiates, soap operas, more cars and televisions than the number of people living in our home, and an unquenchable desire to consume exponentially more information without benefit or reason (except temporary pleasure). You don’t see squirrels or rabbits or cows doing this kind of stupid shit, that’s for sure.
No no, they’re just magnificently efficient. Seems pretty smart to me! 
I don’t have a wide experience with mammals. However, every hamster I’ve had has been pretty dim. We could teach them, somewhat, that certain foods are tasty (our hamsters universally loved raisins, for what it’s worth) but as a whole hamsters just don’t learn much, and they don’t learn quickly. And it’s not just their size, or that they’re rodents. Rats aren’t that much bigger, but rats are noted for being actually fairly bright. Hamsters will repeat behaviors that hurt them every time. Rats will try to figure out a new way of doing things. This is probably why we don’t have hordes of wild/feral hamsters that need to be exterminated in our homes.
Now if you want to ask about stupid birds, I’d nominate the domestic turkey. They are damn near too stupid to feed themselves.
I was going to go on about stupid birds, but… um… they aren’t mammals.
As for mammals, i would say hamsters. They are untrainable. That, in my mind, defines non-intelligent. I am certain that there are less intelligent creatures out there but I have not yet encountered them. Fluffy Bumpkins (hey my wife named her) couldn’t even complete a maze with hamster treats at the end.
So hamsters are just dumb.
There… I’ve said it!
Now, I must huddle here and wait from a knock at the door from the ASPCA.
The horror… the horror.
I don’t think you’ll get a definitive answer on this. There really is no standard metric for saying this animal is smarter than that one.
Absolute brain size and brain to body ratios can somewhat be a guide, but there are animals with what we consider advanced behaviours with small absolute or relative brain sizes e.g. ants, crows, octopuses.
I never got the whole brain size/body size ratio as gauge of intelligence thing. Are fat people dumber than thin people? Are amputees smarter?
Well, it’s not supposed to be for comparing individuals, it’s for comparing different species. And the reason it’s thought to be an indicator, is that certain tasks that a brain has to do, will scale with organism size e.g. the bigger you are the more nerves you will generally have.
Having a large brain compared to your body implies there is enough brain capacity for all the “basic” functions (like handling all that nervous input), plus some extra, which may have evolved for more “advanced” behaviours.
But as I said, there are plenty of counter-examples, if we were to take this as an absolute rule. And it could be misleading comparing, say, reptiles to mammals, because some of the mammalian brain may be tied up with functions like temperature regulation.
Whoosh?
IME ferrets are pretty damned dumb, outside of a nearly supernatural ability to get into stuff their owners wish to keep them out of.
The North American Celebrity Worshipper.
I have heard that manatees score poorly on most standardized tests.
A huge muscle, say the size of a house, does not necessarily need more processing power to command it than does a tiny one. Note the huge amount of human brain devoted to controlling the muscles of the hands compared to say the thigh muscles. It is a commonly used metric but one that bespeaks to the intellectual laziness of the scientists who used it, as otherwise defining “intelligence” cross species is difficult, other that by defining it in a anthrocentric manner.
Anyway, I vote hedgehog. Not many convolutions there. It is a very primitive mammal that has stuck with the same basic brain form from the days they likely scurried under dinosaurs. They’ve changed virtually naught at all in 70 million years. They seem to have found intelligence and evolved brains to be a new fanagled thing they don’t need.
As the above implies, the entire issue of defining “intelligence” is heavily colored by human bias, blind spots, assumptions, insecurities, wishful thinking, and poor observation.