I’ve seen them described that way, based on their diet being almost entirely meat. But what I’m wondering is if that might possibly be simply because their habitat (which they are adapted for) happens to have not much in the way of plant matter. But is there anything in their teeth or digestive systems which differs dramatically from that of other bears? Suppose you had a polar bear in a zoo, could you feed it a diet similar to a grizzly bear, or does it need meet only?
According tothis they are still omnivores. Makes sense in an environment where food is scarce.
I know a personal anecdote is weak sauce in GQ, but I’ve seen polar bears fed with fruits and vegetables in a zoo.
Since they only split from Brown Bears, which are largely herbivorous, about 150,000 years ago, I doubt whether they could have diverged very much in physiology. They are certainly not exclusively carnivorous, since they will include berries, roots, seaweed, and grass in the diet. With global warming making their main food of seals less available, in some places they are including more vegetable foods in the diet.
It should be clarified what “obligate carnivore” means. This doesn’t refer to what proportion of the diet is meat, but that meat must be included in the diet to avoid nutritional deficiency. Cats are obligate carnivores since they need to get the amino acid taurine, found in meat, from their diets. Most other animals are not.
(It might be noted that humans in a sense are obligate carnivores, in that we need vitamin B12, which comes almost exclusively from animal sources. But obligate carnivore is not usually used in that way, since we can get it from milk, cheese, eggs, etc.)
B12 is also found in fungi. You’d probably have a hard time meeting all of your protein needs from fungi, but if it’s just a micronutrient you’re worrying about, it’s much easier.
On the other end of the spectrum, giant pandas, which are largely thought to be almost exclusively vegetarian, are capable of eating meat, their digestive systems are no different than any other bear, they simply choose not to (apparently because they’ve lost the ability to taste meat, or at least it doesn’t taste appetizing to them). Pandas have been occasionally filmed eating carrion, and will scavenge if presented the opportunity, but I’d imagine their hunting instinct is poor if not nonexistant.
Polar Bears, Brown Bears and Grizzlies* are all very close and they still interbreed with mostly fertile offspring.
Latest genome comparisons pushed the split back to 400,000 years ago, but that there has been interbreeding throughout that time.
- Grizzlies are actually just a brown bear subspecies.
I do find it amusing that the mammal whose natural diet is most nearly 100% meat, and the mammal whose diet is most nearly 100% plants, are both bears.
And there are a lot of ways that giant pandas are too stupid to figure out that whole “being alive” thing. It’s amazing that they haven’t already gone extinct even without human pressure.
Their survival strategy of “Hey, we are cute! Those weird apes will take care of us!” is very much a last roll of the dice. 
They wouldn’t have needed that last roll if those naked apes hadn’t destroyed their habittat in the first place.
And just because animals raised in a zoo couldn’t figure out sex doesn’t mean that they can’t figure it out in the wild.
Is that really the case though? About 100% of my meals would be vegan unfriendly in some way, but vegans exist and as far as I can tell are mostly pretty healthy, they’re not a fringe group or universally frail.
I still think George Carlin (the only comedian we ever needed) has this figured out.
Vegans are prone to vitamin B12 deficiency unless they take steps to avoid it with B12 fortified food or supplements.
I’m going to have to ask for a cite on that one.
From what I’ve learned about it, fungi do not produce B12, only bacteria do. If the mushrooms have been fermented, they may have some from the bacteria that do the fermenting.[sup]1[/sup] Or if they aren’t thoroughly washed, there may be a bit left from the soil bacteria on them, although it’s not certain that that is a form of B12 that’s bioavailable to humans.
[sup]1[/sup] Tempeh, which is fermented, has some B12, but it’s not a lot. You’d have to eat several servings to get your RDA.
OK, put it this way. Human babies are pretty helpless, right? All they’re good at is sucking and pooping.
Panda babies aren’t even good at pooping.
Kittens and puppies also need assistance in defecating, when they’re young enough. I wouldn’t be surprised if there are other mammals who do also.
Whatever you do, if someone offers you the liver, just say no.
Nothing good has ever come from eating polar bear liver, even in the most dire of circumstances.
It’s a way to keep the nest clean.
Dunno. I think people with chronic dietary Vitamin A deficiency are treated with occasional large doses, not lots of small doses. And systemic retinoids are sometimes used for skin cancer and other dermal conditions (along with birth-control pills if appropriate, because of teratogenic effects).