Here in Maine, many (not all), will eat deer liver and heart if they like cow liver and heart. Heart from Moose and black bear are good too, but liver is different. Bear liver is ok but can have a high concentration of vitamin A and can make you temporarily sick from Vitamin A toxicity. That's the reason you should not eat Polar Bear liver (although other than a few Inuit friends, I don't think that is very likely). Black bears are more omnivores so the concentration of Vitamin A should be a lot less than Polar Bear and is ok in moderation and spread out over a period of time...personally I do not eat it, but love bear heart. I will not eat Moose liver due to cadmiun (a heavy metal) concentration. It will not likely kill you but will make you wish you were dead if you overdose and takes a long time to get rid of it in the body. Cadmium comes from Copper and Nickel industries and the burning of fossil fuels in northern US and parts of Canada. Maine, much of Canada and Scandinavian countries recommend against eating Moose liver.
Bill