I think, about the whole food bar etc... Killing prey, could give everyone of your group (The pack/pride that is hunting it) expierience. This could be used in a Stamina and/or Life bar system, to make your animal last longer in a hunt. But maybe that should be left out, and just counted by points. Then you could brag about how many Elephants your pack got down, and show proof from ingame :3
About the Life bar and Stamina bar
If prey hits you, you get life points taken off. This can be healed by either resting(like IT) or eating the prey afterwards. And a stamina bar, that gets smaller with each attack you do at the prey. Therefor you would -need- to have a pack to take down bigger prey. Smaller animals, such as bunnys and stuff could still be nommed without help.
Also, I think animals should drop an item, such as in food items. Since I think it will be hard to code in prey carring, you could simply carry a food item, such as a Leg or something, back to your place and feed left behind cubs and family members.
To the realistic part, with food and water:
I don't think it should be implemented, to survive only with food and water source... buuuuut, why not make these two bars, and make them blend in or out if someone wishes to have survival. There wouldn't be consequences, if it ran out (since, what would you do if that happend?) but it would give the whole game a challenge. Rp and survival. Perhaps a survival timer, that saves how many days you "survived" without running out of food/water.
And we should make sure to make it realistic. I think, Lions only hunt once every one or two days? Correct me if I'm wrong, I have no idea X3
And I think Kovu said he would maybe put in hunting, earlier in this post o_o
(long post is long)
