Isn't it the case that prey animals such as hares, rabbits, deer, antelope, horses etc etc have evolved to enable themselves to run the same whether they have been feeding or not ? If this wasn't the case then I think the predators in the savanna would soon switch on to this fact wait until mid afternoon when the animals were well fed and have an easy time of picking them off ... I would think if that was the case lots of prey animals would be extinct and the predators would starve to death .......