um...well theres several possibilities. the giraffe has uniquely evolved to be able to reach its food source at the tops of trees, which, through their own genetic evolution, have become taller over the ages. pandas and moose and giraffes are all herbivores, while grizzlies and tigers are omnivorous, having a much more scrutinizing digestive system that will allow them to process various types of intake. pandas have evolved a unique claw on their forepaws that allows them to dig out the center meat of bamboo stalks and other closed-capsule plants.
each animal has its own unique evolutionary quirks involving digestion and eating, so which is it. give it up already :p
EDIT:
you also broke the game code by not labeling which was decaf/regular. thats the point. you have to figure out why the different one is different. not which AND why.