I own all three versions of World of Zoo (Wii, PC, and DS) and while I have spent more time on the Wii version than any other, I have noticed some baffling differences. The Wii version contains eleven types of animal to play with - crocodiles, big cats, bears, giraffes, monkeys, antelopes, elephants, horses, pandas, koalas, and penguins. The PC version is functionally similar but features only half the roster - big cats, giraffes, monkeys, horses, pandas, and koalas.
I have honestly not played much of the DS version at all (I will eventually). It is different than the Wii and PC versions, featuring pixellated graphics and different UI. On top of the full Wii roster. it also features an exclusive twelfth animal - canids! I am disappointed these were not in the Wii version and confused as to why. As a dog- and wolf-obsessed kid, I would have loved playing with them! (I didn't get the DS version until I was older - I think it was pretty cheap on GameStop's used games rack.)