I think you missed the point of the study. In experiments involving human babies and rhesus monkeys, the subjects were shown a number of objects they would be intersted in (toys for babies, apple slices for the monkeys.) In each case, the subject would stare longer at the objects if one was taken away, than if the number had stayed the same. They were able to tell that the number had changed. Not all animals exhibit this sort of "counting" skills.
I think you missed the point of the study. In experiments involving human babies and rhesus monkeys, the subjects were shown a number of objects they would be intersted in (toys for babies, apple slices for the monkeys.) In each case, the subject would stare longer at the objects if one was taken away, than if the number had stayed the same. They were able to tell that the number had changed. Not all animals exhibit this sort of "counting" skills.