Don't only humans understand the concept of death?
We have direct evidence that other animals do understand the
concept of death. For example, when elephants pass the skeletal
remains of old friends during their migration, they stop and seem
to mourn. We can not be certain what these elephants are
thinking, due to the fact that we do not yet know how to
communicate with them.
However, we can communicate with animals such as chimpanzees through sign language. There was a case where a chimpanzee infant died during surgery, and it was the duty of the trainer to tell the chimp's mother, in sign language, that her baby had died. According to the trainer, it was clear that the chimpanzee mother understood, and that she reacted in the same manner that any human mother would.
Follow up questions:
Where in the animal kingdom does consciousness begin?
Don't only human beings have a soul?
How can some animal rights activists believe that other animals are our equals?