While there's still some debate as to the extent that animal emotions mirror our own, the feeling of mourning over the loss of a loved one can be readily sensed in creatures big and small.
"There is no doubt that many animals experience rich and deep emotions," writes animal behaviorist Dr. Mark Bekoff in Psychology Today. "It's not a matter of if emotions have evolved in animals but why they have evolved as they have. We must never forget that our emotions are the gifts of our ancestors, our animal kin. We have feelings and so do other animals. Among the different emotions that animals display clearly and unambiguously is grief."