I've always wondered that!!!?? I read a study once, that animals can experience a profound feeling of sadness when their play/hunt/sex partner dies. So can they commit suicide?
The answer lies in the difference among human and animals about awareness of life, "conscious self awareness" is found only in human beings, while an "instinct awareness of life" is found in animals. Any change in preordained instinct is a result of conscious departure from genetic inclination, animals are not capable of that.