I have recently discovered that when gerbils get old, they are killed by their offspring. 

Recently, I have seen that happen in two cages of our pets.  In one cage, two sons ganged up on their father.  I was there when it happened and quickly rescued the father from his dire fate.  He now survives in solitary existence, which is something gerbils generally do not prefer.  They are sociable creatures, loving the companionship of each other, sleeping in mounds, piled upon each other.   Should I have left him to die at the hands of his children as perhaps nature intended, or should he now be forced to live a lonely life and die quietly by himself after months of dreadful solitude?  Perhaps I should have had, or should have, the courage to quickly end his days.

Most recently, in another cage, the mother was viciously attacked by one of her two daughters, with results more graphic than I will go into here.  Both mother and daughter had to be destroyed. 

I assume that there must be other species of animals, where, in the absence of natural predators, the old and weak are destroyed by others of its own community and family.

As humans, we consider creatures to be more advanced based on the degree of care they offer to their sick, injured, and elderly counterparts, with the acknowledgement of higher emotions like love and empathy, and perhaps as recognition of the value of life.

When our pets and other animals in our lives are ill and suffering, we relieve that suffering and pain, calling it humane. I, myself, have taken a sick dog to the vet for her last moments of life when her condition in life became unbearable.  I believe it was the humane thing to do. 

Yet, when, as humans, our human family members are ill, suffering, and waiting for and wanting death, which we all seem to inevitably witness, we can not completely eliminate their suffering.  We and they must wait for death, and, sometimes, it can be a long, long wait.  I am most certainly not condoning euthanasia, but merely wondering, as most everyone before me has wondered, why we almost appear to be more humane to the other animals in our life than to those we love the most. 

At what point did those gerbils decide that the lives of those with whom they snuggled and cuddled for years and since birth are not worth living?  Are they trying to prevent the future discomfort and deterioration that accompanies aging?  Or were they merely acting with instinct, that when a gerbil becomes too weak to defend itself, it is destroyed by the stronger?  Personally, I suspect it is a combination of the two, the instinctive reaction to eliminate the weak, with an outcome that results in the former.

From the perspective of both a child and a parent, all I can say is that I am glad I am not a gerbil.