It has nothing to do with love or loneliness. Those are human conditions. The animal is an animal, and not a human.
I beg to differ. Have you never seen a video of a dog that thought it had lost its owner? Only to have him reappear a year later.
Can you honestly say that the animal has not experienced love and loneliness?
I disagree. I have watched many animal videos over the years, and I do believe that some higher animals are certainly capable of experiencing loneliness, depression, and grief.
Please see this part of the video linked at 6:21. Flint was an adolescent chimp that was overly attached to his mother, Flo. She was older when she had him, and she spoiled him. He couldn’t move on naturally like his brothers and sister. His attachment was not healthy...just like some humans get. And when she passed, he was not able to get over his grief.
http://www.youtube.com/watch?v=OqRTTUAGXrk&t=6m21s
I can provide other examples of this same sort of thing. I’ve seen stories and videos of it regarding dogs. Certainly primates. Elephants.
Please have a look at John Gluck’s book