In the animal kingdom animals also expand to fill voids. You can see bulls expanding to include as many females in their domains as possible. They strut and prance and mark their turf and then defend it. They will sire as many females as they can. There is no end to their ascent until they are defeated by another bull. Before they are dethroned, it is as if they feel powerful and omnipotent. It is only defeat that puts a dent in their self-importance.
This is why large animals as pets cause a problem. When little, their world is their oyster, and they play and fool around. They submit out of fear, but one day they will test their boundaries with the potential to cause serious damage. Tigers and chimpanzee stories testify to this. If they were loved, taken care of, the universe seems a terrific place until they test the mouths that feed them and ….....!
One hippopotamus, dethroned by a competitor, went off as if to sulk alone. He had a lot think about. The universe used to be his. What happened?