Have species evolved to drop limbs on one side, perhaps strengthening them on the other, so that they could more perfectly hold each other? She smiled. She remembered a lesson at a youth class at the local zoo she had taken that her Mom had signed her up for. There are some creatures, during the night or whenever they are likely to be prey, who line up on a perch three or more, and the ones on the outside maintain more wakefulness than the ones buffeted by them for protection in the middle.