I wouldn't have a clue as to why. I noticed that behavior in other animals as well.Have you ever watched a mass of starlings in flight. They don't seem to be following each other as much as instinct kicking in. I mean I have watched other them for long periods of time. ( TV broke... Medical marijuana kicking in! ) They all turn, climb, dive in unison. Which means to means to me, they're not really following each other. Which fly's in the face of a Cornell University 20 year, 2.3 billion dollar, tax payer granted study of this sort of animal behavior. There conclusion was praised and accepted by the scientific community. The official study is was named Monkey see, Monkey do... True story...