In a TV show last night, a video was shown of about 20 turkeys, continuously walking and following each other around a circle of radius 8 feet.
There was a dead cat in the middle.
I did not buy the theory that the turkeys were hypnotized.
My explanation is that the turkeys were engaged in Mutual Pursuit. That they liked to follow each other.
The turkeys perception of the danger of the dead cat prevented the collapse of the mutual pursuit curve.
(The turkeys did not recognize that the dead cat was no longer dangerous.)
How the circle began is not clear. :-)

- Brian