  We obtain a Fokker-Planck equation describing experimental data on the
collective motion of locusts. The noise is of internal origin and due to the
discrete character and finite number of constituents of the swarm. The
stationary probability distribution shows a rich phenomenology including
non-monotonic behavior of several order/disorder transition indicators in noise
intensity. This complex behavior arises naturally as a result of the randomness
in the system. Its counterintuitive character challenges standard
interpretations of noise induced transitions and calls for an extension of this
theory in order to capture the behavior of certain classes of biologically
motivated models. Our results suggest that the collective switches of the
group's direction of motion might be due to a random ergodic effect and, as
such, they are inherent to group formation.
