  Zooplankton in a quiescent environment can detect predators by hydrodynamic
sensing, triggering powerful escape responses. Since turbulent strain tends to
mask the hydrodynamic signal, the organisms should avoid such regions, but it
is not known how they accomplish this. We found a simple, robust, and highly
efficient strategy, that relies on measuring the sign of gradients of squared
strain. Plankton following this strategy show very strong spatial clustering,
and align against the local flow velocity, facilitating mate finding and
feeding. The strategy has the potential to reconcile competing fitness
pressures.
