Induced Swarming in the Predatory Copepod Heterocope septentrionalis

Adults of the predatory calanoid copepod Heterocope septentrionalis are not randomly distributed in natural habitats: they aggregate above areas of pale substrate. When panels of yellow or white plastic were placed in ponds near Churchill, Manitoba, swarms with up to 300× the ambient density formed. These aggregations were most dense when light intensity was high and wind strengh low. The attraction to pale substrates was not transient; adults showed the response through their life-span. From an adaptive standpoint, the behavior may enhance the frequency of mating encounters. The occurrence of swarming provides a simple way of manipulating predator densities in these habitats.