All photographs by R. A. Scrosati
Predators may have nonconsumptive effects (NCEs) on prey populations mediated by chemical cues detected by prey. We experimentally investigated dogwhelk (Nucella lapillus) NCEs on intertidal barnacle (Semibalanus balanoides) recruit density in Nova Scotia, Canada. Under a moderate abundance of coastal phytoplankton (food for barnacle larvae and recruits), barnacle recruitment was moderate and the nearby presence of dogwhelks limited barnacle recruit density at the end of the recruitment season. Under a high phytoplankton abundance, barnacle recruitment was high and neutralized dogwhelk NCEs on barnacle recruit density, likely through the chemical attraction that recruits exert on larvae seeking settlement.
These photographs illustrate the article “Predator nonconsumptive effects on prey recruitment weaken with recruit density” by Julius A. Ellrich, Ricardo A. Scrosati, and Markus Molis, published in Ecology 96(3):611–616. http://dx.doi.org/10.1890/14-1856.1