Sometimes when life is hard you need a buddy. Fish are well known for their propensity to form groups (i.e. schools or shoals), and the formation of these groups can provide all sorts of anti-predator benefits including predator confusion, group vigilance (e.g. alarm calling or predator mobbing), and predator dilution. Of course, the benefits of group formation may or may not be outweighed by the negative effects of group living such as the aggregation of predators or increased resource competition among prey in areas of high density. Therefore group formation can lead to benefits and consequences for prey, but also can change how the overall foraging success of predators. The importance of prey density in modifying predator foraging behavior has been established for some time in Ecology for all sorts of processes including the stability of predator prey dynamics, the spatial distribution of predators, and the strength of species interactions in diverse food webs. However, the effects of prey density on predator foraging behavior can vary substantially with both predator density (e.g. due to phenomena such as intraguild predation, interference competition, or cooperative hunting) and the presence of multiple alternative prey species (e.g. due to competition within the prey community or aggregation of predators to areas of high prey density). Our empirical understanding of how different components of predator foraging behavior shift with predator density and the presence of multiple prey species remain limited.
We develop and apply an explicit statistical framework that combines predator functional response curves and short-term aggregative response of predators by estimating shifts in attack rate, handling time, and effective preda- tor density as alternative mechanistic models explaining variation in mortality rates of prey. For each experiment, we take both a ‘predator-centric’ (examining feeding rate of a single predator, as a function of prey density) and ‘prey-centric’ approach (examining per capita prey mortal- ity rate, as a function of prey density).
Title: Predator and Competitor Dependent Benefits of Group Formation in a Coral Reef Fish
Authors: Adrian C. Stier, Shane W. Geange, Benjamin M. Bolker
Stier, A. C., S. W. Geange, and B. M. Bolker. 2012. Predator density and competition modify the benefits of group formation in a shoaling reef fish. Oikos:online early.