Effects of body size and sociality on the anti-predator behaviour of foraging bees


M. A. Rodríguez-Gironés, Estación Experimental de Zonas Áridas, CSIC, Carretera de Sacramento s/n, ES-04120 La Cañada de San Urbano, Almeria, Spain. E-mail: rgirones@eeza.csic.es


Pollinators, like most other animals, often face a tradeoff between increasing food uptake and minimising predation. An earlier model suggests that social bees should be more likely than solitary bees to adopt riskier foraging strategies in order to increase food uptake. In this paper, we extend this model by studying the effect of body size, in addition to sociality, on the predation–intake rate tradeoff. When, following standard practice, we express the foraging strategies in terms of mortality probability and net food uptake, we find that body size should have no effect on the foraging strategies of solitary bees. Social bees, on the other hand, should change their foraging preferences according to their size. Small social bees should tend to maximise food uptake, and large social bees to minimise mortality rate. Mortality, however, is the product of two terms: the probability of suffering an attack and the probability of succumbing to it. Noting that larger bees are less susceptible to succumb to a predation attempt than smaller bees, model predictions change when foraging strategies are expressed in terms of exposure to predators. Following this second approach, exposure to predators should increase monotonically with body size in solitary bees. In social bees it should reach a minimum for medium-sized bees. We conclude that both bee body size and sociality should be considered when studying the effect of predators on resource use.