The field of behavioral ecology began in the mid-1970s with studies of foraging behavior. The majority of these studies examined how solitary foraging could be explained by optimal foraging theory. However, many animals forage in social groups, from aggregations to coordinated groups. Evolutionary pressures on social foraging differ from those on solitary foraging.
Predictions about the evolution of solitary foraging are based on the marginal value theorem, an economic model that assumes that animals should behave in ways that optimize their nutritional gain relative to the costs of obtaining food. In 1973, Ward and Zahavi were among the first to incorporate social behavior explicitly in foraging models with the 'information center hypothesis'. This suggested that individuals might obtain information from other group members about the location of food. Social foraging theory was later developed using game theory and the concept of evolutionarily stable strategies to predict how animals should behave within a social context. From this theoretical perspective, predictions have been made about when social foraging should be favored over solitary foraging, how individuals within a social group should search for food, when social groups should abandon patches, and the role that inter-individual variability and learning may play in social foraging.
As yet, few empirical studies of social foraging have tested these theoretical predictions. Nevertheless, considerable empirical work has been aimed at understanding the impact of social behavior on foraging. The 'information center hypothesis' may have played a role in the evolution of communal roosting in birds. Social learning has been demonstrated to affect foraging performance in fish and other vertebrates (e.g., chimpanzees). Individual differences are important in socially foraging groups; for example, in house sparrows, Passer domesticus, social dominants scrounge more food from subordinates under conditions of nutritional stress. Probably the largest body of work on social foraging has been conducted in the social insects including ants and social bees. Ants use a variety of behaviors, including laying chemical trails, interactions, direct recruitment, and carrying nestmates, to recruit and collect food items. Honeybees use the famous waggle dance, discovered by Karl von Frisch, to communicate the location (both direction and distance) of food sources to their social nestmates. While these communication mechanisms are often assumed to result in the optimum efficiency of social foraging behavior, we know of no studies under natural conditions that have demonstrated such optimality.
Cooperative hunting, where individuals in a social group work together to acquire prey, occurs in many vertebrate (e.g., hawks and lions) and invertebrate species (e.g., ants and spiders). Cooperative hunting may fundamentally alter food chains and food webs, if predators rise to a higher trophic level due to the ability to capture larger prey when acting as cooperative groups, or if the connectivity of a food web increases when predators can incorporate a more diverse range of items in their diet.
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