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Abstract

Foraging animals must often be sensitive to the dual risks of predation and energy shortfall, and should devalue risk of predation as risk of starvation increases. This study examines whether the probability of colony-level energy shortfall influences the predation risks taken by individual foraging bumble bees (Bombus occidentalis) in confined colonies as they collected sugar water from artificial flowers. Before each trial, colony energy stores were manipulated by enhancing or removing the contents of the colony's honey pots. Feeding bees were significantly more likely to flee from an artificial predator model (a black styrofoam ball moved overhead) when their colony's energy stores were enhanced, relative to when their colony's energy stores were depleted. Despite their defensive stings and aposematic coloration, bumble bees are more likely to accept “risky” foraging situations when the energy needs of their colony are increased.