Predation, aggression, and activation levels in food-deprived sunfish (Lepomis macrochirus and L. gibbosus): Motivational interactions.

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Abstract
The effects of food deprivation on several behavioral categories in 2 spp. of sunfish were investigated. Predatory behavior and general activity were observed under 5 levels of deprivation. For both species, predation measures increased in a similar negatively accelerating manner with increasing deprivation, while activity changed in a more complex fashion. The effects of deprivation on activity in a novel environment were examined. Deprivation effects were masked by the response to the new setting. Measures of aggression toward intruders of each species were recorded from resident fish of both species under 3 levels of food deprivation. Both species were more aggressive toward conspecifics, and bluegills were more aggressive overall. Aggression was significantly influenced by food deprivation, with the effects dependent on the species making up the pair. Theories of motivational summation, generalized drive, and activity-mediated aggression do not explain the differential effects of hunger on the 3 behavioral categories observed. A dynamic boundary-state model of behavior control predicts the motivational interactions observed between distinct behavioral control systems.