Feeding and Avoiding Predation Hazard: the Behavioral Response of the Prey

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Abstract
A forager may respond to the hazard of predation by (1) ignoring the hazard and eating maximally at all levels of food (risk‐reckless); (2) avoiding the hazard and minimizing eating (risk‐avoiding); (3) reducing feeding by the same amount at each level of food, making greater reductions as hazard increases (risk‐adjusting); (4) reducing feeding at low levels of food, while accepting a greater hazard when food levels are high (risk‐balancing). We experimentally distinguished these four nominal responses using 9 three‐spined sticklebacks, Gasterosteus aculeatus in a 3 times 4 factorial, repeated measures design. The fish were tested in an aquarium containing a refuge inaccessible to predatory trout, Salmo trutta, in 12 combinations of food (low, medium, high) and predation hazard (predator density = 0, 1, 2, 3). With predators, sticklebacks ate less and used the refuge more. Amount eaten, but not time spent out of the refuge, was positively correlated with food, even in the absence of predators. Since sticklebacks as a group appeared to depress feeding by equal amounts at all levels of food, they employed a risk‐adjusting response. However, individuals varied in their response to hazard.