Selective habituation of defensive behavior: Evidence for predator-prey synchrony

The selective nocturnal persistence of death feigning, an antipredator behavior, was assessed in four studies involving single daily trials. In Experiments 1 and 2, White Leghorn chicks exhibited a progressive decline in death feigning durations in both the light and the dark phases of their photoperiods over 8 days, but resistance to habituation was greater at night. When nocturnal death feigning was induced to a habituation criterion (Experiment 3), it was extremely persistent and was not completely abolished in some chicks, even after 25 consecutive test days. Because nocturnal response durations of chicks tested cross-sectionally increased over the same developmental period (Experiment 4), a shifting developmental baseline was excluded as the basis for the declining response durations observed in the first three studies. The differential plasticity of death feigning at two times of day is consistent with the argument that predatorprey synchrony confers a selective advantage, and suggests an additional biological constraint on learning.