Components of predation defense behavior in chickens: evidence for endogenous rhythmicity.

The manifestation of diurnal periodicity and the extent of its control by the photoperiod was assessed in three predation defense reactions which constitute either components or outcomes of a predator-prey interaction sequence. Two-hundred White Leghorn chicks were reared from hatching for one week in either 24L or 12L and then tested at one of two clock hours previously demonstrated to define peak and trough response for one of the components. Putative evidence was found for an endogenous source of the periodicity manifested in all reactions. Maintenance schedule did not entrain the periodicity, but simple room entry and handling elicited anti-predator reactions, the extent of which varied as a function of clock hour. A general model of predation defense behavior was proposed.

Periodicity of death feigning by domestic fowl in response to simulated predation.

The presence and extent of periodicity in the manifestation of death feigning duration was assessed in 137 week-old White Leghorn chicks. Chicks were reared on an LD 12:12 regimen with light onset at 0800 hr. Each was tested only once at one of 13 clock hours spanning a 24 hr period. Death feigning duration varied significantly with clock hour of induction, being longest from 1300-1400 hr and briefest from 0600-1100 hr. Variability was also cyclic but was distributed bimodally, being greatest in the latter half of each L and D phase. There was no significant influence of management hour on death feigning duration. The adaptive significance of the periodicity for predator-prey interactions was discussed, as were methodological implications.