Dominance Relationship and Mating Behavior of Domestic Cocks: A Model to Study Mate-Guarding and Sperm Competition in Birds

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Abstract
A random-bred strain of domestic chickens (Gallus gallus) in single-male and two-male mating groups was used as a model to study strategies of mate guarding and sperm competition. The experiment was designed to examine influences of (a) the presence of a rival male, (b) dominance status of the males in the two-male groups. and (c) the time of day on the frequencies of male courtship and copulations. In the absence of rivalry, male chickens copulated infrequently in the morning and increased the frequency of copulations throughout the day until a maximum was reached in late afternoon. In the two-male groups the domanant males copulated more frequently than the subordinate males. They also competed by altering their diurnal pattern of mounting attempts and increasing their rate of successful copulation per attempt. The subordinate males made frequent attempts to mount the females regardless of whether they were receptive. However, their success rate was low because of interference by the dominant males, especially at that time of the day when a successful insemination would likely fertilize eggs. The experiment showed that not only the relative numbers of copulations by different males, but also the timing and success of copulations by different males may influence the probability of paternity. Furthermore, the interplay of proximate mechanisms and evolutionary factors contributed to variations in mating strategies.