Ardea
Official journal of the Netherlands Ornithologists' Union

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Moss R. & Watson A. (1980) Inherent changes in the aggressive behaviour of a fluctuating Red Grouse, Lagopus lagopus scoticus, population. ARDEA 68 (1-4): 113-119
Field work suggests that the best general explanation for cyclic changes in Red Grouse densities is, changes in spacing behaviour at different phases of the population cycle. Two specific hypotheses, the 'maternal nutrition' and the 'genetic' hypotheses, both predict that aggression should be inherited. We tested this prediction. Each year a sample of eggs was taken from a fluctuating population of Red Grouse. These eggs were hatched in captivity, and the chicks from them reared in standard conditions. When the cock chicks were full grown we measured their dominance i.e. their rank in a linear peck order. The dominance ranks of our yearly samples decreased while the density of the wild population increased, reached a minimum one year after population densities were at their peak, and increased as the population declined. Several specific predictions of the 'maternal nutrition' hypothesis were falsified. Other work in the aviary showed that dominance rank had an inherent component. Our data could be mimicked by a simple mathematical model which assumed two types, of high and low aggression. As a result of this work we put forward the hypothesis that, as Red Grouse populations increase in density, unaggressive genotypes proliferate until peak densities are reached, when selection for aggressive genotypes begins and causes a decline in numbers.


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