Territorial behaviour and population dynamics in red grouse Lagopus lagopus scoticus. I. Population experiments
Article first published online: 10 NOV 2003
Journal of Animal Ecology
Volume 72, Issue 6, pages 1073–1082, November 2003
How to Cite
Mougeot, F., Redpath, S. M., Moss, R., Matthiopoulos, J. and Hudson, P. J. (2003), Territorial behaviour and population dynamics in red grouse Lagopus lagopus scoticus. I. Population experiments. Journal of Animal Ecology, 72: 1073–1082. doi: 10.1046/j.1365-2656.2003.00781.x
- Issue published online: 10 NOV 2003
- Article first published online: 10 NOV 2003
- Received 12 February 2003; accepted 30 June 2003
- territorial behaviour;
- unstable population dynamics
- 1According to the ‘territorial behaviour’ hypothesis, population cycles of red grouse are caused by delayed density-dependent changes in the aggressiveness of territorial cocks. We report here on a replicated population experiment testing assumptions of this hypothesis.
- 2We used testosterone implants to increase aggressiveness of cocks for 3 months during autumn, when recruitment and territory establishment take place. On two moors located in northern England, and on two 1-km2 areas within each moor, we implanted adult cocks with testosterone on an experimental area and with sham implants on a control area.
- 3During the first autumn, the testosterone treatment prevented recruitment of young cocks into the territorial populations. This reduced breeding density and altered the age ratio among territorial cocks, and possibly levels of kinship. If so, the ‘kinship’ hypothesis predicted that density and recruitment should continue to differ between testosterone-treated and control areas.
- 4Grouse density remained significantly lower on the experimental than on the control areas for two consecutive breeding seasons. This confirmed a strong spatial structuring within grouse populations, which prevented immigration from neighbouring higher-density areas. In the second autumn, testosterone was not implanted but the recruitment rate remained significantly lower and cock density continued to decline more on the experimental than on the control areas.
- 5The results suggest that cocks continued to be aggressive and to maintain large territories for at least a year after aggressiveness was increased experimentally, and therefore that autumn aggressiveness is influenced by previous territorial contests.
- 6The experiment validates key assumptions of the ‘territorial behaviour’ hypothesis for red grouse cycles. Population models in a subsequent paper demonstrate how changes in aggressiveness can cause population cycles.