Territorial status and survival in a low density grouse population: preliminary observations and experiments.

Abstract

1. The role of territorial status and survival of female grouse was examined through radio-tracking and density-manipulation experiments. Sex ratios favoured males, and so monitoring and experiments concentrated on females as the sex which limited breeding density. No significant difference was found between the survival of territorial and non-territorial females, unlike earlier studies in north-east Scotland (Watson 1985). Territorial and non-territorial females were both more likely to die from predation than in previous studies.
2. In a low-density population in Speyside, the majority of heather-dominant moorland was not used by grouse in spring. Approximately 24% of grouse introduced into this low-density population (trap-and-transfer experiment) subsequently bred. The experiment was replicated a total of 5 times at different densities, and, on each occasion, introduced grouse subsequently bred. Removal of female grouse in spring recorded no non-territorial females, and numbers of territorial females were greater in spring than autumn.
3. On the main study area, significantly more corpses were the result of predation than in earlier studies, and this was associated with an apparently higher predator population, despite a lower grouse population. Muscle weights of female and male grouse alike were no different from those of grouse dying from accidents, suggesting that predators did not select weaker individuals.