Behaviour and conservation: habitat, population, territorial and social dynamics of black grouse (Tetrao tetrix) at the arenas during a long term study in the Hautes-Fagnes of Belgium

In the wild, an animal has to find food and shelter, avoid predators, select a partner to copulate. All these necessities are modulated by the habitats scale and structure and by the population density. Black grouse is an endangered species in Western and Central Europe. Social units are scattered, often small with few individuals. The Belgian Hautes-Fagnes Nature Reserve is probably the most werstern sanctuary of the species on the continent. Over years, the original landscape convenient for Black grouse has been reduced to one third (5,000 ha most under protection now). The Black grouse numbers have fluctuated since the mid-sixties between 198 (1971) and 18 (2000) cocks. Censuses have been organized annually on 30 arenas. Some have been under daily control in spring for years. Three types of arenas structures can be seen: on natural habitats (bogs, small patches of heather, mowed moorland), arenas look like tight clusters of small territories where competition is high between the more central males who rarely are allowed to develop their courting behaviour; arenas in line where territories equivalent in space and situation follow each other on the grassy strip of a one kilometer long firebreak; important differences appear in courting and copulation success between apparently equal landowners; extended arenas with larger territories on artificial meadows where even the most central males have sufficient space to court with success. On such an arena, a long term study from 1971 to 1979 allowed to record the courting skill and copulation success of colour ringed individuals. On this respect, they are quite unequal. Nevertheless, independantly of their copulation success, they all contribute in attracting the hens to the arena, and sometimes old surviving individuals signal to youngers where to join the arena. The success of the group relies on all of them. A population is not only the sum of a given number of anonymous consumers or reproducers. It is built of individuals each with its personality. Behaviour is necessary to elucidate the social network of interactions between individuals with personal profiles, life histories, skills and experience. Conservation requests informations from behavioural studies.