DYNAMICS OF A BLACK GROUSE (TETRAO TETRIX) POPULATION IN THE FRENCH MARITIME ALPS

Abstract

The populations of the Eurasian black grouse Tetrao tetrix show different patterns of variability in different parts of Europe, at cause of the complex interplay between endogenous and exogenous factors on the regulation of population growth rates. In this study, a black grouse population was censused annually during autumn by the same observer in southern Alps, within the Tende’s shooting ground (French department of Alpes Maritimes). During the 31-year study period (1967 – 1997), the population abundance index remained constant as assessed by TRIM (Trends and Indices from Monitoring Data) analysis. In addition, this population did not show signs of regular cyclicity (i.e. statistically periodicity), as it has been observed in other southern populations of black grouse. Simulation tests and autoregressive moving average (ARMA) modeling showed that direct density dependence was responsible for about 40% of the variation in population growth rates, while the total amount of spring rainfall (April – June) explained 10% of the variability due to exogenous factors. The hunting pressure, that was reduced since 1974, and the creation of a national protected area adjacent to the study site in 1979, showed no significant effect on the black grouse population, that apparently was already fluctuating near its environmental carrying capacity.