FLUCTUATIONS IN THE DUTCH BADGER MELES-MELES POPULATION BETWEEN 1960 AND 1990

The size of the Badger population in the Netherlands is estimated on t he basis of sett surveys in 1960, 1970, 1980 and 1990. The numbers of used important setts were 588, 640, 405 and 606, respectively. So ther e were strong fluctuations especially due to the drop (-36%) in 1980. In 1990 the number of used important setts nearly returned to the leve l of 1960. However, there were important regional differences. There w as a strong increase in areas with large woodlands, mainly in the cent ral part of the country. In the south, with more traffic, farming and urbanization, the numbers remained 20-30% lower than in 1960, despite the fact that traditionally these were the best Badger areas. Only 25% of the important setts used in 1960 were still in use in 1990. The gr owth of the number of collapsed or lost setts increased considerably d uring those 30 years, indicating a rather large sett turnover probably due to disturbance or a related stress factor. Some possible causes o f the fluctuations are discussed. It is recommended that a monitoring scheme be carried out every 2 or 3 years in some key areas, in order t o get a better idea of the short-term fluctuation range of the populat ion. For one-off, single-observation surveys, a simpler and more-robus t sett classification is desirable, based on the number of intact hole s, instead of on 'main setts'.