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

The size of the Badger population in the Netherlands is estimated on the basis of sett surveys in 1960, 1970, 1980 and 1990. The numbers of used important setts were 588, 640, 405 and 606, respectively. So there were strong fluctuations especially due to the drop (-36%) in 1980. In 1990 the number of used important setts nearly returned to the level of 1960. However, there were important regional differences. There was a strong increase in areas with large woodlands, mainly in the central 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 growth of the number of collapsed or lost setts increased considerably during those 30 years, indicating a rather large sett turnover probably due to disturbance or a related stress factor. Some possible causes of 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 to get a better idea of the short-term fluctuation range of the population. For one-off, single-observation surveys, a simpler and more-robust sett classification is desirable, based on the number of intact holes, instead of on 'main setts'.