Bat colonies continue to recover

07/01/2002 10:00

The number of bats in the Netherlands has increased in the last ten years. All seven species of bat which have been monitored on a long-term basis are doing well. Not much is known about the many other species that hibernate in hollow walls of buildings in urban areas or hollow trees. These species are not included in the counts.

Wintering bats (1990 = 100)

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Most species of bats in the Netherlands were having a hard time in the middle of the last century. Some species even disappeared altogether. There were a number of reasons for this deterioration: the use of insecticides in agriculture, the removal of wooded banks - which made it more difficult for bats to get their bearings - and the sealing off or disturbance of summer and winter residences.

In the 1950s one species (Daubenton’s bat) started to increase again. The other species began to recover in the mid 1980s. The population of the greater mouse-eared bat has developed slightly differently from the others, in that it has stabilised in the last five years. Many pond bats winter in urban areas; it is not clear whether these urban populations are also increasing. Protection of the locations where bats spend the winter has contributed to their increase.

Ben Daemen (CBS) , Marcel Straver (CBS) and Vilmar Dijkstra (VZZ)