May 2009

Focus on Argynnis niobe in the dunes of North Holland

Michiel Wallis de Vries (De Vlinderstichting)

The Niobe Fritillary (Argynnis niobe) has shown an alarming decline since 1997; it is now an endangered species in the Netherlands. As the coastal dunes constitute the species’ stronghold, we carried out a survey of the species distribution in the dunes of Kennemerland with the help of volunteers. The Niobe Fritillary was found in 42 out of 107 km squares investigated. Distribution has shrunk by more than 50% in the last two decades, and the survey suggests that the decline is continuing. More research is needed on host plant use in these calcareous dunes. It is clear, however, that the main cause of decline lies in the vast encroachment of tall grasses and scrub, especially Black Cherry (Prunus serotina), facilitated by low rabbit numbers. Extreme drought, such as in 2003, presents an additional threat. In several areas, restoration measures are being taken. Nectar and host plants will benefit from scrub clearance and creation of a more open vegetation. Hopefully, our monitoring schemes will reveal a recovery of this endangered butterfly in the coming years!