1. Behavioural Ecology Group; Wageningen University and Research; De Elst 1 6708 WD Wageningen The Netherlands
2. Department of Animal Ecology; Netherlands Institute of Ecology (NIOO-KNAW); Droevendaalsesteeg 10 6708 PB Wageningen The Netherlands
3. Department of Biometris; Wageningen University and Research; Droevendaalsesteeg 1 6708 PB Wageningen The Netherlands