1. Department of Ecology and Evolutionary Biology, Princeton University, Guyot Hall, Princeton, NJ 08542, USA
2. ICREA-Movement Ecology Laboratory, Centre for Advanced Studies of Blanes (CEAB-CSIC), Cala St Francesc 14, Blanes 17300, Spain
3. Departamento de Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Lisboa 1749-016, Portugal
4. CREAF, Cerdanyola del Vallès, Barcelona 08193, Spain
5. Department of Physics and the Donnelly Centre, University of Toronto, 60 St George St., Toronto, Canada M5S1A7