1. Evolution, Behaviour and Environment, School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
2. School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK
3. Instituto Regional de Investigación y Desarrollo Agroalimentario y Forestal de Castilla La Mancha (IRIAF), CIAPA de Marchamalo, 19180 Guadalajara, Spain
4. Centre for Research in Animal Behaviour, Psychology, University of Exeter, Exeter EX4 4QG, UK