Conceptual and methodological issues in the comparative study of collective group movements.

In our commentary, we highlight several conceptual and methodological problems that have hampered broader integration of studies of collective group movements. Specifically, we argue that studies of captive animals should only be used to elucidate behavioural mechanisms. Moreover, the diversity of physical environments in which group movements occur as well as the social diversity of groups deserve more consideration in integrative studies. Furthermore, tests of predictions based on modelling studies are often hampered by the fact that models include variables that are difficult or impossible to measure in real animals. We also advocate the use of an empirical, rather than subjective establishment of operational definitions of group movements and the associated individual roles. Finally, we emphasize the utility of controlled experiments in the study of collective decision-making and group movements and encourage their wider application. Copyright (c) 2010 Elsevier B.V. All rights reserved.