Optimal migration strategies in animals that run:: a range equation and its consequences

Optimal migration theory depends to a large extent on the range equation, that is, a function relating potential distance moved to fuel load. Such range equations derived from aerodynamic principles exist for birds. I derive an analogous range equation for animals that run based on biomechanical principles. The range for animals that run is proportional to ln(1/+f), where f is the relative fuel load at departure and relates the mass at departure (m) to the lean mass (m(o)) as m=(1+f) m(o). Predictions pertaining to migration decisions, such as optimal stopover duration, fuel load and detours around barriers, can thereby be made for animals other than birds. I hope this paper will stimulate further experimental tests regarding migration decisions in suitable animal systems. (C) 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.