Meeting Abstract
The net cost of pedestrian transport on the flat (NCOT; energy expended kg-1 m-1) is lower for larger animals while smaller animals gain an energetic advantage uphill. Other factors so far investigated describe NCOT at best weakly: number of limbs is not predictive while there is some suggestion of a negative effect of temperature and of a waddling gait. Furthermore, although moving faster along the ground requires a higher rate of energy expenditure, for most terrestrial species this rate scales linearly with speed on the flat and thus NCOT is invariant of speed. Therefore, total transport costs, at least for terrestrial animals, appear to be explained mainly by the physical costs of raising and moving the body a given distance, which is broadly described by mass. However, in certain terrestrial species, and in flying and swimming species, the NCOT-speed relationship is not a constant. From an energetics perspective, when minimising energy expenditure is the priority, presumably the default speed of locomotion for such species minimises NCOT. However, this speed may vary with factors such as substrate properties, substrate angle, load carrying and weather conditions (e.g. wind), and furthermore these factors may interact with each other and body mass. Together, these factors create an animal’s ‘energy landscape’. Additionally, the energy cost of locomotion associated with changing direction can be substantial and have implications for an animal seeking to minimise NCOT; their default direction of movement should be to continue in a straight line. Animals should be expected to adapt their speeds and movement patterns to their energy landscape, to attenuate the effects of the environment and other factors on their transport costs. Thus the energy landscape should influence, in predictable ways, not only an animal’s speed of locomotion but also the routes that it takes while travelling through its environment.
