Defining predator foraging ranges, illustrated using Adélie penguin foraging tracks from Mawson coast

One step toward defining small-scale management units is to determine the areas most likely to be foraged by predators from one year to the next, i.e. what is a predator’s feeding range taking into account interannual variation in foraging locations? This paper considers the issues to be addressed in answering that question. The proposed method for defining foraging ranges is based on an approach used to define fishing grounds. The data which is considered as an example here consists of location/time recordings from a satellite tracking system. This data is used to generate a map of feeding effort and this is used to delineate a feeding ground for Adélie penguins on the Mawson coast in eastern Antarctica. This method builds on existing methods but incorporates tools for pooling information across colonies, years, and species to define individual species and pooled foraging ranges. The establishment of these foraging ranges for the purposes of small-scale management units may need to be examined in three parts. The first part is to determine whether the results would be different for different seasons e.g. summer vs winter. The second part is to establish the combined foraging ranges across a number of species for which tracking information is available – pooled foraging ranges. The third consideration is whether some species with low colony biomass have large proportions of their foraging ranges falling outside of the specified pooled foraging ranges. If this makes those species vulnerable in the management process then consideration will need to be given to including those ranges as special extensions to the foraging grounds. Thus, a comparison of foraging ranges for individual species with the pooled foraging range would be a useful step in this process.