Do 'rogue' seals exist? Implications for seal conservation in the UK

Abstract

The management of conflict between people and large carnivores frequently focuses on the selective removal of the so-called 'problem' or 'rogue' animals. However, the existence of such individuals has rarely been examined. Recent management of seal-salmon fishery conflict in Scotland follows this approach, and under the Moray Firth Seal Management Plan the lethal removal of perceived problem individuals is permitted in salmon rivers. However, the efficacy of this strategy depends on (1) the existence of river-specialist individuals; (2) these individuals having a greater per capita impact on salmon fisheries than individuals in the general population. Using data collected in three rivers from March 2005 to February 2008, we show using photo-identification that a small fraction of the population (≤1%) comprises individual seals that specialize in using rivers. This behaviour was more pronounced for grey seals Halichoerus grypus than harbour seals Phoca vitulina, and a greater proportion of individual harbour seals were seen only once during the study. A higher percentage of digestive tract samples collected from seals in rivers tested positive for salmon and trout DNA compared with seal scats collected at coastal sites, although the sample size was small. These results indicate that targeting individual seals present in rivers is more likely to remove those individuals consuming salmon, and have a larger per seal benefit to salmon compared with targeting seals hauled out in estuaries. This lends rare scientific support to the established management paradigm of problem-individual removal. © 2011 The Authors. Animal Conservation © 2011 The Zoological Society of London.