Food for thought: Harbor porpoise foraging behavior and diet inform vulnerability to disturbance

Abstract

Research has shown that noise disturbance can disrupt the behavior of harbor porpoises. The significance of such disturbance is unclear. However, these animals may be vulnerable to starvation when disturbed due to their high energy requirements. Important parameters determining harbor porpoise energy balance are the size and energy content of prey, their foraging behavior and their energetic requirements for homeostasis, growth, and reproduction. Energy intake can be estimated using published data from tagged animals. Such analysis indicates a broad range of plausible levels of energy intake, in line with those from captive studies. Metabolizable energy intake estimates were most strongly affected by variations in target prey size and to a lesser extent, by the foraging intensity of porpoises. In all but the worst case scenarios, harbor porpoises are well equipped for their ecological niche due to their generalist diet, consisting of a range of moderate to high energy-density prey combined with ultra-high foraging rates and high capture success. If animals can find suitable prey, porpoises may be capable of recovering from some lost foraging opportunities. Minimizing disturbances is, however, important for their health. Further research into prey and the environment are required to fully test the assumption of vulnerability.