Abstract

(…) gray seal (Halichoerus grypus) consumption of harbor porpoises—whether predation or scavenging—might reflect a change in gray seal feeding habits in the southern North Sea (Haelters et al. 2012), where these two species co-occur (Kiszka et al. 2004, Vincent et al. 2005, Harkonen et al. 2007, Hammond et al. 2013). In fact, porpoise predation by gray seals might be a more widespread phenomenon. Since 2003, dozens of cases
of dead porpoise stranded along the Dutch coast may have been killed or scavenged by gray seals every year, based on post mortem examinations and predator identification criteria proposed by Haelters et al. in 2012.

Here, we provide direct observations of gray seal predation and scavenging on harbor porpoises in the Strait of Dover (eastern English Channel), off the coast of France in the eastern English Channel (Fig. 1). Two observations were made from the cliffs (up to 45 m above sea level) of Cap Gris-Nez, while the third was made inside the fishing harbor of Boulogne-sur-Mer (50º43.41′N, 1º36.03′E; Fig. 1). We also describe possible predation or scavenging based on external body observations made on two harbor porpoises freshly stranded in January and March 2012 on the northern French coast. (…)