Leopold Mardik F, Begeman Lineke, van Bleijswijk Judith D L, IJsseldijk Lonneke L, Witte Harry J, Gröne Andrea
Department of Ecosystems, Wageningen IMARES, PO Box 167, 1790 AD, Den Burg, Texel, The Netherlands
Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands.
Proc Biol Sci. 2015 Jan 7;282(1798):20142429. doi: 10.1098/rspb.2014.2429.
Harbour porpoises (Phocoena phocoena) stranding in large numbers around the southern North Sea with fatal, sharp-edged mutilations have spurred controversy among scientists, the fishing industry and conservationists, whose views about the likely cause differ. The recent detection of grey seal (Halichoerus grypus) DNA in bite marks on three mutilated harbour porpoises, as well as direct observations of grey seal attacks on porpoises, have identified this seal species as a probable cause. Bite mark characteristics were assessed in a retrospective analysis of photographs of dead harbour porpoises that stranded between 2003 and 2013 (n = 1081) on the Dutch coastline. There were 271 animals that were sufficiently fresh to allow macroscopic assessment of grey seal-associated wounds with certainty. In 25% of these, bite and claw marks were identified that were consistent with the marks found on animals that had tested positive for grey seal DNA. Affected animals were mostly healthy juveniles that had a thick blubber layer and had recently fed. We conclude that the majority of the mutilated harbour porpoises were victims of grey seal attacks and that predation by this species is one of the main causes of death in harbour porpoises in The Netherlands. We provide a decision tree that will help in the identification of future cases of grey seal predation on porpoises.
港湾鼠海豚（Phocoena phocoena）在北海南部大量搁浅，身上有致命的边缘锋利的伤痕，这在科学家、渔业和环保人士之间引发了争议，他们对可能的原因看法不一。最近在三只受伤的港湾鼠海豚的咬痕中检测到灰海豹（Halichoerus grypus）的DNA，以及对灰海豹攻击鼠海豚的直接观察，已确定这种海豹是一个可能的原因。在对2003年至2013年间在荷兰海岸搁浅的死亡港湾鼠海豚（n = 1081）照片的回顾性分析中，对咬痕特征进行了评估。有271只动物足够新鲜，可以确定地对与灰海豹相关的伤口进行宏观评估。其中25%的动物身上发现了咬痕和爪痕，与检测出灰海豹DNA呈阳性的动物身上发现的痕迹一致。受影响的动物大多是健康的幼崽，它们有厚厚的脂肪层，且最近进食过。我们得出结论，大多数受伤的港湾鼠海豚是灰海豹攻击的受害者，该物种的捕食是荷兰港湾鼠海豚死亡的主要原因之一。我们提供了一个决策树，将有助于识别未来灰海豹捕食鼠海豚的案例。
