A team of researchers from Utrecht University and UK partners has provided the first scientific evidence that grey seals can injure dolphin species — not just porpoises — in the North Sea.The study, published in Diseases of Aquatic Organisms, suggests that grey seals may have a broader ecological impact on small cetaceans than previously recognised. The research was based on post-mortem examinations of four stranded dolphins: a bottlenose dolphin, a common dolphin, and two white-beaked dolphins. All four animals showed injuries consistent with grey seal bites. Detailed pathological and microbiological analyses supported these conclusions. Importantly, none of the dolphins died immediately from the attacks. Many of the wounds were several days to weeks old, indicating that the animals initially survived the encounters. However, they later succumbed to severe bacterial infections.
Some of the bacterial species identified were known to be specific to seals, strengthening the evidence that grey seals were responsible. This finding is particularly significant because it highlights a potential pathway for disease transmission between marine mammal species. The study underscores that grey seals may influence small cetacean populations not only through direct physical injury, but also indirectly through infection following attacks.
Traumatic injuries by grey seals on delphinids from northwest European waters
