Behavioural and pathological insights into a case of active cannibalism by a grey seal (Halichoerus grypus) on Helgoland, Germany

First reports on cases of grey seal predation on other marine mammals from different parts of Europe have been published in recent years, but few cases provide sufficient detail. Here we report a case of active cannibalism by a grey seal, which has been witnessed and recorded in detail on the German island of Helgoland, describing particular behavioural aspects and lesions. In March 2018, a subadult male grey seal was observed catching, killing and feeding extensively from a juvenile grey seal. The carcass showed severe cutaneous lacerations, starting in the head region and following around the trunk in a circular pattern. These results are discussed with regard to the previously reported cases to form a solid knowledge base for retrospective and future assessments of carcasses potentially subjected to grey seal predation. The correct assignment of predated seals is important to determine the potential influence this behaviour may have on seal populations.