Abstract
As a follow-up on the data presented for seals, we herein report and discuss outcomes resulting from a retrospective evaluation of harbour porpoise stranding and necropsy data from Schleswig–Holstein, Germany (n = 4463) to enable an objective evaluation of potential ecological effects of grey seal predation on porpoises. Results are compared to a recent case of definite grey seal predation as well as to reports from other countries. Porpoise carcasses potentially subject to grey seal predation show severe lacerations, with large parts of skin and underlying tissue being detached from the body. Loss of blubber tissue is common. Based on the occurrence frequencies of encountered lesions, a list of parameters as well as a complementary decision tree are suggested to be used for future assessments. The results shown add to an increasingly standardised assessment protocol of suspected grey seal predation cases making respective results comparable between different areas and countries. The usage of a standardised protocol may increase the awareness of grey seal predation and the reporting of such cases. By this, differences in the predation and feeding patterns as well as the potential ecological relevance of this behaviour may be elucidated.
Highlights
As a follow-up on the data presented for seals, we report and discuss outcomes resulting from a retrospective evaluation of harbour porpoise stranding and necropsy data from Schleswig–Holstein, Germany (n = 4463) to enable an objective evaluation of potential ecological effects of grey seal predation on porpoises
It was shown that this behaviour is not restricted to specific regions but potentially occurs throughout the North Sea and b eyond[9], with porpoises and harbour and grey seals being utilised as p rey[10,11,12]
Between 1990 and the end of 2018, data on 4463 harbour porpoise carcasses were recorded in the necropsy and stranding database of Schleswig–Holstein, at the Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Germany and are available for a retrospective evaluation
Summary
Published descriptions of gross pathological examinations of porpoise carcasses include trauma-induced lesions with large areas of detached skin and blubber, canine puncture wounds throughout the lesions and parallel bite and scratch marks in the skin[1,2,6,13]. Based on these observations, a retrospective analysis of the Dutch stranding database indicated that at least 17% of stranded porpoises were likely to have died as a result of grey seal predation, making it one of the most frequent causes of death[13]. Results are discussed in comparison to a definite case of predation as well as to cases reported in the literature and other origins of trauma such as scavenging or predation by foxes (Vulpes vulpes)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call