University of Veterinary Medicine Hannover Institute for Terrestrial and Aquatic Wildlife Research Predation of marine mammals by grey seals (Halichoerus grypus) – Assessment of the background, the extent and the potential effects on the ecosystem Prädation mariner Säugetiere durch Kegelrobben (Halichoerus grypus) – Untersuchungen zu den Hintergründen, dem Ausmaß und den potentiellen Effekten auf das Ökosystem INAUGURAL DOCTORAL THESIS in partial fulfilment of the requirements of the degree of Doctor of Natural Sciences - Doctor rerum naturalium - (Dr. rer.nat.) submitted by Abbo van Neer, MConBio Norden, Ostfriesland Büsum 2019 Scientific supervision: Prof. Prof. h. c. Dr. Ursula Siebert, Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation Prof. Dr. Gerd Bicker, Institute for Physiology and Cell Biology University of Veterinary Medicine Hannover, Foundation 1st supervisors: Prof. Prof. h. c. Dr. Ursula Siebert, Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation Prof. Dr. Gerd Bicker, Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation Prof. Dr. Rune Dietz 2nd supervisor: …………………………………………… 07. Mai 2019 Day of the oral examination: …………………………………………… I The present dissertation was carried out as part of the projects "Pilotstudie zur Erfassung von Kegelrobbenrissen bei marinen Säugetieren in der deutschen Nordsee" and "Umfassende weiterführende Untersuchungen zur Kegelrobbenprädation auf marine Säugetiere in deutschen Gewässern" (Funded by the Ministry of Energy, Agriculture, the Environment, Nature and Digitalization Schleswig-Holstein, Germany). Results of the dissertation were published in the following articles: van Neer, A., Jensen, L.F., Siebert, U. (2015). Grey seal (Halichoerus grypus) predation on harbour seals (Phoca vitulina) on the island of Helgoland, Germany. Journal of Sea Research 97, 1–4. https://doi.org/10.1016/j.seares.2014.11.006 This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland as well as during necropsies. Further, I primarily wrote the manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. Heers, T., van Neer, A., Becker, A., Grilo, M. L., Siebert, U., & Abdulmawjood, A. (2017). Loop-mediated isothermal amplification (LAMP) assay—A rapid detection tool for identifying red fox (Vulpes vulpes) DNA in the carcasses of harbour porpoises (Phocoena phocoena). PLOS ONE, 12(9), e0184349. https://doi.org/10.1371/journal.pone.0184349 My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic, as well as any samples of marine mammals and foxes used. Further, I participated in writing the manuscript and was involved in funding acquisition. Heers, T., van Neer, A., Becker, A., Gross, S., Hansen, K. A., Siebert, U., & Abdulmawjood, A. (2018). Loop-mediated isothermal amplification (LAMP) as a confirmatory and rapid DNA detection method for grey seal (Halichoerus grypus) predation on harbour porpoises (Phocoena phocoena). Journal of Sea Research 140, 32–39. https://doi.org/10.1016/j.seares.2018.07.008 My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic, as well as any samples of marine mammals used. Further, I participated in writing the manuscript and was involved in funding acquisition. van Neer, A., Gross, S., Kesselring, T., Wohlsein, P., Leitzen, E., & Siebert, U. (2019). Behavioural and Pathological Insights into a Case of Active Cannibalism by a Grey Seal (Halichoerus grypus) on Helgoland, Germany Journal of Sea Research, 148–149, 12–16. https://doi.org/10.1016/j.seares.2019.03.004 This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland. Further, I primarily wrote the manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. Further results of the dissertation are to be published in the following articles: van Neer, A., Gross, S., Kesselring, T., Grilo, M., Ludes-Wehrmeister, E., Roncon, G., & Siebert, U. (in preparation). Putting together the pieces of the puzzle - Part I - Assessing seal carcasses potentially subjected to grey seal (Halichoerus grypus) predation. This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland II as well as during necropsies. Further, I primarily wrote the manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. van Neer, A., Gross, S., Kesselring, T., Grilo, M., Ludes-Wehrmeister, E., Roncon, G., & Siebert, U. (in preparation). Putting together the pieces of the puzzle - Part II - Assessing harbour porpoise carcasses potentially subjected to grey seal (Halichoerus grypus) predation. This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland as well as during necropsies. Further, I primarily wrote the manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. The following parts of the dissertation were also presented at international conferences or in the form of a letter and a report van Neer, A., Jensen, L. F., Blädel, R., & Siebert, U. (2014). If you can’t beat them, eat them - Behavioural observations of grey seal (Halichoerus grypus) and harbour seal (Phoca vitulina) interactions on the island of Helgoland, Germany. In 28th Conference of the European Cetacean Society, 05.-09.04.2014. Liège, Belgium. (Abstract und Poster; Winner of the prize “Best scientific poster 2014”) This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland as well as during necropsies. Further, I primarily wrote the respective manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. van Neer, A., Wohlsein, P., & Siebert, U. (2015). Shedding light on the phenomenon of grey seal predation on marine mammals In 29th Conference of the European Cetacean Society, 23.-25.03.2015. St Julian’s, Malta. (Abstract und Poster; Winner of the prize “Best scientific poster 2015”) This work was primarily conducted by myself. My participation in this study involved the provisioning of the necessary conceptual background with regards to the topic and the collection of data on Helgoland as well as during necropsies. Further, I primarily wrote the respective manuscript, but in collaboration with the named co-authors and was involved in funding acquisition. ICES. (2017). Report of the Workshop on Predator-prey Interactions between Grey Seals and other marine mammals (WKPIGS). Middelfart, Denmark: (N. Hanson, A. van Neer, A. Brownlow, & J. Haelters). Available under http://www.ices.dk/sites/pub/Publication Reports/Expert Group Report/SSGEPD/2017/01 WKPIGS - Report of the Workshop on Predator-prey Interactions between Grey Seals and other marine mammals.pdf This report summarises the findings resulting from the respective workshop which was organised by the named people as part of the 31st Conference of the European Cetacean Society in Middelfart, Denmark. My participation in this workshop involved the initiation, collaborative organisation of the event, chairing of and presenting in sessions, collation and evaluation of the joint European data as well as the acquisition of the funding. Further, I contributed major parts to the manuscript. Haelters, J., Kerckhof, F., van Neer, A., & Leopold, M. (2015). Letter to the Editor Exposing Grey Seals as Horses and Scientists as Human. Aquatic Mammals, 41(3), 351–353. https://doi.org/10.1578/AM.41.3.2015.351 My participation in this publication involved the collaborative scientific and creative conception and writing of the manuscript. III Table of contents 1. Background ........................................................................................................... 1 The phenomenon of grey seal predation on marine mammals ................................ 2 2. The first report of grey seal predation on marine mammals in German waters ..... 4 Grey seal (Halichoerus grypus) predation on harbour seals (Phoca vitulina) on the island of Helgoland, Germany .................................................................................. 4 3. Characterisation of grey seal induced lesions in marine mammal carcasses and associated behaviour ................................................................................................. 14 a. Behavioural and Pathological Insights into a Case of Active Cannibalism by a Grey Seal (Halichoerus grypus) on Helgoland, Germany ....................................... 14 b. Putting together the pieces of the puzzle – Part I - Assessing seal carcasses potentially subjected to grey seal (Halichoerus grypus) predation .......................... 28 c. Putting together the pieces of the puzzle - Part