ORIGINAL PAPER Prevalence of skull pathologies in European harbor seals (Phoca vitulina) during 1981–2014 Cino Pertoldi 1,2 & Lasse Fast Jensen 1 & Aage Kristian Olsen Alstrup 3 & Ole Lajord Munk 3 & Trine Bæk Pedersen 1 & Christian Sonne 4 & Rune Dietz 4 & Tobias Daugaard-Petersen 4 & Hanne Ellen Kortegaard 5 & Morten Tange Olsen 6 & Karin Charlotte Hårding 7 & Trine Hammer Jensen 1,2 Received: 16 August 2017 /Accepted: 11 October 2017 /Published online: 23 October 2017 # Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland 2017 Abstract Harbor seals (Phoca vitulina) inhabit the seas surrounding Denmark and are an important top predator in the marine food chain. This trophic position exposes them to environmental contaminants with disease epi- demics and hunting being additional threats to this popu- lation. It is therefore important to study how environmen- tal pollution at the current order of magnitude affects the health of the population. Earlier studies have shown that occurrence of periodontitis could be linked to the amount of pollution the seals were subjected to. In order to inves- tigate this further, 380 skulls and 141 mandibles of harbor seals (Phoca vitulina) from the Wadden Sea, the Limfjord, and Kattegat collected during the period 1970–2014 were examined. The skulls were examined for pathological le- sions. The Hounsfield Units (HU) which are correlated to the bone mineral density (BMD) were measured in a sub- sample ( n = 34) using CT scans. The macroscopic examination revealed (with the exception of the Swedish part of Kattegat) a significant increase of pathological lesions over the study period of 1981–2014. The exami- nation of HU showed that median HU measured at mul- tiple sites was highest in the healthy skulls compared to the skulls with one or more of the lesions. A discriminant analysis allowed high discriminatory capacity to separate healthy skulls from the skulls with pathologies, simply by the utilization of the HU data. Former studies of BMD in marine mammals have shown that exposure to environ- mental chemicals alter BMD and cause periodontitis. The present study, based on temporal and spatial trends in BMD, confirms the results of previous studies. Keywords Hounsfield units . Mineral-bone-density . CT scans . Exostosis . Periodontitis . Foramina Cino Pertoldi and Lasse Fast Jensen contributed equally to this work. Communicated by: Karol Zub Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13364-017-0340-2) contains supplementary material, which is available to authorized users. * Cino Pertoldi cp@bio.aau.dk 1 Section of Biology and Esnvironmental Science, Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, DK, 9220 Aalborg East, Denmark 2 Aalborg Zoo, Mølleparkvej 63, DK, 9000 Aalborg, Denmark 3 Department of Nuclear Medicine and PET Center, Nørrebrogade 44, 10C, DK, 8000 Aarhus C, Denmark 4 Faculty of Science and Technology, Department of Bioscience, Arctic Research Centre (ARC), Aarhus University, Frederiksborgvej 399, PO Box 358, DK, 4000 Roskilde, Denmark 5 Department of Veterinary Clinical and Animal Sciences, Dyrlægevej 16,, DK, 1870 Frederiksberg C, Denmark 6 Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK, 1350 Copenhagen K, Denmark 7 Department of Biological and Environmental Sciences, Gothenburg University, Box 461, SE, 405 30 Gothenburg, Sweden Mamm Res (2018) 63:55–63 https://doi.org/10.1007/s13364-017-0340-2