Indication of lethal interactions between a solitary bottlenose dolphin ( Tursiops truncatus ) and harbor porpoises ( Ph
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Gross et al. BMC Zoology (2020) 5:12 https://doi.org/10.1186/s40850-020-00061-7
RESEARCH ARTICLE
Open Access
Indication of lethal interactions between a solitary bottlenose dolphin (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) in the German Baltic Sea Stephanie Gross1* , Philip Claus1, Peter Wohlsein2, Tina Kesselring1, Jan Lakemeyer1, Anja Reckendorf1, Marco Roller1, Ralph Tiedemann3 and Ursula Siebert1
Abstract Background: Aggressive interactions between bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) have been reported in different parts of the world since the late 1990s. In the Baltic Sea, harbor porpoises are the only native cetacean species, while bottlenose dolphins may appear there temporarily. In the fall of 2016, a solitary male photo-identified bottlenose dolphin stayed in the German Baltic Sea of SchleswigHolstein for 3 months. During that time, the necropsies of the stranded harbor porpoises revealed types of trauma of varying degrees in six animals, which is unusual in this area. The purpose of this study was to determine if the appearance of the bottlenose dolphin could be linked to the trauma of the harbor porpoise carcasses. Results: Pathological findings in these animals included subcutaneous, thoracic and abdominal hemorrhages, multiple, mainly bilateral, rib fractures, and one instance of lung laceration. These findings correspond with the previously reported dolphin-caused injuries in other regions. Moreover, public sighting reports showed a spatial and temporal correlation between the appearance of the dolphin and the stranding of fatally injured harbor porpoises. Conclusion: Despite the fact that no attack has been witnessed in German waters to date, our findings indicate the first record of lethal interactions between a bottlenose dolphin and harbor porpoises in the German Baltic Sea. Furthermore, to our knowledge, this is the first report of porpoise aggression by a socially isolated bottlenose dolphin. Keywords: Cetaceans, Interspecific aggression, Porpicide, Blunt trauma, Mortality, Stranding
Background The distributions of bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) overlap in several areas of the Northern Hemisphere [1, 2]. In one of these areas, namely the Moray Firth, Scotland, aggressive bottlenose dolphin interactions with harbor * Correspondence: [email protected] 1 Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Werftstrasse 6, 25761 Büsum, Germany Full list of author information is available at the end of the article
porpoises were originally reported [3]. Four witnessed dolphin attacks resulted in multiple skeletal fractures and damaged internal organs in harbor porpoises. Moreover, tooth marks were found as several parallel wounds on the skin of some of the carcasses. The spacing of these so-called rake marks were determined to be specific for bottlenose dolphins. Similar cases were noticed in Cardig
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