Sometimes sperm whales (Physeter macrocephalus) cannot find their way back to the high seas: a multidisciplinary study on a mass stranding

• Published in: PloS one 2011-05, Vol.6 (5), p.e19417
• Main Authors: Mazzariol, Sandro, Di Guardo, Giovanni, Petrella, Antonio, Marsili, Letizia, Fossi, Cristina M, Leonzio, Claudio, Zizzo, Nicola, Vizzini, Salvatrice, Gaspari, Stefania, Pavan, Gianni, Podestà, Michela, Garibaldi, Fulvio, Ferrante, Margherita, Copat, Chiara, Traversa, Donato, Marcer, Federica, Airoldi, Sabina, Frantzis, Alexandros, Quirós, Yara De Bernaldo, Cozzi, Bruno, Fernández, Antonio
• Format: Article
• Language: English
• Subjects: Adipose tissue; Adipose Tissue - chemistry; Adipose Tissue - metabolism; Age determination; Analysis; Animal behavior; Animals; Aquatic mammals; Bacteriology; Behavior, Animal - physiology; Biology; Biopsy; Blood circulation; Cetacea; Chemical compounds; Chromatography; Chronology; Coastal environments; Coastal water temperatures; Contaminants; Disease susceptibility; Environmental Pollutants - chemistry; Environmental Pollutants - metabolism; Environmental science; Forensic medicine; Geography; Geomagnetic field; Geomagnetism; Handbooks; Histopathology; Human influences; Humans; Hygiene; Identification; Integrated approach; Isotopes; Italy; Lipophilic; Male; Mediterranean Sea; Metals, Heavy - chemistry; Metals, Heavy - metabolism; Meteorological Concepts; Morphology; Multidisciplinary research; Orientation - physiology; Pathology; Phocoena; Physeter; Physeter macrocephalus; Pollutants; Polymerase chain reaction; Public health; Seismic surveys; Solar cycle; Sperm Whale - anatomy & histology; Sperm Whale - physiology; Stable isotopes; Stranding; Tissues; Toxicology; Toxoplasma gondii; Veterinary medicine; Veterinary Science; Water temperature; Weather; Weather conditions; Whales; Whales & whaling; Xenobiotics
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0019417

Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Solar cycles and related changes in the geomagnetic field, variations in water temperature and weather conditions, coast geographical features and human activities have been proposed as possible causes. In December 2009, a pod of seven male sperm whales stranded along the Adriatic coast of Southern Italy. This is the sixth instance from 1555 in this basin. Complete necropsies were performed on three whales whose bodies were in good condition, carrying out on sampled tissues histopathology, virology, bacteriology, parasitology, and screening of veins looking for gas emboli. Furthermore, samples for age determination, genetic studies, gastric content evaluation, stable isotopes and toxicology were taken from all the seven specimens. The animals were part of the same group and determined by genetic and photo-identification to be part of the Mediterranean population. Causes of death did not include biological agents, or the "gas and fat embolic syndrome", associated with direct sonar exposure. Environmental pollutant tissue concentrations were relatively high, in particular organochlorinated xenobiotics. Gastric content and morphologic tissue examinations showed a prolonged starvation, which likely caused, at its turn, the mobilization of lipophilic contaminants from the adipose tissue. Chemical compounds subsequently entered the blood circulation and may have impaired immune and nervous functions. A multi-factorial cause underlying this sperm whales' mass stranding is proposed herein based upon the results of postmortem investigations as well as of the detailed analyses of the geographical and historical background. The seven sperm whales took the same "wrong way" into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. Seismic surveys should be also regarded as potential co-factors, even if no evidence of direct impact has been detected.