Pathological findings and probable causes of the death of Stejneger’s beaked whales (Mesoplodon stejnegeri) stranded in Japan from 1999 and 2011

One hundred and twenty stranding events of Stejneger’s beaked whales were reported in Japan between 1999 and 2011. The purpose of this study is to introduce pathological data and to discuss probable causes of death for 44 Stejneger’s beaked whales among them. The significant pathological findings were the pulmonary edema, parasitic granulomatous nephritis, emaciation, amyloidosis, suppurative bronchopneumonia and so on. The probable causes of death were categorized as noninfectious in 43 of the cases, which included drowning, starvation and secondary amyloidosis. One individual was diagnosed with septicemia, which was the only example of an infectious disease. Because we could not always perform advanced analyses, such as microbiology tests, biotoxin examinations or contaminant analyses, the finality of our findings may be impaired. However, the present study has broad implications on the causes of death of Stejneger’s beaked whales of the seas around Japan, which are valuable for the future studies and for the detection of emerging diseases.