Sperm whale carcass stranding on the shores of Niigata Prefecture in Japan

On February 1, 2025, the bones of a sperm whale (Physeter macrocephalus) were beached on Kakizaki Beach in Joetsu City.This was followed by the discovery of a decomposed carcass of a male sperm whale on February 27 on Yoneyama Beach in Kashiwazaki City (both in Niigata Prefecture).The bones and carcass were considered to belong to the same individual.The beached bones included those of the cranium, left maxilla, right mandible, sternum, left first rib, and a piece of bone of unknown origin.Five caudal vertebrae were removed from the carcass at Yoneyama Beach.Based on the lengths of these bones, the whale was estimated to be 15.6-16.7 m long.Few instances of sperm whales stranding ashore or being sighted in the Sea of Japan have been reported.Records dating back to 1901 show only two cases of stranded carcasses (including this one) and four sightings of swimming whales.The whale in this case was assumed to have died from unknown causes with the body decomposing adrift.Subsequently, the bones may have been separated by high waves, stranding some on shore.The bones (excluding the maxilla) were stored at the Joetsu Science Museum.The remaining carcasses were buried at each site.