The little-known Ginkgo-toothed whale has a wider range than previously understood, extending into the frigid waters of the North Pacific. Cetaceans are widely known as fully aquatic animals that include whales, dolphins, and porpoises. Cetaceans include more than 90 existing species, divided into baleen whales (Mysticeti) and toothed whales (Odontoceti). Specifically, toothed whales are characterized by their teeth and include a variety of different species, including the lesser-known genus Mesoplodon.
These animals typically inhabit offshore waters and rarely surface, so their distribution and ecology are relatively unknown.
A research team composed of Mika Kuroda, assistant professor at the Northern Biosphere Field Science Center of Hokkaido University, and Takashi Matsuishi-Fritz, a professor at the School of Fisheries Science, recently reported that a stranded ginkgo-toothed whale was found off the Yakumo coast in southern Hokkaido. Their findings were published in the journal Aquatic Mammals.
"With more than 15 known species, the genus Beaked Whale is the largest genus in the family Beaked Whale," Kuroda explains. Different species of the genus can be identified by the shape of their heads and the special teeth of the males. The male of the ginkgo-toothed beaked whale - Mesoplodonginkgodens - has 10cm wide teeth shaped like the leaves of a ginkgo tree.
Nearly everything scientists know about Ginkgo-toothed whales comes from 95 individuals in 88 whale strandings. Among them, 30 strandings occurred across Japan.
On February 4, 2022, a whale stranded in Yakumo Town, Hokkaido. The whale carcass was sent to the Hakodate Fisheries and Marine Research Center for measurements and necropsy. The whale is a male, 477 centimeters long, and is in an early stage of decay, indicating that it has been dead for some time. Its morphology is consistent with M.ginkgodens; furthermore, genetic analysis of mitochondrial DNA places the specimen into the M.ginkgodens clade, which shares an identical sequence.
Previous strandings have occurred in many places, including Japan, the U.S. West Coast, Australia, the Galapagos Islands, Thailand, New Zealand, Micronesia, the Marshall Islands, China, South Korea and Mexico - all in temperate, subtropical and tropical waters. This study is the first report of a ginkgo-toothed beaked whale in the cold waters of the North Pacific.
Kuroda said: "Another stranding of a possible Ginkgo-toothed whale was reported on November 29, 2021, but the specimen was lost due to bad weather. Our results indicate that these whales may have migrated near Hokkaido during the winter."
Compiled source: ScitechDaily