The ginkgo-toothed beaked whale (Mesoplodon ginkgodens) is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for males not having any scarring.[3]
A ginkgo-toothed beaked whale skull located at the Okinawa Churaumi Aquarium, Japan.
Ginkgo-toothed beaked whales are more robust than most mesoplodonts, but otherwise look fairly typical. Halfway through the jaw, there is a sharp curve up where the ginkgo leaf-shaped tooth is.
The coloration is overall dark gray on males with light patches on the front half of the beak and around the head, and small white spots on the bottom of the tail, but the location may be variable. Females are a lighter gray and have countershading.
Both sexes reach 4.9 metres (16 feet) in length. They are around 2.4 metres (7.9 feet) long when born.
In June 2024, scientists aboard Research Storm, a research vessel, detected a pair of juvenile beaked whales off the coast of Baja California.[10] A skin sample taken from the pair later confirmed this as the first known at-sea sighting of this species of beaked whale.[11]
Behavior
Unlike all other known members of Ziphiidae, there is no evidence that the males engage in combat, although this may be due to a limited sample size. The species probably feeds primarily on squid.[12] The whales are shy, wary of boats, and spend almost all of their time foraging in the deep, coming up for air for a few minutes before descending again.
The whales' call has a distinct acoustic signature, known as BW43.[11]
Conservation
Until 2024, the only known observations of this species while alive came from hunters off the coasts of Japan and Taiwan, who occasionally take an individual. They are also affected by drift gillnets. One individual, identified from a DNA sample, was known to have interacted with a pelagiclongline fishery in the central and western Pacific Ocean. The ginkgo-toothed beaked whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[13]
The whales are particularly sensitive to sonar which disrupts their foraging and can cause them to ascend too quickly resulting in a form of decompression sickness.[10]
Specimens
In June 2024, 2 specimens were found in Baja California by tracking the previously unidentified whale song BW43.[14]
↑Nishiwaki, M.; Kasuya, T.; Kureha, K.; Oguro, N. (1972). "Further comments on Mesoplodon ginkgodens"(PDF). Scientific Reports of the Whales Research Institute. 24: 43–56. Retrieved 26 February 2019.
↑Dalebout, Merel Louise (2002). Species identity, genetic diversity, and molecular systematic relationships among the Ziphiidae (beaked whales). ProQuest: The University of Auckland (New Zealand). p.249.
↑Rosso, Massimiliano; Lin, Mingli; Caruso, Francesco; Liu, Mingming; Dong, Lijun; Borroni, Anna; Lin, Wenzhi; Tang, Xiaoming; Bocconcelli, Alessandro; Li, Songhai (2 December 2020). "First live sighting of Deraniyagala's beaked whale (Mesoplodon hotaula) or ginkgo-toothed beaked whale (Mesoplodon ginkgodens) in the western Pacific (South China Sea) with preliminary data on coloration, natural markings, and surfacing patterns". Integrative Zoology. 16 (4): 451–461. doi:10.1111/1749-4877.12507. PMID33289310. S2CID227947326.
Encyclopedia of Marine Mammals. Edited by William F. Perrin, Bernd Wursig, and J.G.M Thewissen. Academic Press, 2002. ISBN0-12-551340-2
Sea Mammals of the World. Written by Randall R. Reeves, Brent S. Steward, Phillip J. Clapham, and James A. Owell. A & C Black, London, 2002. ISBN0-7136-6334-0
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