Ginkgo-toothed beaked whale

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.

Description

File:Mesoplodon ginkgodens by OpenCage.jpg

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.

Unlike other species such as Blainville's beaked whale and Andrews' beaked whale, the teeth do not arch over the rostrum. The beak itself is of a moderate length.

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 in length. They are around long when born.

Population and distribution

This beaked whale has had fewer than 20 strandings off the coasts of Japan, Taiwan, California, the Galapagos Islands, New South Wales, New Zealand, Sri Lanka, the Maldives and the Strait of Malacca. Its range is essentially tropical and temperate waters in the Indian and Pacific Ocean. There are currently no population estimates.

A potential sighting occurred in the South China Sea in May 2019, although it was possible the sighted whales were Deraniyagala's beaked whales. In February 2021, a pod of three whales was sighted at the Parengarenga Canyons, off North Cape, New Zealand.

In June 2024, scientists aboard Research Storm, a research vessel, detected a pair of juvenile beaked whales off the coast of Baja California. A skin sample taken from the pair later confirmed this as the first known at-sea sighting of this species of beaked whale.

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. 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.

Conservation

The only observations of this species while alive have come 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 pelagic longline 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).

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.

Specimens

• In June 2024 in Baja California found 2 specimens by tracking previously unidentified whale song BW43.

See also

• List of cetaceans

References

• Template:Cite iucn Database entry includes a brief justification of why this species is of data deficient.
• Encyclopedia of Marine Mammals. Edited by William F. Perrin, Bernd Wursig, and J.G.M Thewissen. Academic Press, 2002. Template:ISBN
• 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. Template:ISBN

External links

• Cetaceans of the World
• CMS
• Whale & Dolphin Conservation Society (WDCS)