Mesoplodon ginkgodens, Nishiwaki & Kamiya, 1958

Russell A. Mittermeier & Don E. Wilson, 2014, Ziphiidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 326-357 : 355

16.

Ginkgo-toothed Beaked Whale

Mesoplodon ginkgodens

French: Baleine-a-bec du Japon / German: Japan-Zweizahnwal / Spanish: Zifio de dientes de Ginkgo

Other common names: Japanese Beaked Whale

Taxonomy. Mesoplodon ginkgodens Nishiwaki & Kamiya, 1958 ,

Japan, “Oiso Beach, Sagami Bay, near Tokyo.”

Historically, there has been confusion about the number ofspecies or subspecies contained in the classification of M. ginkgodens . It was originaly described in 1958 from an animal which stranded in Japan, while a second similar species, M. hotaula , was described independently in 1963 from an animal which stranded in Sri Lanka. Based on morphological similarities, these two species were synonymized under the name M. ginkgodens by J. C. Moore and R. M. Gilmore in 1965. However, recent molecular analysis, published in 2014, has resulted in these two species being separated again. Monotypic.

Distribution. Warmer waters ofthe Pacific and Indian oceans in an area ranging from S India and Sri Lanka to Taiwan, Japan, SE Australia, Galapagos Is, and California. Exact distribution remains unclear due to the small number of known strandings, and the taxonomic confusion between the Ginkgo-toothed Beaked Whale and the Deraniyagala’s Beaked Whale (Mesoplodonhotaula).

Descriptive notes. Total length 470-528 cm; weight ¢.1000 kg (unconfirmed). Body of the Ginkgo-toothed Beaked Whale is spindle-shaped, with greatest girth around its midpoint. Flukes are wide in relation to body length, and tailstock is compressed laterally. Dorsal fin is small and set approximately two-thirds the distance between tip of the beak and end ofthe tail. Coloration is typically dark brown, dark gray, or black. Female and juvenile Ginkgo-toothed Beaked Whales may be paler on ventral surface. Rostrum and lower jaw form a beak that is indistinct from the low sloping forehead. There are two grooves on the throat. Adult males have a single tusk on each side of the lower jaw. Tusks are positioned approximately one-third of the way along the mandibles, but only the very tips of tusks emerge from gums. Male Ginkgo-toothed Beaked Whales are unusual because they seem to lack any of the long, pale, linear scars caused by tusks of other males that are found on males of most species of beaked whales.

Habitat. Primarily waters greater than 200 m deep. Nothing further is known about habitat preferences of Ginkgo-toothed Beaked Whales.

Food and Feeding. There is no specific information available for this species, but in common with other species of beaked whales, Ginkgo-toothed Beaked Whales are thought to consume deep-water squid and, to a lesser extent, deep-water fish. They likely forage at depths greater than 500 m.

Breeding. There is no information available for this species.

Activity patterns. There is no information available for this species.

Movements, Home range and Social organization. There is no specific information available for this species, but Ginkgo-toothed Beaked Whales likely occur in small groups.

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The IUCN RedList. There are no estimates of global population size of the Ginkgo-toothed Beaked Whale. Like other species of beaked whales, the Ginkgo-toothed Beaked Whale is potentially affected by ingestion of plastic debris and noise pollution, and individuals can be killed as bycatch in driftnet fisheries. Nevertheless, nothing is known about the form or extent of these potential impacts.

Bibliography. Dalebout et al. (2014), MacLeod et al. (2006), Mead (1989b), Moore & Gilmore (1965), Rice (1998).

Figures

On following pages: 18. Sowery's Beaked Whale (Mesoplodon bidens); 19. Blainville’s Beaked Whale (Mesoplodon densirostris); 20. Andrews's Beaked Whale (Mesoplodon bowdoini); 21. Spade-toothed Whale (Mesoplodon traversil); 22. Gervais's Beaked Whale (Mesoplodon europaeus).

Distribution. Warmer waters ofthe Pacific and Indian oceans in an area ranging from S India and Sri Lanka to Taiwan, Japan, SE Australia, Galapagos Is, and California. Exact distribution remains unclear due to the small number of known strandings, and the taxonomic confusion between the Ginkgo-toothed Beaked Whale and the Deraniyagala’s Beaked Whale (Mesoplodonhotaula).