Ginkgo Toothed Beaked Whale

Photographs of distinctive bite marks on Mesoplodon ginkgodens indicate that their main predators may be sharks, especially cookiecutter sharks.

Known Predators:

• Cookiecutter shark Isistius brasiliensis

Although there is no information ragarding communication and perception in Mesoplodon ginkgodens, studies of echolocation in numerous other Mesoplodon show that they use echolocation to navigate and find prey. It is likely that frequency-modulated pulses differ by species. Pulses probably vary according to the nature of activities being conducted.

Communication Channels: acoustic

Perception Channels: visual ; tactile ; acoustic ; echolocation ; chemical

Because there are so few wild encounters with Mesoplodon ginkgodens, it is difficult to determine population trends to assess potential conservation needs. This species is listed as "data deficient" on the IUCN's Red List of Threatened Species, and is listed under Appendix II on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Mesoplodon ginkgodens is not considered as part of the United States Endangered Species Act.

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: data deficient

There are no known adverse effects of Mesoplodon ginkgodens on humans.

There are no known positive effects of Mesoplodon ginkgodens on humans.

Mesoplodon ginkgodens feed on primarily squid and fish and in doing so, likely influence the populations of these animals. In addition, Mesoplodon ginkgodens serve as host to ocean parasites such as the lampreys.

Commensal/Parasitic Species:

• Lampetra tridentata

Based on findings of similar species and on the nature of their teeth, Mesoplodon ginkgodens probably feeds on squid and fish. Some species specialize on one prey more than the other, but the feeding habits of M. ginkgodens are unknown. In addition to fish and squid, a small amount of crustaceans have been found in the stomachs of other Mesoplodon species.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore , Molluscivore )

Ginkgo-toothed beaked whales (Mesoplodon ginkgodens) reside in tropical and temperate waters throughout the Pacific and Indian Oceans. The range of this species is known from 16 specimens that were found stranded on the coasts of Japan, Taiwan, Sri Lanka, Indonesia, Australia, Southwest California, Mexico and Ecuador. There have been no confirmed sightings of live species in open oceans; however, it is presumed that they are found in the Indian and Pacific Oceans from southern California to the southern tip of India.

Biogeographic Regions: indian ocean (Native ); pacific ocean (Native )

No habitat information is available for Mesoplodon ginkgodens. The habits of close relatives, Mesoplodon densirostris and Mesoplodon peruvianus, suggest that M. ginkodens prefers slightly cooler areas within the temperate/tropical zone and also upwelling regions. Upwelling regions are highly productive due to nutrient-rich bottom waters cycling to the surface.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic

No information is available.

Based on stranded specimens, adult males appear to be mainly dark grey, darker dorsally and slightly paler ventrally. The rostrum and lower jaw of Mesoplodon ginkgodens both have a small pale gray patch. Adult females are generally paler than males. Adults of both genders display white spots and small blade-like scars. White spots are found towards the posterior end of the ventral surface and are believed to be either from natural pigmentation or parasitism. Mesoplodon ginkgodens has a pair of distinguishing ginkgo-shaped teeth, one on each side of the lower jaw towards the middle of the beak. In males they erupt beyond the gum line, but in females they do not. This characteristic tooth is present in all males in the Mesoplodon genus. Mesoplodon ginkodens is distinguished from other Mesoplodon by the great width of its ginko-shaped tooth, which is always >100mm. Males and females reach a maximum of 5.3 meters.

Range length: 5.3 (high) m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes colored or patterned differently

There is no information available regarding the mating system of Mesoplodon ginkgodens.

There is no information available regarding the general reproductive behavior of Mesoplodon ginkgodens.

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

While no parental investment information specific to << Mesoplodon ginkgodens>> is available, as mammals, it can be assumed that females likely provide their young with milk and protection until weaning.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female); pre-independence (Provisioning: Female)

Diagnostic features of the skull and mandible On the vertex of the dorsal skull the premaxillary bone extends forward of the nasal and frontal bones. Separates from Berardius and Ziphius. A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their combined middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus. When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon. Tooth alveoli of mandible are posterior to the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. bidens, M. bowdoini, M. carlhubbsi, M. europaeus, M. grayi, M. hectori, M. layardii, M. mirus, M. perrini, and M. traversii, Right premaxilla does not extend posteriorly beyond the right nasal or extends 5mm or less beyond right nasal. Separates from M. densirostris, M. peruvianus, and M. stejnegeri.

Diagnostic features of the skull and mandible On the vertex of the dorsal skull the premaxillary bone extends forward of the nasal and frontal bones. Separates from Berardius and Ziphius. A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their combined middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus. When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon. Tooth alveoli of mandible are posterior to the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. bidens, M. bowdoini, M. carlhubbsi, M. europaeus, M. grayi, M. hectori, M. layardii, M. mirus, M. perrini, and M. traversii, Right premaxilla does not extend posteriorly beyond the right nasal or extends 5mm or less beyond right nasal. Separates from M. densirostris, M. peruvianus, and M. stejnegeri.

Stranding Distribution This species is known primarily from the North Pacific although it occurs in the South Pacific and Indian oceans. It is a relatively little known species, but seems to prefer warm temperate to tropical waters between 40o N and 40o S.

Tooth position A single pair of teeth are positioned at the top of the anterior edge of the jaw arch. The tooth root is squared at the base. Tooth exposure Erupted teeth in adult males are covered by gum tissue with only the tip of tooth exposed. Teeth do not erupt in females or juveniles. Tooth shape The teeth resemble the leaf of a ginkgo tree. The denticle is centrally positioned between anterior and posterior most points of the tooth. Anterior and posterior tooth margins are concave and nearly symmetric.

Adult male ginkgotoothed beaked whales are dark grey, with light spots; females are apparently lighter. They do not appear to be as heavily scarred as most other mesoplodonts. The throat grooves, dorsal fin, and tail flukes are typical for Mesoplodon species. Bulls have flattened tusks that barely break the gumline, slightly behind the middle of the lower jaw; erupted teeth are absent in females. Can be confused with: The uniform dark pigmentation, small posteriorly placed teeth, and paucity of characteristic ziphiid scars may allow a tentative classification of adult male ginkgo-toothed beaked whales. Otherwise, this species will be virtually indistinguishable from other species of Mesoplodon.

Maximum known sizes are 4.9 m (females) and 4.8 m (males). At birth, they are thought to be about 2 to 2.5 m.

Almost nothing is known of the biology of the ginkgo-toothed beaked whale.

A few animals have been taken in coastal fisheries off Japan. IUCN: Insufficiently known.

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 the males not having any scarring.

temperate to tropical water, oceanic

Data Deficient (DD)