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Overview

Brief Summary

Description

Almost nothing is known of the ginkgo-toothed beaked whale. Nothing about its behavior or feeding habits has been reported, and its geographical distribution is estimated from a very small sample. Most records are from  Asian waters, where a few were harpooned in fisheries. As with other beaked whales, adult males can be identified by their distinctively-shaped teeth, which are different in each species, but females and juveniles are almost impossible to identify by species.

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Mammal Species of the World
  • Original description: Nishiwaki and Kamiya, 1958.  Sci. Rep. Whales Res. Inst. (Tokyo), 13:53, 13 figs., 17 pls.
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Distribution

Range Description

The ginkgo-toothed beaked whale is known from only a few dozen widely-scattered strandings and captures (no confirmed sightings) in temperate and tropical waters of the Indo-Pacific Ocean, from Sri Lanka east to the shores of North America (California) and the Galápagos Islands (Mead 1989; Pitman 2002). There have been a few records from New Zealand and Australia, indicating that this species also inhabits the southern Indo-Pacific. Most records are from the seas around Japan. Sightings of what may have been this species were also made in the Arabian Sea. It is generally hypothesized that the range is continuous across the Pacific and at least to the eastern Indian Ocean, but until the species can be reliably identified at sea, its true distribution will probably remain unknown (MacLeod et al. 2006).
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Geographic Range

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 )

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Stranding distribution

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.

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Physical Description

Morphology

Physical Description

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

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Tooth morphology

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.

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Skull morphology

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.

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External morphology

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.

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Size

Size in North America

Length:
Range: up to 4.8 m males; up to 4.9 m females

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Ecology

Habitat

temperate to tropical water, oceanic
  • UNESCO-IOC Register of Marine Organisms
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Habitat and Ecology

Habitat and Ecology
Ginkgo-toothed whales are found in the tropical and warm temperate waters of the Indo-Pacific. Like other species in the genus, ginkgo-toothed beaked whales are thought to occur primarily in deep, offshore waters.

These whales are presumed to be primarily squid eaters but may also take some fish.

Systems
  • Marine
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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

  • Moore, J. 1963. Recognizing certain species of beaked whales of the Pacific Ocean. AMER MIDLAND NAT, 70: 396-428.
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Trophic Strategy

Food Habits

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 )

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Associations

Ecosystem Roles

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:

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Predation

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

Known Predators:

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Life History and Behavior

Behavior

Communication and Perception

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 ; acoustic ; echolocation

  • Baumann-Pickering, S., S. Wiggins, E. Roth, M. Roch, H. Schnitzler, J. Hildebrand. 2010. Echolocation signals of a beaked whale at Palmyra Atoll. The Journal of the Acoustical Society of America, 127: 3790-3799.
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Life Expectancy

Lifespan/Longevity

No information is available.

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Reproduction

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); 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)

  • Nishiwaki, M., T. Kasuya, K. Kureha, N. Oguro. 1972. FURTHER COMMENTS ON MESOPLODON-GINKGODENS. Scientific Reports of the Whales Research Institute Tokyo, 24: 43-56.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.

Reviewer/s
Hammond, P.S. & Perrin, W.F. (Cetacean Red List Authority)

Contributor/s

Justification
There is no information on abundance or trends in global abundance for this species. As a relatively uncommon species it is potentially vulnerable to low-level threats and a 30% global reduction over three generations cannot be ruled out (criterion A).

History
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
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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

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Population

Population
There are no estimates of abundance, but the species does not appear to be very common anywhere. There is no information on trends in the global abundance of this species.

Population Trend
Unknown
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Threats

Major Threats
Ginkgo-toothed beaked whales have occasionally been taken by Japanese and Taiwanese whalers, and some have been caught in deepwater drift gillnets.

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006). The use of active sonar from military vessels has been implicated in mass strandings of ginkgo-toothed beaked whales (Wang and Yang 2006; Yang et al. 2008).

Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.

Predicted impacts of global climate change on the marine environment may affect this species of whale, although the nature of impacts is unclear (Learmonth et al. 2006).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES. Research is needed to determine the impacts of potential threatening processes on this species.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

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

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Economic Importance for Humans: Positive

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

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Risks

IUCN Red List Category

Data Deficient (DD)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Ginkgo-toothed beaked whale

Ginkgo-toothed beaked whale!<-- This template has to be "warmed up" before it can be used, for some reason -->

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.

Contents

Physical appearance

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 ginko 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 moderately long length. The coloration is overall dark gray on males with light patches on the front half of the beak and around the head, and also have small white spots on the bottom of the tail, but the location may be variable. Females are a lighter gray and have countershading. Both of the genders reach 4.9 meters (16 feet) in length. They are around 2.4 meters long (8 feet) when born. The largest sizes for male and female are the following: Male: 4.8 meters Female: 4.9 meters

The size of these whales at birth are about 2 meters.

[1] [2] [3] [4] [5]

Population and distribution

This beaked whale has had less than 20 strandings off the coasts of Japan, 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 is no way to judge the population.

Behavior

The males probably do not engage in combat and the species probably feed on squid and fish. No other information is known.

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.

Specimens

References

  1. ^ www.environment.gov.au/
  2. ^ www.austmus.gov.au/
  3. ^ www.nlbif.eti.uva.nl
  4. ^ www.abssoluteastronomy.com
  5. ^ www.cms.int
  • Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. (2008). Mesoplodon ginkgodens. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. 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. ISBN 0-12-551340-2
  • 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. ISBN 0-7136-6334-0
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