Ginkgo-toothed beaked whale (Mesoplodon ginkgodens)

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Ginkgo-toothed beaked whale fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Ginkgo-toothed beaked whale description

The elusive ginkgo-toothed beaked whale (Mesoplodon ginkgodens) is only known from widely scattered strandings or captures ⁽¹⁾. Males of this species are dark grey to black with lighter spots, while females are lighter in colour ⁽⁵⁾ and may have slightly paler heads ⁽⁴⁾.

Just behind the middle of the lower jaw, on a slightly raised area, mature adult males have flattened tusks that only just protrude through the gum line. These erupted teeth are not present in female or juvenile ginkgo-toothed beaked whales, and are thought to be used by males for fighting ^{(3) (4) (5)}. The ginkgo-toothed beaked whale is named for the shape of the male’s teeth, which resemble the leaf of a ginkgo tree ⁽⁴⁾.

In comparison with other beaked whales in the genus Mesoplodon, the adult male ginkgo-toothed beaked whale appears to be less heavily scarred ^{(3) (4) (5)}, possibly as the teeth are only barely exposed above the gums so cause less damage to opponents during fights ⁽³⁾. Both sexes may also bear small, oval scars from the bites of cookie-cutter sharks (Isistius species) ⁽⁷⁾.

The ginkgo-toothed beaked whale has a small, triangular dorsal fin situated towards the rear of the body, and a small, low, inconspicuous blow hole towards the front ^{(4) (5) (7)}. As in other Mesoplodon species, the body is spindle-shaped, the flippers are small and narrow, and the tail fin lacks a notch in the middle. The ginkgo-toothed beaked whale’s head is small and tapered, and there is a pair of external grooves on the underside of the throat ^{(4) (7)}.

Also known as

ginkgo beaked whale, ginkgo-toothed whale, Japanese beaked whale.

Synonyms

Mesoplodon hotaula.

French

Mésoplodon De Nishiwaki.

Spanish

Zifio De Nishiwaki.

Size

Length: up to 5 m ^{(2) (3) (4)}

Length at birth: 2 - 2.5 m ⁽⁵⁾

Weight

c. 1.5 tonnes ^{(2) (3) (4)}

Ginkgo-toothed beaked whale biology

The ginkgo-toothed beaked whale is almost impossible to identify at sea, and as yet there have been no confirmed live sightings of this poorly known species. As a result, very little is currently known about its biology and behaviour ^{(4) (5) (8)}.

As in other beaked whales, the diet of the ginkgo-toothed beaked whale is likely to be primarily composed of squid, although it may also predate fish ^{(1) (2) (3) (7)}. This whale is thought to be a suction feeder, sucking in squid or fish and swallowing them whole. The pair of grooves on the throat may allow the mouth floor to distend, helping the whale to suck in and swallow larger prey ^{(3) (7)}.

In general, Mesoplodon species are quite slow and sluggish in their movements, and do not spend much time at the water’s surface ⁽⁵⁾. However, these species are believed to actively pursue their prey, and are thought to be capable of deep dives ^{(3) (5)}.

It is thought that pods of Mesoplodon species usually consist of up to seven individuals ⁽⁵⁾. Maturity is likely to be reached when the ginkgo-toothed beaked whale attains a length of around 4.5 metres ^{(2) (3)}, and the characteristic teeth of beaked whales are suggested to be used by males in fights to establish breeding hierarchies ^{(3) (7)}.

Ginkgo-toothed beaked whale range

This species is believed to occur in parts of the Pacific and eastern Indian Oceans. It is thought to most commonly occur in the western North Pacific, with most records from the seas around Japan, although stranding records suggest that the ginkgo-toothed beaked whale ranges from Sri Lanka to the eastern shores of North America and the Galapagos Islands ^{(1) (2) (8)}.

Records from New Zealand and Australia also indicate that the range of the ginkgo-toothed beaked whale encompasses the southern Indo-Pacific Ocean ^{(1) (2) (3) (8)}, and possible sightings of this species have been reported in the Arabian Sea ^{(1) (7)}.

Ginkgo-toothed beaked whale habitat

Similarly to other beaked whales, the ginkgo-toothed beaked whale inhabits deep offshore waters. This whale occurs in the tropical and warm temperate waters of the Indo-Pacific Ocean ^{(1) (2) (3)}.

Ginkgo-toothed beaked whale status

The ginkgo-toothed beaked whale is classified as Data Deficient (DD) on the IUCN Red List ⁽¹⁾ and is listed on Appendix II of CITES ⁽⁶⁾.

Ginkgo-toothed beaked whale threats

Japanese and Taiwanese whalers occasionally catch ginkgo-toothed beaked whales, and this species may also be caught accidentally in deep-water drift gillnets ^{(1) (2) (3)}. Additionally, man-made noise pollution, such as seismic exploration and navy sonar, has been indicated as a threat to the ginkgo-toothed beaked whale, potentially causing mass strandings of this species ⁽¹⁾. Competition for squid stocks from expanding commercial fisheries may also become a threat to these whales in the future ^{(2) (3)}.

Other potential risks to the ginkgo-toothed beaked whale include pollution, swallowing plastic items, and the predicted changes to the whale’s marine environment as a result of global climate change ^{(1) (2) (3)}. Information on the global abundance and population trends for this species is very limited, so cannot currently be used to assess its conservation status ⁽¹⁾.

Ginkgo-toothed beaked whale conservation

The ginkgo-toothed beaked whale is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade in this species should be carefully controlled ⁽⁶⁾.

Although there are not yet any specific efforts being made to conserve this species, there are efforts to conserve some of its habitats. For example, the Australian Exclusive Economic Zone is a protected area of 200 nautical miles around Australia, which encompasses parts of the ginkgo-toothed beaked whale’s range. In addition, the Indian Ocean Sanctuary and the Southern Ocean Sanctuary are covered by International Whaling Commission regulations, further protecting a portion of this species’ habitat ^{(2) (3)}.

Further research is needed to assess the impacts of the potential threats to the ginkgo-toothed beaked whale ⁽¹⁾. The Action Plan for Australian Cetaceans lists a number of conservation actions for the ginkgo-toothed beaked whale around Australia, including assessing the impact of pollutants, establishing an abundance index, and further increasing knowledge of this species. Increased international efforts are also needed to reduce the threats to the ginkgo-toothed beaked whale, and the development of squid fisheries needs to be monitored ⁽³⁾.

As so little is currently known about this rarely seen whale, further materials are needed to help identify it and other Mesoplodon species at sea, and as much information as possible needs to be gained from any individuals that strand ⁽³⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

Find out more about the ginkgo-toothed beaked whale:

• Convention on Migratory Species - Mesoplodon ginkgodens:
  http://www.cms.int/reports/small_cetaceans/data/m_ginkgodens/m_ginkgodens.htm

More information on beaked whales and their conservation:

• The Beaked Whale Resource:
  http://www.beakedwhaleresource.com/index.html
• Whale and Dolphin Conservation Society:
  http://www.wdcs.org/

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Glossary

Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

References

1. IUCN Red List (September, 2012)
   http://www.iucnredlist.org/
2. Ross, G.J.B. (2006) Review of the Conservation Status of Australia’s Smaller Whales and Dolphins. Australian Government, Canberra. Available at:
   http://www.environment.gov.au/coasts/publications/pubs/conservation-smaller-whales-dolphins.pdf
3. Bannister, J.L., Kemper, C.M. and Warneke, R.M. (1996) The Action Plan for Australian Cetaceans. Australian Nature Conservation Agency, Canberra. Available at:
   http://www.environment.gov.au/coasts/publications/cetaceans-action-plan/pubs/whaleplan.pdf
4. Leatherwood, S., Reeves, R.R., Perrin, W.F. and Evans, W.E. (1988) Whales, Dolphins, and Porpoises of the Eastern North Pacific and Adjacent Arctic Waters: A Guide to their Identification. Dover Publications, Mineola, New York.
5. Jefferson, T.A., Leatherwood, S. and Webber, M.A. (1993) FAO Species Identification Guide. Marine Mammals of the World. FAO, Rome. Available at:
   ftp://ftp.fao.org/docrep/fao/009/t0725e/t0725e00.pdf
6. CITES (September, 2012)
   http://www.cites.org/
7. Pitman, R. (2002) Mesoplodont whales. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds.) Encyclopedia of Marine Mammals. Academic Press, San Diego, California.
8. MacLeod, C.D., et al. (2006) Known and inferred distributions of beaked whale species (Cetacea: Ziphiidae). Journal of Cetacean Research and Management, 7(3): 271-286.