Tropical bottlenose whale

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Tropical bottlenose whale
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Ziphiidae
Subfamily: Hyperoodontinae
Genus: Indopacetus
Binomial name
Indopacetus pacificus
Longman, 1926
Tropical Bottlenose Whale range
Synonyms

Mesoplodon pacificus

The tropical bottlenose whale (Indopacetus pacificus), also known as the Indo-Pacific beaked whale and the Longman's beaked whale, was considered to be the world's rarest cetacean until recently, but the spade-toothed whale now holds that position. As of 2010, the species is now known from nearly a dozen strandings and over 65 sightings.[2]

History of discovery

The species has had a long history riddled with misidentifications, which are now mostly resolved. A skull and jaw found on a beach in Mackay, Queensland, Australia in 1882 provided the initial description by H. A. Longman in 1926,[3] but some authorities insisted on classifying it as a True's beaked whale or a female bottlenose whale instead of a new species. A whale washed up near Danane, Somalia in 1955 was processed into fertilizer with only the skull remaining, and biologist Joseph C. Moore used it to effectively demonstrate it was a unique species. However, there was a considerable debate as to whether the whale belonged in the genus Mesoplodon or not.

The next major development happened when a paper[4] had shown there were actually six remains of the whale, including a complete female with a fetus found in the Maldives in 2000. The other remains consisted of a skull from Kenya from before 1968, and two juveniles from South Africa in 1976 and 1992, respectively. The paper used DNA analysis to show the tropical bottlenose whale is likely to be an independent genus, but information on other species was too lacking to establish any concrete phylogeny. The external physical appearance was also revealed, and a firm connection was established with the mysterious tropical bottlenose whales that had been sighted in the Indian and Pacific Oceans since the 1960s. During the publication of the paper, a specimen originally identified as a giant beaked whale washed up in Kagoshima, Japan in July 2002. Another specimen claimed to be a tropical bottlenose whale, which washed up in South Africa in August 2002, is likely a misidentified Cuvier's beaked whale.

Description

The Longman's beaked whales look rather similar to both mesoplodont beaked whales and bottlenose whales, which led to a great deal of taxonomic confusion. The Maldives female had a robust body like the bottlenoses, although this may be a distortion, since the less-decomposed female specimen from Japan had a laterally compressed body typical of Mesoplodon. The juvenile specimens have a very short beak similar to a bottlenose whale, but the adult females seen so far have had rather long beaks sloping gently into a barely noticeable melon organ. Additionally, the dorsal fins of adult specimens seem unusually large and triangular for beaked whales, whereas in juveniles they are rather small and swept back.

An adult male specimen has yet to wash up, but sightings of the tropical bottlenose whale indicate they have a rather bulbous melon, two teeth located towards the front of the beak, and scars from fighting with the teeth. Scars from cookiecutter sharks are also rather common on the whale. The rather unusual coloration of the juveniles helped connect the Longman's to the tropical bottlenose whale; both have dark backs behind the blowholes, which quickly shade down to a light gray and then white. The blackness from the back extends down to the eye of the whale except for a light spot behind the eye, and then continues on in a line towards the flipper, which is also dark.

Dark markings are also present on the tip of the beak and rostrum. The females have a simpler coloration; the body is typically grayish except for a brown head. The coloration appears to be rather variable in this species. The female specimen from the Maldives was six metres (20 feet) in length, with a one-metre (3 foot) fetus, and the Japanese female was 6.5 metres (22 feet) in length. Reports of tropical beaked whales put them even longer, in the 7–8 metre (23–26 foot) range, which is larger than any mesoplodont and more typical of a bottlenose whale. No weight estimation or reproductive information is known.

On November 16, 2013, 8 whales identified as Longman's Beak Whales entered Somme Bay south of New Caledonia, a French Overseas Territory in Southwest Pacific Ocean. It was the first known encounter of this whale in New-Caledonia. On Monday 18th, 2 alive specimen were still inside the bay while 4 were found dead. Three of the dead whales were buried at Mont-Dore community waiting for further scientific investigations.[5]

Population and distribution

Strandings indicate the species ranges across the Indian Ocean from southern and eastern Africa to the Maldives, Sri Lanka, and east to Myanmar with a Pacific range extending from Australia to Japan. However, if the sightings of tropical beaked whales are taken into account, the range of this whale is more extensive; they have been sighted from the Arabian Sea to Guadalupe Island and the Gulf of California (the sightings off Mexico (in 1992 and 1993) are probably extralimital, as they are associated with abnormally warm water during El Niño events). There have also been possible sightings in the Gulf of Mexico, which may indicate they are present in the tropical Atlantic Ocean as well. The most frequent observations have occurred off the coasts of Hawaii. Although only a single specimen has washed up in Hawaii, they are apparently rather common; a 2002 survey estimated 766 animals. No other population estimates exist for other locales although a single individual was apparently identified in the Comoro Islands in the summer of 2002-2003.[6]

In 2009, the first confirmed sighting was made of tropical bottlenose whales in the southern Bay of Bengal.[7] In the summer and fall of 2010, researchers aboard the NOAA ship McArthur II made two sightings of groups of tropical bottlenose whales off Hawaii. The first sighting consisted of a "large, active group" of over 70 individuals surfacing rapidly and breaching on occasion; the second sighting, late in October, did not last as long, as the group "ran away".[8]

Since Dalebout et al. (2003), additional strandings have been reported in the Philippines (2004), Taiwan and Myanmar (2005),[9] the Andaman Islands (2009), and Maui (2010).[10]

Behavior

Tropical bottlenose whale observations indicate they travel in larger groups than any other local species of beaked whales. The size of the pods range from the tens up to 100, with 15 to 20 being fairly typical, and the groups appear very cohesive. Their pods are sometimes associated with other species, such as short-finned pilot whales, bottlenose dolphins, and spinner dolphins. Tropical bottlenose whales have been known to breach the surface, and they normally have visible, but short, blows. Their dives last between 11 and 33 minutes, with one individual diving for least 45 minutes.[11]

Conservation

There are no records of the whale being hunted, although individuals have been trapped in fishing nets off Sri Lanka and a stranding in Taiwan in 2005 involving a cow-calf pair may have been due to nearby naval exercises.[12] Due to their rather uncommon nature, their conservation status is unknown. The tropical bottlenose whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[13]

References

  1. ↑ 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). Indopacetus pacificus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 24 March 2009. Database entry includes a brief justification of why this species is of data deficient.
  2. ↑ Pitman, R. L. (2009). "Indo-Pacific beaked whale – Indopacetus pacificus". In Perrin, W. F.; Würsig, B.; Thewissen, J. G. M. Encyclopedia of Marine Mammals (2nd ed.). Amsterdam: Academic Press. pp. 600–602. ISBN 9780123735539. 
  3. ↑ Reeves, R., Stewart, B., Clapham, P. & Powell, J. (2002). Guide to Marine Mammals of the World. New York: A.A. Knopf. p. 266. ISBN 0-375-41141-0. 
  4. ↑ Biology.dal.ca
  5. ↑
  6. ↑ Kiszka, J., O. Breysse, M. Vely, and K. Boinali. 2006. Marine mammals around the Comoros archipelago (Mozambique Channel): recent records and review of available information. Scientific Committee Report to the International Whaling Commission. SC-58-O6
  7. ↑ Afsal, V.V, P. P. Manojkumar, K.S.S.M. Yousuf, B. Anoop and E. Vivekanandan (2009). The first sighting of Longman’s beaked whale, Indopacetus pacificus, in the southern Bay of Bengal. Marine Biodiversity Records, pp. 1-3.
  8. ↑ HICEAS 2010: Weekly Blog from NOAA Ship McArthur II
  9. ↑ Indopacetus pacificus stranding at the Yangon River mouth, July 2005
  10. ↑ Indopacetus pacificus specimens - Natural Museum of Natural History Collections
  11. ↑ Anderson, R. C.; Clark, R.; Madsen, P. T.; Johnson, C.; Kiszka, J.; Breysse, O. (2006). "Observations of Longman's Beaked Whale (Indopacetus pacificus) in the Western Indian Ocean". Aq. Mamm. 32 (2): 223–231. doi:10.1578/AM.32.2.2006.223. 
  12. ↑ Yang WC, Chou LS, Jepson PD, Brownell RL Jr, Cowan D, Chang PH, Chiou HI, Yao CJ, Yamada TK, Chiu JT, Wang PJ, Fernández A.(2008). Unusual cetacean mortality event in Taiwan, possibly linked to naval activities. Vet. Rec. 162:184-6.
  13. ↑ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region

Further reading

  • Longman's Beaked Whale Hawaiian Stock. Revised 3/15/05. Available: here
  • Appearance, Distribution, and Genetic Distinctiveness of Longman's Beaked Whale, Indopacetus pacificus. Dalebout, Ross, Baker, Anderson, Best, Cockcroft, Hinsz, Peddemors, and Pitman. July 2003, Marine Mammal Science, 19(3):421–461. Available: here
  • National Audubon Society Guide to Marine Mammals of the World Reeves et al., 2002. ISBN 0-375-41141-0.
  • Sightings and possible identification of a bottlenose whale in the tropical Indo-Pacific: Indopacetus pacificus? Pitman, Palacios, Brennan, Brennan, Balcomb and Miyashita, 1999. Marine Mammology Science Vol 15, pp 531–549.
  • Encyclopedia of Marine Mammals Robert L. Pitman, 1998. ISBN 0-12-551340-2
  • Whales, Dolphins and Porpoises Carwardine, 1995. ISBN 0-7513-2781-6
  • More skull characters of the beaked whale Indopacetus pacificus and comparative measurements of austral relatives J.C. Moore 1972. Field Zoology. Vol 62 pp 1–19.
  • Relationships among the living genera of beaked whales with classifications, diagnoses and keys J.C. Moore 1968. Field Zoology. Vol 53, pp 206–298.

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