Tropical bottlenose whale

Tropical bottlenose whale
Conservation status
Data Deficient (IUCN 3.1)[1]
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. 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,^[2] 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 Danae, 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^[3] 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 sighted in the Indian and Pacific Oceans. 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.

Physical 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.

Sperm whale and bottlenose whale

Population and distribution

Carcasses indicate the species ranges across the Indian Ocean from southern and western Africa to the Maldives, 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 the western shore of Mexico. They have also been seen in the Gulf of Mexico, which would indicate they are present in the tropical Atlantic Ocean as well. The most frequent observations have occurred off the coasts of Hawaii. While no specimens have washed up on Hawaii, they are apparently rather common; a 2002 survey estimated 766 animals. No other population estimates exist for other locales.

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".^[4]

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 frequently associated with other species, such as short-finned pilot whales and bottlenose dolphins. Tropical bottlenose whales have been known to breach the surface, and they normally have visible, but short, blows. Their dives have been clocked at 18 to 25 minutes.

Conservation

There are no records of the whale being hunted, caught in fishing gear, or affected by navy sonar. Due to their rather uncommon nature, their conservation status is unknown.

Sources

Cetaceans portal

• 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, pps 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 pps 1-19.
• Relationships among the living genera of beaked whales with classifications, diagnoses and keys J.C. Moore 1968. Field Zoology. Vol 53, pps 206-298.

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. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of data deficient.
2. ^ 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. 
3. ^ Biology.dal.ca
4. ^ HICEAS 2010: Weekly Blog from NOAA Ship McArthur II

External links

• Rare whale washes up in South Africa
• On an unidentified beaked whale found stranded in Kagoshima
• Whale & Dolphin Conservation Society (WDCS)