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 found in Mackay, Queensland, Australia provided the initial description, but some authorities insisted on classifying it was 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 that 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, available here, had shown that 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 that 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 Bottlenose Whales, although this may be a distortion since the less decomposed female specimen from Japan had a laterally compressed body typical of Mesoplodonts. 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 that they have a rather bulbous melon, two teeth located towards the front of the beak, as well as the 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 Beaked Whale to the Tropical Bottlenose Whale; both of them have a dark back behind the blowhole which quickly shades 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. It appears that the coloration is rather variable in this species. The female specimen from the Maldives was 6 meters (20 feet) in length with a 1 meter (3 foot) fetus, and the Japanese female was 6.5 meters (22 feet) in length. Reports of Tropical Beaked Whales put them at even larger length in the 7-8 meter (23–26 foot) range, which is larger than any Mesoplodon and more typical of a Bottlenose Whale. No weight estimation or reproductive data is known.

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 up to Japan. However, if the sightings of the Tropical Beaked Whale are taken into account, the range of this whale is extensively larger. 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 that 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 from Hawaii, they are apparently rather common; a 2002 survey estimates that there were 766 animals. No other population estimates exist for other locales.

Behavior

Tropical Bottlenose Whale observations indicate that they travel in larger groups than any other local species of beaked whale. 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