Longman’s beaked whales have somewhat steep, bulging foreheads and tube-like beaks, sometimes with a crease between the melon and beak. As in most other beaked whales, the dorsal fin is located behind the midpoint of the back, but it is larger than in other beaked whales. During at-sea sightings, no teeth have been visible outside the closed mouth. There is generally a pair of V-shaped throat grooves.
Coloration ranges from umber-brown to bluish-gray, generally with light areas on the sides and around the head. Some individuals have had scratches on the back. When seen, the blowhole was oriented with the concavity facing anteriorly; this is the opposite of the situation in Baird's beaked whale, the species with which it is most easily confused in the North Pacific.
There is a single pair of oval teeth at the tip of the lower jaw, which may be embedded in the gums.
This is a relatively large beaked whale; size estimates have been in the range of 4-9 m. A fresh female stranded recently in Japan measured about 6.5 m long.
Can be Confused With
The large size and relatively steep forehead of this species should rule-out confusion with most species of beaked whales. However, the southern bottlenose and Baird’s and Arnoux’s beaked whales may cause some confusion. In shape and position, the teeth most closely resemble those of True’s beaked whale. Examination of the skull by experts or genetic analyses may be required for positive identification.
There have been several sightings at widespread locations in the tropical Pacific and Indian oceans of a beaked whale that is thought to be this species. The distribution of Longman’s beaked whale is incompletely known, but it it is probably limited to the Indo-Pacific region. The available specimens are from Australia, Somalia, South Africa, the Maldives, Kenya, and Japan. The sightings come from scattered locations in the tropical to subtropical Indo-Pacific. These beaked whales are only rarely seen in the eastern tropical Pacific.
Ecology and Behavior
Large, coordinated groups appear to be characteristic of this species. Herds sighted in the Pacific Ocean have contained from 1-100 individuals, with many groups of 10 or greater (this is much larger than for Cuvier’s beaked whale or the various Mesoplodon species).
Essentially all aspects of the biology of Longman’s beaked are very poorly known. The species was only known from two skulls until the last few years.
Feeding and Prey
Nothing is known of its feeding habits, except for the stomach contents of one specimen from Japan. These suggested that the species may feed primarily on cephalopods, like other beaked whales.
Threats and Status
There is no known exploitation of this species. All records are of strandings or sightings. Currently, Longman’s beaked whales are ‘Data Deficient’ (IUCN) and ‘Not Listed’ (ESA).
Dalebout, M. L. 2002. Species identity, genetic diversity, and molecular systematic relationships among the Ziphiidae (beaked whales). Ph.D. dissertation, University of Auckland, New Zealand.
Dalebout, M.L., G.J.B. Ross, C.S. Baker, R.C. Anderson, P.B. Best, V.G. Cockcroft, H.L. Hinsz, V. Peddemors and R.L. Pitman. 2003 Appearance, distribution and genetic distinctiveness of Longman’s beaked whale, Indopacetus pacificus. Marine Mammal Science 19:421-461.
Pitman, R.L. 2002. Indo-Pacific beaked whale Indopacetus pacificus. pp. 615-617 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Pitman, R.L., D.M. Palacios, P.L.R. Brennan, B.J. Brennan, K.C. Balcomb, III, and T. Miyashita. 1999. Sightings and possible identity of a bottlenose whale in the tropical Indo-Pacific Indopacetus pacificus. Marine Mammal Science 15:531-549.
Yamada, T. 2002. On an unidentified beaked whale found stranded in Kagoshima. National Science Museum, Tokyo, Japan. Available online here.