Indopacetus pacificus

The tropical bottlenose whale (Indopacetus pacificus), also known as the Indo-Pacific beaked whale and 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. 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, in 1882, provided the basis for the initial description of this species by H. A. Longman in 1926. Other researchers were not convinced, and felt this specimen might instead represent a Pacific form of True's beaked whale or a female bottlenose whale. Almost 30 years after Longman's original publication, a second skull was discovered near Danane, Somalia (1955). This specimen likely stranded on the coast, but was subsequently processed into fertilizer. Only the skull survived. Biologist Joseph C. Moore used this skull, together with the original Mackay specimen, to effectively demonstrate that Longman's beaked whale was a unique species and elevated it to its own genus, Indopacetus. Dalebout et al. (2003) used a combination of genetic and morphological analyses to identify four further specimens, including a complete adult female with a fetus found in the Maldives in January 2000. The other remains consisted of a skull from Kenya collected some time before 1968, and two juvenile males from South Africa from strandings in 1976 and 1992. Based on morphological analyses, Dalebout et al. concluded that the genus Indopacetus was a valid one. The external appearance and colour pattern of this species 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. While this paper was in press, a specimen that was first misidentified as a Baird's beaked whale washed up in Kagoshima, Japan, in July 2002. 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 6 m (20 ft) in length, with a 1-m (3-ft) fetus, and the Japanese female was 6.5 m (22 ft) in length. Reports of tropical beaked whales put them even longer, in the 7– to 9-m (23– to 29.5-ft) range, which is larger than any mesoplodont and more typical of a bottlenose whale. No weight estimation or reproductive information is known. Strandings and sightings 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 including the Gulf of Aden 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). Sightings in the Gulf of Mexico are possible, 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. One whale was observed from a whale-watching vessel off Choshi in December, 2015. Possible sightings were made off Tokara Islands and Bonin Islands, as well. They have also recorded off New Caledonia. The range of Longman's beaked whales was once considered to be restricted to warmer waters of Pacific, but stranding records in recent years revealed they may migrate further north to sub-Arctic regions such as off Hokkaido. No occurrence has been confirmed in the Sea of Japan, but a possible Longman's beaked whale stranded on a beach near Vladivostok in 2011.