Longman's beaked whale
Longman's beaked whale (scientific name: Indopacetus pacificus) is is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long and narrow beaks and dorsal fins set far back on their bodies. They are marine mammals within the order of cetaceans. It is a very rare whale and, untill recently, only known from the skulls of two specimens.
Size estimates range from four to nine meters based on extrapolation from skull measurements. A Japanese specimen was 6.5 meters in length, which seems about average based on partial skeletal specimens.
Like all beaked whales, this species has a prominent slender beak. Also diagnostic of beaked whales, the throat has two grooves which form a V shape and the fluke is not notched. This whale has a proportionately smaller head than most beaked whales. It is, however, larger overall than most of its close relatives.
Longman’s beaked whales are most morphologically similar to Baird’s beaked whales (Beradius bairdii). They may be distinguished, however, because Longman’s beaked whales have a blow hole with concavity oriented forward, toward the anterior of the whale. In Baird’s whales the blow hole tilts toward the posterior.
The dorsal fin is larger than that of most beaked whales. The lower jaw contains only a pair of oval teeth, which do not protrude from the jaw.
The skin coloration varies between brown and bluish gray and tends to lighten around the flank and head. These whales are sexually dimorphic, with males tending to be larger. Body mass estimates are not readily available as of 2011.
Other Physical Features: endothermic metabolism; bilateral symmetry
Key behaviors are: natatorial; motile; and social. Individuals have been sighted in the Pacific in groups of up to 100 or singly. Groups of greater than ten have been most commonly recorded. (Indopacetus pacificus, 2005)
Pelagic beaked whales use echolocation to locate food. (Johnson et al., 2004) Other perception channels are tactile and chemical. This marine mammal also uses acoustic signaling for communication with other species members.
Key reproductive reatures are: Iteroparous; Gonochoric/gonochoristic/dioecious (sexes separate); Viviparous. Little detailed information is available on species mating and reproduction in Longman's beaked whales. In fact, very little information is known about beaked whale (Ziphiidae) reproduction in general.
Most toothed whales (Odontoceti), the mammalian suborder that includes beaked whales, have a gestation period of ten to twelve months. Lactation may last from 18 to 24 months, or more. Calving generally occurs every two or three years, and some females may become pregnant while still lactating. Males tend to be larger and reach sexual maturity later. (Evans, 1987)
Like all placental mammals (Eutheria), female beaked whales gestate young for an extended period, and protect and nourish them until they reach independence. Some whales travel in family groups and maintain bonds after young have reached independence.
Distribution and Movements
The IUCN Red List note:
There have been many sightings at widespread locations in the tropical Pacific and Indian Oceans (Dalebout et al. 2003). The distribution is not fully known, but it appears to be limited to the Indo-Pacific region (Culik 2004). The collected specimens are from Australia, Somalia, South Africa, the Maldives, Kenya, the Philippines, Taiwan and Japan. These beaked whales are relatively infrequently seen in the eastern tropical Pacific and may be more common in the western Pacific. They also appear to be more common in the western Indian Ocean, especially around the Maldives archipelago (Anderson et al. 2006).
Longman’s beaked whales are pelagic and feed in the deep sea. This conclusion is deduced from the extreme rarity of sightings and the lifestyles of related species. Also, a specimen was discovered off the coast of Japan in July of 2002. This specimen had distinctive bites from a Cookie cutter shark (Isistius brasiliensis). This shark species generally lives in the deep sea and its bites are common in deep sea marine life.
There is little habitat data for any of the species in the family Ziphiidae, but the preferred habitats are considered deep sea tropical marine environments. One study found that the maximum depth for this related species was 1267 meters. ("Indopacetus pacificus (Longman's beaked whale)", 2005; Johnson et al., 2004; Miller, 2005) Feeding Habits
The Japanese specimen’s stomach contents were analyzed, and revealed the beaks of Cephalopoda. (National Science Museum and Tokyo, 2002) Mollusks are also a part of the diet of this beaked whale.
Based on the distinctive bites visible on the Japanese specimen, cookie cutter sharks (Isistius brasiliensis) may feed on Longman’s beaked whales. The species large size makes this beaked whale unlikely prey. (National Science Museum and Tokyo, 2002; Whitehead et al., 2000)
Threats and Conservation Status
There is very little information on Longman's beaked whales, they are considered data deficient by the IUCN and are not listed by CITES or the U.S. Endangered Species Act.
The IUCN Red List notes that "the only estimates of abundance available are of 1,007 individuals (CV=126%) in the waters around Hawaii (Barlow 2006), and 291 (CV=100%) in the eastern North Pacific (Ferguson and Barlow 2001)." Further:
Direct hunting has never been associated with this species. Pervasive gillnet and longline fisheries throughout the species' range raises concern that some bycatch is likely. Even low levels of bycatch might cause unsustainable impacts on this naturally rare cetacean.
It is unknown if military, seismic or other loud noise-producing human activities resulted in the live stranding of a possible mother/calf pair in NE Taiwan (Wang and Yang 2006; Yang et al. 2008). However, “bubble-like lesions” were reported in at least one of these whales by Yang et al (2008). There is some evidence from Sri Lanka for occasional incidental or directed takes of animals identified as ‘bottlenose whales’ which are likely to be Indopacetus (Dayaratne and Joseph 1993).
Evidence from stranded individuals of several similar species of beaked whales indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.
This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).
The IUCN Red List classifies this species as Data Deficient. Both the US Federal List and CITES indicate no special status.
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