Longman's Beaked Whale (Indopacetus pacificus)
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· Longman's beaked whales are one of the rarest cetaceans. Until fairly recently, this species was only known and described from two skulls found on beaches in Africa (in 1955) and Australia (in 1882, but described by Longman in 1926).
Longman's beaked whales, sometimes known as "tropical bottlenose" or "Indo-Pacific beaked whales," are one of the rarest and least known members of the beaked whale family (Ziphiidae). As adults, Longman's beaked whales can reach estimated lengths of about 20-30 ft (6-9 m); their weight is unknown. Compared to other beaked whales, this species is relatively large.
Longman's beaked whales have a large, robust body with a fairly large, "falcate" "dorsal" fin located far down their back. This species has dark, small, rounded, narrow flippers that fit into a depression on either side of the body. They have a well-defined "melon" (forehead) that is almost perpendicular to their long, tube-shaped beak. A crease may distinguish the melon from the beak. As they grow older, the melon develops into a steeper more bulbous shape that may hang over the beak. Like other beaked whales, they have V-shaped paired throat creases. As scientists have learned more about this species' external appearance and physical description, they have resolved confusion in various at sea sightings.
Longman's beaked whales have a relatively small, low, bushy blow that is usually visible and slightly angled forward. Longman's beaked whales generally have a darker grayish, bronze, brown, or olive coloration that extends from their blowhole and eye down their back, as well as a facial band. The melon and defined "thoracic" patch is lighter in color, sometimes described as "creamy" or pale. The upper jaw of the beak is darker and the lower jaw is lighter. The lower jaw has two conical shaped teeth located at the tip. Adult males have visible, erupted teeth (difficult to see in the field, especially when the mouth is closed), and may have linear and oval-shaped scars (e.g., bites from cookie-cutter sharks and lampreys) along their body.
Many species of beaked whales (especially those in the genus Mesoplodon) are very difficult to distinguish from one another (even when dead). At sea, they are challenging to observe and identify to the species level due to their cryptic, skittish behavior, a low profile, and a small, inconspicuous blow at the waters surface; therefore, much of the available characterization for beaked whales is to genus level only. Uncertainty regarding species identification of beaked whales often exists because of a lack of easily discernable or distinct physical characteristics.
Longman's beaked whales are usually found in tight groups averaging between 10-20 individuals, but occasionally have been seen in larger groups of up to 100 animals. They have sometimes been observed associating with other marine mammals such as pilot whales, spinner dolphins, and bottlenose dolphins. Dives may last from 14-33 minutes and their swimming style has been described as aggressive. This species is commonly misidentified when observed at sea.
The feeding behavior and prey of these cetaceans is generally unknown, but scientists believe it is similar to that of other beaked whales. Beaked whales are known to dive deep to forage for their food, possibly into the "sound channel." The analysis of stomach contents from one stranded specimen implies that cephalopods (e.g., squid and octopus) comprise the majority of the whale's diet.
Nothing is known about the reproduction or lifespan of this species. Due to the rarity, behavior, and infrequent encounters with this species, much of the information available is unreliable. A single young neonate calf was measured at 9.5 ft (2.9 m).
Longman's beaked whales live in generally warm (69.8-87.8° F, 21-31° C), deep (greater than 3,300 ft (1,000 m)), "pelagic" waters of tropical and subtropical regions.
Longman's Beaked Whale Range Map
(click for larger view PDF)
The distribution of Longman's beaked whales is poorly known and incomplete, but they are believed to occur in the tropical regions of the Indian and Pacific Oceans. In U.S. waters, this species has been sighted in the Hawaiian Exclusive Economic Zone (EEZ) and the equatorial tropical Pacific. Strandings (7 total events) have occurred on the coasts of East (Kenya and Somalia) and South Africa, northern Australia, the Maldives, the Philippines, South Japan, and Sri Lanka. Rare sightings have been documented in the eastern tropical Pacific Ocean. Sightings in the waters surrounding the Maldives archipelago and in the western Indian and Pacific Oceans are more frequent.
For management purposes, Longman's beaked whales inhabiting U.S. waters have been placed into a single Hawaiian stock. The population of Longman's beaked whales is unknown and no estimates exist. Based on a shipboard line-transect survey from 2002, the best available abundance estimate for the stock that occurs throughout the Hawaiian Islands "EEZ" is 370-770 individuals. There are insufficient data available on current population trends.
There are no known incidents or reports of this species being exploited by humans such as direct hunting. However, they have been recorded as bycatch in fisheries operating in Sri Lanka. Additionally, various types of fishing gear pose a risk of entangling or interacting with this species. This species of beaked whales may be sensitive to underwater sounds and anthropogenic noise. Anthropogenic noise levels in the world's oceans are an increasing habitat concern, particularly for deep-diving cetaceans like Longman's beaked whales that use sound to feed, communicate, and navigate in the ocean.
The IUCN Red List of Threatened Species considers this species "Data Deficient" due to insufficient information on population status and trends.
This species is protected under the Marine Mammal Protection Act of 1972, as amended.
|Stock Assessment Reports||n/a||various|
- NMFS Beaked Whales page
- NOAA's National Marine Mammal Laboratory (NMML) Beaked Whale Information
- Smithsonian National Museum of Natural History Marine Mammal Program Beaked Whale Identification Guide
- NMFS Ocean Acoustics Program
- Ocean Biogeographic Information System (OBIS-SEAMAP) Longmans' Beaked Whale Species Profile
- Reeves, R. R., P. A. Folkens, et al. (2002). Guide to Marine Mammals of the World. New York, Alfred A. Knopf. p. 266-267.
- Jefferson, T. A, M. A. Webber, and R. L. Pitman. (2008). Marine Mammals of the World, A Comprehensive Guide to their Identification. Amsterdam, Elsevier. p. 150-152.
- Shirihai, H. and B. Jarrett (2006). Whales, Dolphins and Other Marine Mammals of the World. Princeton, Princeton University Press. p.116-118.
Updated: December 12, 2012