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Longman’s Beaked Whale (Indopacetus pacificus)

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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 feet (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 feet (2.9 m).

This species is classified as DATE INCOMPLETE according to the IUCN's Red List.
This species is classified as DATE INCOMPLETE according to the IUCN’s Red List.

Status

MMPA – Longman’s beaked whales, like all marine mammals, are protected under the MMPA.
CITES Appendix II – throughout its range

Species Description

Weight:
unknown
Length:
20-30 feet (6-9 m)
Appearance:
darker grayish, bronze, brown, or olive colored, large, robust body with dark, small flippers
Lifespan:
unknown
Diet:
unknown, but one stranded whale was found with cephalopods like squid and octopus in its stomach
Behavior:
usually found in tight groups averaging between 10-20 individuals, but occasionally have been seen in larger groups of up to 100 animals

RELATIVE SPECIES: Southern Bottlenose Whale, Cuvier’s

OTHER NAMES: Tropical Bottlenose Whale, Indo-Pacific Beaked Whale

NEIGHBORING SPECIES: Arnoux’s Beaked Whale.

THREATS: Bycatch, vessel noise

DIET: Squid and Octopus

MANNER OF FEEDING: Deep foraging

BEHAVIOR: Travel in small to large groups up to 100. Sometimes seen with Pilot Whales and Bottlenose Dolphins. Pods are close knit. “Aggressive” swimmers.

REPRODUCTION: Unknown

LIFE SPAN: Unknown

TOOTHED or TOOTHLESS (BALEEN): Toothed

FRESHWATER, SALTERWATER or BRACKISH: Saltwater

Habitat

Longman’s beaked whales live in generally warm (69.8-87.8° F, 21-31° C), deep (greater than 3,300 feet (1,000 m)), “pelagic” waters of tropical and subtropical regions.

Distribution

They are believed to occur in the tropical regions of the Indian and Pacific Oceans. 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.

Strandings have occurred on the coasts of East and South Africa, northern Australia, the Maldives, the Philippines, South Japan, and Sri Lanka.

In U.S. waters, this species has been sighted in the Hawaiian Exclusive Economic Zone (EEZ) and the equatorial tropical Pacific.

Population Trends

The population of Longman’s beaked whales is unknown. The most recent stock assessment reports with population estimates of the U.S. population, in Hawaii, are available on our website.

Threats

  • bycatch in fisheries operating in Sri Lanka.
  • entanglement in fishing gear
  • underwater sounds and anthropogenic noise, particularly for deep-diving cetaceans like Longman’s beaked whales, since they use sound to feed, communicate, and navigate in the ocean

Conservation Efforts

This species is protected under the Marine Mammal Protection Act of 1972, as amended.

Regulatory Overview

This species is protected under the Marine Mammal Protection Act of 1972, as amended.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Ziphiidae
Genus: Indopacetus
Species: pacificus

References:

  • 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.

Cool/Gross/Weird:

  • They 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 were originally placed in the Mesoplodon genus (given the name Mesoplodon pacificus in 1926), but due to differences in features of the skull they have been reclassified as their own genus, Indopacetus.

-TSF-

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