Andrews' beaked whale

Andrews' beaked whale, scientifically known as Mesoplodon bowdoini, is one of the least understood species within a genus already noted for its elusive nature. This cetacean is known to science solely through specimens that have washed ashore on beaches; there are no confirmed sightings of live individuals in their natural habitat. This scarcity of direct observation makes it one of the most enigmatic of the beaked whales.

Taxonomy and Discovery

The species was formally described in 1908 by American scientist Roy Chapman Andrews, based on a specimen discovered at New Brighton Beach in Canterbury Province, New Zealand, in 1904. The whale was named in honor of George S. Bowdoin, a significant supporter and trustee of the American Museum of Natural History.

Physical Characteristics

Andrews' beaked whale is a medium-sized member of its family, with adult males typically measuring between 3.4 and 4.4 meters (11.2 to 14.4 ft) in length, and females slightly larger, ranging from 3.7 to 4.9 meters (12.1 to 16.1 ft). Calves are estimated to be around 2.2 meters (7.2 ft) at birth. While precise weight data is unconfirmed, mesoplodonts of similar size are generally recorded between 1 and 1.5 tons. The whale possesses a robust, spindle-shaped body, a low melon, and a short, thick beak. A distinctive feature is the pair of large, flattened tusks that erupt from the arched lower jaw only in adult males; in females, these teeth remain unerupted within their less-arched jawline. Adult males are characterized by their dark brown or black coloration, contrasted by a pale lower jaw and rostrum tip. Females display a bluish-gray to slate gray dorsal surface, transitioning to paler sides and underside, and also share the pale to whitish lower jaw and rostrum tip. Both sexes may exhibit a small, light patch in front of the eye. Subadult males can closely resemble females before their tusks develop. Calves are dark on their dorsal side and light ventrally, with a noticeable dark eye patch.

The flippers are small and narrow, set relatively low on the body. Behind the flippers are slight depressions known as 'flipper pockets,' which are thought to enhance streamlining during dives. The dorsal fin is small, triangular, and positioned far back on the body. The flukes are broad relative to the body and typically lack a prominent median notch.

Behavior and Diet

Andrews' beaked whales are presumed to be deep-diving, echolocating suction feeders. Similar to other beaked whales, they possess a pair of V-shaped throat grooves. These are believed to aid in suction feeding by creating negative pressure within the mouth as the tongue retracts and the throat grooves expand, effectively drawing prey inward like a biological vacuum. Although the specific diet of this species is unknown, it likely includes deep-sea squid and fish.

Social behavior is not well documented, but like other Mesoplodon species, they may form small pods consisting of 1 to 5 individuals. Adult males are notable for extensive, linear pale to white scarring across their bodies, which contrasts sharply with their dark skin. These scars are hypothesized to be the result of tusk use in male-male combat, possibly related to competition for access to females. The calving season is suggested to occur during summer and autumn off New Zealand, but other behavioral aspects remain largely unrecorded.

Predators and Distribution

The primary natural predators of Andrews' beaked whale are believed to be killer whales and large sharks. Both sexes commonly show evidence of cookiecutter shark activity, with numerous small, pale circular or oval healed wounds, sometimes concentrated around the genitals and sides.

Andrews' beaked whales inhabit the Southern Hemisphere, although their precise geographic range is uncertain. Approximately 48 stranded specimens have been recorded across Australia, New Zealand, Macquarie Island, the Falkland Islands, and Tristan da Cunha. This distribution pattern suggests a potential circumpolar presence, but this remains unconfirmed by direct sightings.

Conservation

Andrews' beaked whale has never been documented as a target of hunting, nor are there any records of it becoming entangled in fishing gear. The species is also protected under the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).