Lesser Beaked Whale

Humans are the only known threat to M. peruvianus. This whale becomes tangled in fishing nets, which initially led to the discovery of this species.

Little is known about M. peruvianus due to its inaccessible habitat and elusive nature.

Mesoplodon peruvianus has several common names. Among them are Lesser Beaked Whale, Peruvian Beaked Whale and Pygmy Beaked Whale (The Whale and Dolphin Conservation Society, Cetacea and Texas A&M University - Corpus Christi, 2001).

Texas A&M University - Corpus Christi reports that M. peruvianus can most easily be mistaken for Hector's beaked whale (Texas A&M University - Corpus Christi, 2001).

Perception Channels: tactile ; chemical

IUCN Red List of Threatened Species: data deficient

Although feeding by M. peruvianus has not been witnessed, it is believed that this species eats mid- to deep-sea fish and squid (Cetacea, 2001).

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

Mesoplodon peruvianus was discovered in Peru in 1991 and is only known in Peruvian waters, although there have been two documented strandings on Mexican shores (The Whale and Dolphin Conservation Society, 2001). Strandings and captures have taken place between 11 and 15 degrees south latitude, off the coast of central and southern Peru. This is thought to be the southern end of the range of M. peruvianus (Texas A&M University - Corpus Christi, 2001).

Biogeographic Regions: neotropical (Native ); pacific ocean (Native )

This species lives in mid- to deep-sea waters off of the Peruvian coast.

Habitat Regions: tropical ; saltwater or marine

Aquatic Biomes: pelagic

At birth, M. peruvianus is between 1.5-1.6 m long, while the adult is between 3.4-3.7 m. This whale is the smallest species of Mesoplodon (World Biodiversity Database, 2001). This species is, on its upper side, uniformly dark gray fading to light gray on the underside (dark gray posterior to the navel). The body is spindle-shaped. The short, dark-tipped beak precedes a narrow head with an indentation at the blowhole. This species has two tiny teeth on its lower jaw. The small, triangular dorsal fin has a wide base and is positioned far behind the center of the animal. The flukes have no notches, and their tips are slightly pointed. (All information from Texas A&M University - Corpus Christi, 2001 unless otherwise noted.)

M. peruvianus exhibits sexual dimorphism. The males of the species are larger than the females (World Biodiversity Database, 2001).

The features that distinguish this Mesoplodon species from others of its genus are most prominent in males (Webb, 1998).

Range length: 3.4 to 3.7 m.

Other Physical Features: endothermic ; bilateral symmetry

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

Head Shape The melon bulges slightly anterior to the blowhole and slopes smoothly to the short beak. The mouthline arches strongly in males, though this sinusoidal curves is less pronounced in females and juveniles. Coloration Adults of both sexes have a similar pigmentation pattern. Dark gray dorsally, laterally, and grading to a lighter gray ventrally, especially posterior to the navel and on the underside of the beak. The coloration of calves reflects adult color, brown on dorsum and lateral sides and becoming grayish white on the ventral surface. The lighter color also extends up posterior and dorsal to the eye. The beak is grayish white with a brown tip, small brown patches are present near the angle of the mouth and between the throat grooves. Size Adult body length range is unknown. Recorded maximum body length for adult males and females is 3.7 m and 3.6 m, respectively. Length at birth is 1.6 m. Most Likely Confused With: Mesoplodon densirostris Mesoplodon perrini

Diagnostic features of the skull and mandible On the vertex of the dorsal skull the premaxillary bone extends forward of the nasal and frontal bones. Separates from Berardius and Ziphius. A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their combined middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus. When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon. Tooth alveoli of mandible are positioned posterior to the mandibular symphysis .Separates from M. bidens, M. bowdoini, M. carlhubbsi, M. europaeus, M. grayi, M. hectori, M. layardii, M. perrini, and M. traversii. Right premaxilla extends posteriorly beyond the right nasal a distance exceeding 70% of dorsal length of right nasal. Separates from M. gingkodens. Antorbital notches form acute angles. Separates from M. densirostris and M. stejnegeri.

Stranding Distribution Known from strandings and by-catch in Pacific waters of southern California, Mexico, and Peru. One stranding is recorded from New Zealand, though this animal is possibly extralimital. The total species range includes much of the eastern tropical Pacific, as well as the western South Pacific.

Tooth position A single pair of teeth are positioned on the elevated section of the mandible. Subadult animals have teeth that are inclined anteriorly at an angle of 20 to 40 degrees relative to the long axis of the mandible. However, in adult males the long axis of the teeth are almost perpendicular to the long axis of the mandible. Tooth exposure Erupted teeth in adult males are covered by gum tissue, with only the tip of tooth exposed. Females and juveniles do not have erupted teeth. Tooth shape The teeth are are ovate in cross section.

The pygmy beaked whale is the most recently described member of the genus, and appears to be the smallest of the species of Mesoplodon. They tend to be dark grey above and lighter below, apparently with little scarring. They have small, triangular, wide-based dorsal fins that are shaped like those of harbour porpoises. The most distinctive characteristic is the teeth, which are extremely small and egg-shaped in cross-section (although generally they are not visible in sightings at sea). Can be confused with: The small triangular dorsal fin is different from that of most other species of Mesoplodon, but using this character alone, it would be very difficult to dismiss the possibility of other species in sightings at sea.

This is the smallest known species of Mesoplodon; maximum known length is 3.7 m, apparently with males larger than females. At birth, these animals are about 1.6 m long.

Groups of 2 or 3 animals have been observed.The diet consists of small mid-water fishes, oceanic squid, and shrimps.

Pygmy beaked whales are taken in the driftnet fishery for sharks off the coast of Peru . IUCN: Insufficiently known.

The pygmy beaked whale (Mesoplodon peruvianus), also known as the bandolero beaked whale, Peruvian beaked whale and lesser beaked whale, is the smallest of the mesoplodonts and one of the newest discoveries. There were at least two dozen sightings of an unknown beaked whale named Mesoplodon sp. A before the initial classification, and those are now believed to be synonymous with the species. The species was formally described in 1991, based on ten specimens obtained from Peru between 1976 and 1989, including a 3.72 m (12.2 ft) adult male as the type specimen. A specimen that stranded at Paracas, Peru in 1955 (first tentatively identified as Andrews' beaked whale) has since been identified as a pygmy beaked whale. Since 1987, there have been an additional 40 sightings of the species, for a total of 65 (as of 2001).

A species of the eastern Pacific, but one record from New Zealand.

tropical to warm temperate

Data Deficient (DD)