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Overview

Distribution

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

The pygmy beaked whale is known from a handful of specimens and several dozen sighting from the eastern tropical/warm temperate Pacific, including the Gulf of California (Urban-Ramirez and Aurioles-Gamboa. 1992, MacLeod et al. 2006). These records extend from about 30°S to 28°N, and suggest that the species may be an eastern Pacific endemic. However, there is a single record of a stranding in New Zealand (Baker and Van Helden 1999), possibly suggesting that this species may have a more extensive distribution than previously believed. Alternatively, the New Zealand record may be an extralimital wandering.
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Geographic Range

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 )

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Standing distribution

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.

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Physical Description

Morphology

Physical Description

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

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Tooth Morphology

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.

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Skull morphology

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.

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External Morphology

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

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Type Information

Type for Mesoplodon peruvianus Reyes et al., 1991
Catalog Number: USNM 572998
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male;
Preparation: Cast
Collector(s): B. Luscombe
Year Collected: 1988
Locality: Huacho, Playa Paraiso, Lima, Peru, South America, South Pacific Ocean
  • Type: Reyes, J. C., et al. 1991. Marine Mammal Science. 7 (1): 1-24.
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Ecology

Habitat

tropical to warm temperate
  • UNESCO-IOC Register of Marine Organisms
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Habitat and Ecology

Habitat and Ecology
Like other members of the genus, it occurs in deep waters beyond the continental shelf.

The diet consists of small mid-water fishes, oceanic squids, and shrimps. Presumably these are taken at moderate to great depths.

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

Habitat Regions: tropical ; saltwater or marine

Aquatic Biomes: pelagic

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Depth range based on 4 specimens in 1 taxon.
Water temperature and chemistry ranges based on 3 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 20.785 - 24.724
  Nitrate (umol/L): 2.793 - 6.319
  Salinity (PPS): 34.053 - 35.252
  Oxygen (ml/l): 4.756 - 5.074
  Phosphate (umol/l): 0.523 - 1.004
  Silicate (umol/l): 3.577 - 5.680

Graphical representation

Temperature range (°C): 20.785 - 24.724

Nitrate (umol/L): 2.793 - 6.319

Salinity (PPS): 34.053 - 35.252

Oxygen (ml/l): 4.756 - 5.074

Phosphate (umol/l): 0.523 - 1.004

Silicate (umol/l): 3.577 - 5.680
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Trophic Strategy

Food Habits

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 )

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Associations

Predation

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.

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Known prey organisms

Mesoplodon peruvianus preys on:
Actinopterygii
Mollusca

This list may not be complete but is based on published studies.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.

Reviewer/s
Hammond, P.S. & Perrin, W.F. (Cetacean Red List Authority)

Contributor/s

Justification
There is almost no information on abundance and no information on trends in global abundance for this species. As a relatively uncommon species it is potentially vulnerable to low-level threats and a 30% global reduction over three generations cannot be ruled out (criterion A).

History
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
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IUCN Red List of Threatened Species: data deficient

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Population

Population
There are no estimates of global abundance for this species. Ferguson and Barlow (1999) estimate a total abundance of 32,678 beaked whales in the genus Mesoplodon in the eastern Pacific (corrected for missed animals). The majority of these were Mesoplodon peruvianus and Mesoplodon densirostris (Pitman and Lynn 2001).

Population Trend
Unknown
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Threats

Major Threats
Some pygmy beaked whales are caught incidentally in drift gillnets for sharks off Peru (Reyes et al. 1991).. Entanglement in fishing gear, especially gillnets in deep water (e.g., for billfish and tuna), is probably the most significant threat.

There is no information on global abundance or trends in abundance for this species. It is not believed to be uncommon but it is potentially vulnerable to low-level threats and a 30% global reduction over three generations cannot be ruled out

In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels has been implicated in mass strandings of a number of beaked whales including several Mesoplodon species and Indopacetus pacificus (Balcomb and Claridge 2001, Jepson et al. 2003, Cox et al. 2006, Wang and Yang 2006). Sound impacts may be important for all ziphiid species.

Pygmy beaked whales have been recorded ingesting plastic items, which may eventually lead to death (e.g. Scott et al. 2001).

Predicted impacts of global climate change on the marine environment may affect this species of whale, although the nature of impacts is unclear (Learmonth et al. 2006).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES. Research is needed to determine the impacts of potential threatening processes on this species.
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Relevance to Humans and Ecosystems

Risks

IUCN Red List Category

Data Deficient (DD)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Pygmy beaked whale

Pygmy beaked whale!<-- This template has to be "warmed up" before it can be used, for some reason -->

The Pygmy Beaked Whale (Mesoplodon peruvianus), also known as the Bandolero Beaked Whale, Peruvian Beaked Whale and Lesser Beak Whale, is the smallest of the Mesoplodonts and one of the newest discoveries. Interestingly, 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. Physical evidence of the species was first described in 1990 from Baja California, consisting of a skeleton and a rotting carcass.

Contents

Physical description

The body of the Pygmy Beaked Whale is the rather typical spindle shape of the genus, although the tail is unusually thick. The melon is somewhat bulbous and slopes down into a rather short beak. The mouthline in males has a very distinct arch with two teeth protruding slightly from the gum line before the apex. The coloration is typically dark gray on the top and lighter below, especially on the lower jaw, throat, and behind the umbililicus. Males may have a distinct pale "chevron" pattern on their back. The size for this species in only around 4.5 meters (13 feet long) in mature animals, and around 1.6 meters (5 ft) when born.

Population and distribution

This Beaked Whale has been recorded in the eastern tropical Pacific between Baja California and Peru through sightings and strandings. Another specimen, apparently of the same species, washed up in New Zealand, which indicates a presence in the western Pacific as well. No population estimates have been made.

Behavior

Little is known about the group behaviors of this whale, and small groups have been seen. Stomach contents reveal at least one specimen is a fish eater, as opposed to the squid normally eaten by the genus.

Conservation

This species may be quite vulnerable to gillnets in Peru, since scientists found 6 dead adults in a very small sample. However, there is not enough evidence to determine anything about the species.

Specimens

  • MNZ MM002142, collected from Oaro overbridge, south of Kaikoura, New Zealand, 19 October 1993.

References

  1. ^ Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. (2008). Mesoplodon peruvianus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of data deficient.

Sources

  • Encyclopedia of Marine Mammals. Edited by William F. Perrin, Bernd Wursig, and J.G.M Thewissen. Academic Press, 2002. ISBN 0-12-551340-2
  • Sea Mammals of the World. Written by Randall R. Reeves, Brent S. Steward, Phillip J. Clapham, and James A. Owell. A & C Black, London, 2002. ISBN 0-7136-6334-0
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