Pygmy Beaked Whales, Mesoplodon peruvianus
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Description & Behavior
Pygmy beaked whales, Mesoplodon peruvianus (Reyes, Mead and Van Waerebeek, 1991), also known as lesser or Peruvian beaked whales, are one of the latest discovered and smallest members of the genus Mesoplodon. Their maximum known length is only 3.9 m, with males thought to be slightly larger than females. Adult males have scarred black and white bodies while those which are smaller and uniformly brown to dark gray above and lighter below, with relatively little scarring, are thought to be females and juveniles. Pygmy beaked whales have moderately long beaks, and low triangular dorsal fins with slightly falcate (curved) or straight trailing edges that are shaped like those of harbor porpoises. The pygmy beaked whale's most distinctive characteristic are their teeth which are extremely small and egg-shaped in cross section. Most groups sighted so far have been of 2-4 animals. The behavior of these animals appears to be similar to that of other species of mesplodonts though very little is yet known about this species.
Beaked Whales (Family Hyperoodontidae)
These medium-sized to moderately large whales have a single pair of grooves on their throats. They have distinct snouts, and often the few teeth present are visible only in adult males. They have a single nostril or blowhole. Beaked whales are generally slender with small dorsal fins toward the rear on their backs. The rear edge of their flukes (tails) usually lacks a well-defined notch. These whales are deep divers and are rarely seen. Many species are known only from a few specimens, and little is known about the life history and biology of the group. All members of this family, except Blainville's beaked whales, are difficult to distinguish from each other, and study by museum experts is usually necessary for identification.
World Range & Habitat
Pygmy beaked whales, Mesoplodon peruvianus, are known only from a handful of specimens and several sightings from the eastern tropical Pacific and Gulf of California, as well as off Peru and possibly Chile. There is a single record of a stranding of one in New Zealand, suggesting that this species may have a more extensive distribution.
Feeding Behavior (Ecology)
Conservation Status & Comments
Little is known of the pygmy beaked whale's conservation status or threats. Major threats described by the IUCN Red List for this species are:
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).
References & Further Research
Center for Cetacean Research and Conservation (CCRC) - Beaked whales (+ videos)
Dalebout, M. L. 2002. Species identity, genetic diversity, and molecular systematic relationships among the Ziphiidae (beaked whales). Ph.D. dissertation, University of Auckland, New Zealand.
Pitman, R. L. 2002. Mesoplodont whales Mesoplodon spp. Pp. 738-742 in W. F. Perrin, B. Würsig and J. G. M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Pitman, R. L., A. Aguayo-L., and J. Urban-R. 1987. Observations of an unidentified beaked whale (Mesoplodon sp.) in the eastern tropical Pacific. Marine Mammal Science 3:345-352.
Pitman, R. L., and M. S. Lynn. 2001. Biological observations of an unidentified mesoplodont whale in the eastern tropical Pacific and probable identity Mesoplodon peruvianus. Marine Mammal Science 17:648-657.
Reyes, J. C., J. G. Mead, and K. Van Waerebeek. 1991. A new species of beaked whale Mesoplodon peruvianus sp. n. (Cetacea Ziphiidae) from Peru. Marine Mammal Science 7:1-24.
G. Paolo Sanino, José L. Yáñez, and Koen Van Waerebeek, 2007, A first confirmed specimen record in Chile, and sightings attributed to the lesser beaked whale Mesoplodon peruvianus Reyes, Mead and Van Waerebeek, 1991, Boletin del Museo Nacional de Historia Natural, Chile, 56: 89-96.
Research Mesoplodon peruvianus » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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