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Mesoplodon peruvianus
Reyes, Mead and Van Waerebeek, 1991
English: Peruvian beaked whale, lesser beaked whale, pygmy beaked whale
German: Peruanischer Schnabelwal
Spanish: Ballena picuda peruana
French: Mésoplodon du Pérou
Family Ziphiidae
Mesoplodon peruvianus © Wurtz-Artescienza (see
links
).
1. Description
M. peruvianus
is the smallest of all Mesoplodon species. It has a small, triangular dorsal fin and a short, narrow beak. The head is also narrow and the melon not as bulbous as in some other species. There are two teeth on the middle of the lower jaw (gape) in males and the mouthline has a slight to moderate arch. Peruvian beaked whales are dark grey in colour, which fades to light grey on the undersides. Maximum known body length is 3.7 - 3.9 m (Reyes et al. 1991, Urbán-Ramírez and Aurioles-Gamboa 1992). According to Pitman (2009) adult males have a broad white swathe across the body that forms a conspicuous chevron when viewed from above, however no such individuals sighted at sea have been validated as M. peruvianus by a specimen or molecular genetic analysis.
2. Distribution
The Peruvian beaked whale was first described in 1991, based on captured and stranded specimens collected in 1976-1989 from the coast of Peru, between Playa Paraiso (11°12'S) and San Juan de Marcona (15°19'S) (Reyes et al., 1991). Recent findings of Sanino et al. (2007) extend the southernmost known distribution in the Eastern Pacific to 29°17'S, or 14º of latitude (1,550km) farther south than the most austral, published record in Peru.
Distribution of
Mesoplodon peruvianus
(Taylor et al. 2008; © IUCN;
enlarge map
). Peruvian beaked whales are found in the eastern Pacific, from northern Mexico to central Chile and off New Zealand (Pitman, 2002; Jefferson et al. 2008; Sanino et al., 2007).
Several dozen sightings of
Mesoplodon
species "A" , tentatively identified as probable
M. peruvianus
by Pitman and Lynn (2001), from the eastern tropical/warm temperate Pacific, including the Gulf of California extend from about 10°S to 28°N, have led several authors to suggest that the species may be an eastern Pacific endemic (Urbán-Ramírez and Aurioles-Gamboa 1992, MacLeod et al. 2006; Pitman, 2009). The Chilean and New Zealand (at 42º31'S) specimens (Baker and Van Helden, 1999), sightings near Choros, and the species' common occurrence in Peru's cool coastal waters (Sanino et al. 2007) question the hypothesis by Urbán-Ramírez and Aurioles-Gamboa (1992) who proposed the Eastern Tropical Pacific (ETP) as the core distribution area of
M. peruvianus
, believing that the records on the Peruvian coast are 'close to the limit of their southern range (15°S).
3. Population size
Ferguson and Barlow (2001) 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 they argued were
M. peruvianus
and
M. densirostris
.
4. Biology and Behaviour
Sanino et al. (2007) report on three sightings (5 individuals) off north-central Chile in waters 20-70m deep, suggesting at least occasional nearshore presence of lesser beaked whales in neritic habitat, an unusual ecological trait for ziphiids, considered to be almost exclusively oceanic. It is unclear whether the sighting of a neonate in February, suggesting calving in summer may be the key to this inshore occurrence. Sightings attributed to M. peruvianus consisted of small groups of 1-3 individuals (n=5), consistent with typical ziphiid behaviour.
5. Migration
Unknown.
6. Threats
The neritic distribution (see above) would explain why lesser beaked whales are so often captured in Peru's artisanal drift gillnet fishery for sharks (Reyes et al., 1991).
Sanino et al. (2007) report on a specimen off north-central Chile showing bullet injuries in the skull presumably originating from a high-powered handgun, which is the first circumstantial evidence of such a case. Entanglement in fishing gear, especially gillnets in deep water (e.g., for billfish and tuna), is probably another significant threat in the ETP (Taylor et al. 2008). Furthermore, cetaceans inhabiting waters surrounding the coastal islands off north-central Chile are facing threats that include direct catches and unregulated whale-watching operations (Sanino et al. 2007).
7. Remarks
Documented range states: Peru, Chile, Mexico, New Zealand (based on: Reyes et al. 1991; Urbán-Ramírez and Aurioles-Gamboa, 1992; Baker and van Helden, 1999; Sanino et al. 2007). Inferred range states: Colombia; Costa Rica; Ecuador; El Salvador; Guatemala; Honduras; Mexico; Nicaragua; Panama (Taylor et al. 2008).
The species is categorised as "Data Deficient" by the IUCN. M. peruvianus is not listed by CMS but is listed in Appendix II of CITES.
8. Sources and further information
see "
Genus Mesoplodon - Beaked whales: Introduction and Sources
"
© Boris Culik (2010) Odontocetes. The toothed whales: "
Mesoplodon peruvianus
". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza. © Maps by IUCN.
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