Perrin's beaked whale (Mesoplodon perrini) is the newest species of beaked whale to be described. It was first found in May 1975 off the coast of California, with four more specimens appearing in September 1997. They were initially identified as Hector's beaked whale (Mesoplodon hectori), except for the most recent one which was assumed to be a neonate Cuvier's beaked whale^[2]. Following inclusion of one of these specimens in a mtDNA sequence database of beaked whales, it turned out that they seemed well distinct from M. hectori (Dalebout et al. 1998). It was subsequently confirmed that the other "Hector's" specimens from California belonged to the same undescribed taxon (Dalebout 2002). The new species was formally described in 2002 by Dalebout et al.; its common and specific names are a tribute to cetologist William F. Perrin.

Despite the superficial similarities to the (entirely allopatric) Hector's Beaked Whale, this species is closely related to the pygmy beaked whale, the next most recently described species, and probably represents its Northern Hemisphere sister species.

Perrin's Beaked Whale has not definitely been recorded alive by scientists. However, its appearance is known from the beached specimens, and following resolution of their identity as a new species, it seems highly likely that 3 supposed "Hector's Beaked Whales" which were seen off California in 1976 (2 individuals) and 1978 (one individual) were actually this species (Mead 1981, Dalebout et al. 2002).

Description

Perrin's Beaked Whale cannot be identified with absolute certainty at sea. However, the combination of small size, appearance and presumed range makes a confusion unlikely. Stranded specimens can be identified as this species by either DNA sequence data and/or anatomical details of the skull.(Dalebout et al. 2002)

This species has a fairly typical body shape for a mesoplodont with a small head, long body, and deep tail. The rostrum of this whale is shorter than every other mesoplodont other than Hector's Beaked Whale and the Pygmy Beaked Whale, especially in young individuals. The mouthline of this species is straight, and the melon forms a small bulge with a crescent-shaped blowhole with forward-pointing tips. The teeth on this species are fairly large and towards the tip of the mouth. Throat grooves are present on this species. The mature male specimen was 3.9 meters in length (13 feet) and the female was 4.4 meters (14 feet 8 inches) in length; the immature males measured between 2.1 and 2.45 meters (7-7.5 ft).

The coloration is dark gray above and white below in the holotype male, with a lighter gray underside of the tail fluke. A white patch is present near the navel. The coloration of females is not known, since the only specimen was rather decomposed. Calves are light to dark gray on top, and white below, including the lower jaw and throat; the uinderside of the flukes is lighter gray. There is a dark "mask" on the head, from the corners of the mouth to the eye region, the rostrum, and the melon, and there are white stripes on the tail underside. The adult male had the typical white scar-stripes from fights with conspecifics. Only adult males seem to have teeth, and even these only two, in line with other Mesoplodon species. In Perrin's beaked whale, the teeth are located near the tip of the lower jaw and are roughly equilateral triangles when viewed laterally and still placed in the jaw; in this they resemble the foreteeth of Baird's beaked whale more than those of the Mesoplodon species which are otherwise similar.(Dalebout et al. 2002)

A photograph of a possible living specimen - one of the 2 observed in 1976 - is featured in Rice (1978: 95) as "Mesoplodon carlhubbsi", a distinctly larger species also native to the waters off California. Recordings of the animals' vocalizations were also made on this opportunity.(Mead 1981)

Distribution and status

This species has only been found off the coast of California between San Diego and Monterey. It likely lives offshore the Pacific coast of North America - and possibly elsewhere in the northern Pacific - in waters 1,000 meters deep or more. However, evidence is lacking and the northern and southern limits of its range are entirely unknown (though biogeography of beaked whales suggests it does not reach the Equator). No population estimate or assessment of conservation status has hitherto been possible. San Clemente Island holds a sonar research facility of the US Navy; such research has in the past been implicated in causing strandings of cetaceans (see Beached whale).

Ecology and behavior

Nothing is known of this species' behavior in life. However, as this is apparently quite similar in all Mesoplodon, a number of well-founded assumptions can be made.

The males of this species seem to engage in fights like most other mesoplodonts. Scars from fighting are present on this species, although the precise mechanism of combat is enigmatic: given the teeths' position near the lower jaw tips, it can be expected that the scars consist of two parallel lines; only single scar lines were present on the adult male however suggesting glancing blows rather than direct attacks created them.

Few stomach contents were available for analysis. Presumably, this species eats pelagic squid (such as Octopoteuthis deletron, remains of which were found in the female's stomach) and possibly small fish^[3] like other beaked whales.

The largest immature LAM 088901, at 2.45 meters of length, was apparently independent from its mother. On the other hand, the smallest known specimen USNM 504259 had a fringed tongue which indicates that it was still suckling. Teeth were not present in the immatures^{[verification needed]}, but they are not needed for feeding. The dates when the specimens were found suggest that the young start to feed independently in summer; considering that most whales suckle until around one year of age suggests that the young are born during the summer half of the year. Consequently, as they are all of somewhat similar size, the immatures were probably around one year old. The adults were both an estimated 9 years old when they died.

The causes of death of 2 animals can be tentatively inferred: The 1997 specimen was starving at the time of death, possibly following a parasite infection (Dalebout et al. 2002). The 1975 female had died around May 14 (Mead 1981); given that the juvenile found on May 22 was apparently its calf and that it was not yet fully weaned, its death seems to be a direct consequence of the loss of its' mother.

As with their relatives, cookiecutter sharks attack this whale to try and bite off chunks of flesh. Such attacks are generally not life-threatening to the whale. It is a host of the thoracican barnacle Conchoderma auritum, and for one or several species of parasitic Phyllobothrium cestodes (possibly Phyllobothrium delphini) this species is either a primary or a dead-end host.

Specimens

1. USNM 504259 - May 22, 1975; 33°15'N, 117°26'W - the smallest specimen, an immature male
2. USNM504260 - May 28, 1975; 33°16'N, 117°26'W - an adult, the only female known to date and probably the mother of USNM 504259 (Dalebout et al. 2002)
3. USNM504853 - September 9, 1978; 33°07'N, 117°20'W - an adult male, the holotype
4. LAM 088901 JRH 052 - December 27, 1979; 32°55'N, 117°15'W - an immature male
5. TMMC-C75 - September 18, 1997; 36°37'N, 121°55'W - an immature male

The 1976 possible sightings took place on July 30, the 1978 one on September 9 - the same day the holotype specimen was discovered (Mead 1981). Altogether, there is a marked concentration of sightings between May and September. It is unknown if this has any significance. Nonetheless, with the scant data at hand it still appears that looking for small beaked whales during the summer months in the area between Santa Catalina and San Clemente Islands and the mainland has the best odds of encountering this enigmatic species.

References

Cetaceans portal

• Baker, Alan N. (1990): Whales and dolphins of New Zealand and Australia: An identification guide. Victoria University Press, Wellington.
• Carwadine, M. (1995): Whales, dolphins and porpoises. HarperCollins, London.
• Dalebout, Merel L. (2002): Species identity, genetic diversity and molecular systematic relationships among the Ziphiidae (Beaked Whales). Ph.D. thesis, School of Biological Sciences, University of Auckland, Auckland, New Zealand. HTML abstract
• Dalebout, Merel L.; van Helden, Anton L.; van Waerebeek, K. & Baker, C. Scott (1998): Molecular genetic identification of southern hemisphere beaked whales (Cetacea: Ziphiidae). Molecular Ecology 7(6): 687-694. doi:10.1046/j.1365-294x.1998.00380.x PDF fulltext
• Dalebout, Merel L.; Mead, James G.; Baker, C. Scott; Baker, Alan N. & van Helden, Anton L. (2002): A New Species of Beaked Whale, Mesoplodon perrini sp. n. (Cetacea: Ziphiidae), Discovered Through Phylogenic Analysis of Mitochondrial DNA Sequences. Marine Mammal Science 18(3): 577-608. doi:10.1111/j.1748-7692.2002.tb01061.x PDF fulltext
• Henshaw, M.D.; Leduc, R.G.; Chivers, S.J. & Dizon, A.E. (1997): Identification of beaked whales (family Ziphiidae) using mtDNA sequences. Marine Mammal Science 13(3): 487-495. doi:10.1111/j.1748-7692.1997.tb00656.x (HTML abstract)
• Jefferson, T.A.; Leatherwood, S. & Webber, M.A. (1993): FAO species identification guide: Marine mammals of the world. United States Environment Programme & Food and Agriculture Organization of the United Nations (FAO), Rome. PDF fulltexr
• Mead, James G. (1981): First records of Mesoplodon hectori (Ziphiidae) from the northern hemisphere and a description of the adult male. Journal of Mammalogy 62(2): 430-432. doi:10.2307/1380733 (First page image)
• Mead, James G. (1984): Survey of reproductive data for the beaked whales (Ziphiidae). Report of the International Whaling Commission Special Issue 6: 91-96.
• Mead, James G. (1989): Beaked whales of the genus Mesoplodon. In: Ridgway, S.H. & Harrison, R. (eds.): Handbook of marine mammals Vol.4: 349-430. Academic Press, London.
• Mead, James G. (1993): The systematic importance of stomach anatomy in beaked whales. IBI Reports 4: 75-86.
• Mead, James G. & Baker, Alan N. (1987): Notes on the rare beaked whale, Mesoplodon hectori (Gray). Journal of the Royal Society of New Zealand 17: 303-312.
• Messenger, S.L. & McQuire, J.A. (1998): Morphology, molecules and the phylogenetics of cetaceans. Systematic Biology 47(1): 90-124. doi:10.1080/106351598261058 (HTML abstract)
• Reeves, Randall R. & Leatherwood, S. (1994): Dolphins, porpoises and whales: 1994-98 Action plan for the conservation of cetaceans. IUCN, Gland, Switzerland. ISBN 2-8317-0189-9
• Rice, D.W. (1978): Beaked whales. In: Haley, D. (ed.): Marine mammals of the eastern North Pacific and Arctic waters: 88-95. Pacific Search Press, Seattle.

Footnotes