Hector's Beaked Whale

This species of beaked whale was named in 1871 after the James Hector, the curator of the Wellington Museum in New Zealand (now the Museum of New Zealand Te Papa Tongarewa).

Identification

This species of beaked whale is one the smallest of the beaked whales. It is known from only a few stranded animals. Hector's Beaked Whales are dark greyish-brown dorsally, paler ventrally and may have white or pale lower jaws. (Published descriptions of the colour pattern in this species are mainly based on specimens from California that are now known to be a different species.) The melon, which is not very prominent, slopes quite steeply to the short beak. Adult males have a pair of flattened, triangular teeth near the tip of the lower jaw. As with most other beaked whales, the teeth do not erupt in females. The dorsal fin is triangular to slightly hooked, small, and rounded at the tip. The leading edge of the dorsal fin joins the body at a sharp angle.

Hector's Beaked Whale may be confused with True's Beaked Whale, which also has a pair of triangular teeth set at the tip of the lower jaw in males. These two species may be indistinguishable at sea. True's Beaked Whale is larger in size, and the teeth of adult males are more forward-pointing than those of male Hector's Beaked Whales.

Accurate species identification is difficult for this and most other species of beaked whale, even for stranded animals. Identification of females and juveniles can be particularly problematic. While cranial anatomy and tooth morphology are useful, the distinguishing features may apply only to adults. Recently, molecular genetic techniques have been applied to the identification of beaked whales. A database of mitochondrial DNA sequences has been compiled for all known species, making it possible to reliably assign individual animals to a particular species. This approach was used recently to identify a live Hectors's Beaked Whale swimming close to shore at Safety Bay, Western Australia. A sample of sloughed skin for DNA analysis was obtained from this animal using a scrubby pad (kitchen pot scourer), which was passed along its flank as it swam past.

Similar species

True's Beaked Whale.

Distribution

Hector's Beaked Whale has a circumpolar distribution in cool temperate Southern Hemisphere waters between approximately 35° and 55°S. Four animals stranded in southern California, and two sightings in the area in the 1970s, were also thought to represent this species. However, recent work by Dalebout et al. (2002) using phylogenetic analyses of DNA sequence data has shown these Northern Hemisphere animals represent a new, previously unrecognized species of beaked whale. Despite their similar appearance, this new species, named Perrin's Beaked Whale (Mesoplodon perrini) after the famous American cetologist Dr W. F. Perrin, is not closely related to Hector's Beaked Whale.

Feeding and diet

Nothing is known about the diet of this species, although it is assumed to feed on deepwater squid and fish, and possibly crustaceans and echinoderms (sea urchins and starfish) found on the sea floor. Because they lack functional teeth, they presumably capture most of their prey by suction.

Life history cycle

Nothing is known about breeding in this species. Sightings are rare due to their deep-ocean distribution, elusive behaviour and possible low numbers.

References

• Bryden, M., Marsh, H. & Shaughnessy, P. 1998. Dugongs, Whales, Dolphins and Seals. A guide to the sea mammals of Australasia. Allen & Unwin, St Leonards.
• Carwardine, M. 2000. Whales, Dolphins and Porpoises. Dorling Kindersley, London.
• Dalebout, M. L., van Helden, A. van Waerebeek, K, and Baker, C. S. 1998. Molecular genetic identification of Southern Hemisphere beaked whales. Molecular Ecology 7: 687-694.
• Dalebout, M. L., Mead, J. G., Baker, C. S., Baker, A. N., and van Helden, A. L. 2002. A new species of beaked whale Mesoplodon perrini sp. n. (Cetacea: Ziphiidae) discovered through phylogenetic analyses of mitochondrial DNA sequences. Marine Mammal Science 18: 577-608.
• Gales, N. J., Dalebout, M. L., and Bannister, J. 2002. Genetic identification and biological observation of two free-swimming beaked whales: Hector's Beaked Whale (Mesoplodon hectori, Gray, 1871), and Gray's Beaked Whale (Mesoplodon grayi, Von Haast, 1876). Marine Mammal Science 18: 544-551.
• Mead, J. G. 1989. Chapter 14. Beaked whales of the genus Mesoplodon. In Handbook of Marine Mammals. Pp. 349-430. (Eds S. H. Ridgeway and S. R. Harrison.) Academic Press, London.
• Menkhorst, P. 2001. A Field Guide to Mammals of Australia. Oxford University Press, Melbourne, Australia.
• Reeves, R. R., Stewart, B. S., Clapham, P. J. and Powell, J. A. 2002. Hector's Beaked Whale. In National Audubon Society Guide to Marine Mammals of the World. Pp. 274-275. Chanticleer Press, Inc., New York.