Shepherd's Beaked Whale

Shepherd's Beaked Whales, are known only from less than thirty stranded animals and a few unconfirmed sightings of live animals.

Alternative name/s

Tasman Whales

Identification

The species was described by W. B. B. Oliver in 1937 from a nearly complete skeleton collected by Mr G. Shepherd, a curator at the Wanganui Alexander Museum in New Zealand. The skeleton of this whale is now on display in the Wanganui Regional Museum.

Shepherd's Beaked Whales are dark brownish-black above and paler on the sides and belly. There may be a light patch on the front of the head. A pale area, continuous with the belly colouration, extends onto the sides above, and in front of, the flippers. The body and flanks may also have light longitudinal or diagonal patches on each side. Shepherd's is the only species of beaked whale with a full set of functional teeth in the upper and lower jaws of both sexes. There are 17-21 teeth in the upper jaw and 17-28 in the lower jaw. Adult males have an additional larger pair of teeth near the tip of the lower jaw. Based on comparisons with other beaked whales, the calves should be about 3m in length at birth. The dorsal fin is about 0.3m high, hooked, and positioned far back on the body, between 60 and 70% of the distance from the beak, to the tail flukes. The beak is distinct from the forehead and is slender at the tip, almost pointed. The melon is moderately developed and has a broad, steep front. The flippers are short and tapered.

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. Generally, while cranial anatomy and tooth morphology are useful, the distinguishing features may apply only to adults. However, the presence of a full set of teeth in both sexes makes the identification of stranded Shepherd's Beaked Whales comparatively straightforward.

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.

Distribution

Shepherd's Beaked Whales are found only in the Southern Hemisphere, in deep, cool offshore waters between 30°S and 50°S. Most strandings have occurred in New Zealand, with others found in Western Australia, South Australia, South America and South Africa.

Feeding and diet

Little is known about the diet of this species. The stomach of one stranded female from Argentina contained bottom-dwelling fish and crabs. They probably also feed on squid, and possibly echinoderms (sea urchins and starfish) found on the sea floor.

Life history cycle

These whales are mainly known from stranded dead animals. They are rarely seen at sea due to their deep-ocean distribution, elusive behaviour, and possible low numbers, so virtually nothing is known of the breeding and general behaviour of this species. The female found in Argentina was 6.6m long and seemed to be reproductively mature.

References

• Baker, A. N. 1999. Whales and Dolphins of Australia and New Zealand: an identification guide. Allen & Unwin, St Leonards.
• 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.
• Mead, J. G. 1989. Chapter 12. Shepherd's beaked whale Tasmacetus shepherdi Oliver, 1937. In Handbook of Marine Mammals. Pp. 309-320. (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. Shepherd's Beaked Whale. In National Audubon Society Guide to Marine Mammals of the World. Pp. 264-265. Chanticleer Press, Inc., New York.