Mesoplodon layardii (Gray, 1865)

Russell A. Mittermeier & Don E. Wilson, 2014, Ziphiidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 326-357 : 352-353

13.

Strap-toothed Whale

Mesoplodon layardii

French: Baleine-a-bec de Layard / German: Layard-Zweizahnwal / Spanish: Zifio de Layard

Other common names: Layard’s Beaked Whale, Strap-toothed Beaked Whale

Taxonomy. Ziphius layardii Gray, 1865 ,

type locality not given, probably South Africa.

This species is monotypic.

Distribution. Occurs from the temperate waters of S Atlantic, Indian, and S Pacific oceans to the waters of Antarctica. A record from Burma (= Myanmar) is thought to represent a vagrant individual.

Descriptive notes. Total length 550-625 cm; weight 1000-1300 kg. Female Strap-toothed Whales are c¢.5% larger than males. Body is spindle-shaped, with greatest girth around its midpoint. Flukes are wide in relation to body length, and tailstock is compressed laterally. Dorsal fin is small and set approximately two-thirds the distance between tip of the beak and end ofthe tail. Straptoothed Whales are a mix of black and yellowish-gray or white. Rostrum and lower jaw form a long, distinct beak, and there are two grooves on the throat. Adult males have a single tusk on each side of the lowerjaw; these tusks are positioned approximately halfway along the jaw line. Tusks are approximately triangular in maturing males, but in fully adult males, they can be up to 30 cm long and cross over the top of the upper jaw, apparently limiting the extent to which individuals can open their jaws, but this does not seem to interfere with feeding.

Habitat. Primarily waters greater than 200 m deep. As with other species of Mesoplodon , Strap-toothed Whales may be more common in areas of complex seabed topography, but thisstill has to be confirmed.

Food and Feeding. Strap-toothed Whales consume a wide variety of species of deepwater squid. Although tusks of adult males appearto limit the extent to which they can open their jaws, this does not appear to affect feeding ability. In common with other species of beaked whales, Strap-toothed Whales likely forage at depths greater than 500 m for much of their lives.

Breeding. Female Strap-toothed Whales give birth to a single offspring after gestation thatis likely twelve months. Offspring are likely to remain dependent on their mothers for at least one year.

Activity patterns. There is no information available for this species.

Movements, Home range and Social organization. There is no specific information available for this species, but sightings of Strap-toothed Whales at sea tend to be of relatively small groups of five or fewer individuals. Nothing is known about the typical composition of these groups.

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The IUCN Red List. There are no estimates of global population size of the Straptoothed Whale. Like other species of beaked whales, the Strap-toothed Whale is potentially affected by ingestion of plastic debris and noise pollution, and individuals may be caught as bycatch in driftnet fisheries. As a species restricted to cooler waters, Strap-toothed Whales also may be vulnerable to impacts of climate change. Nevertheless, nothing is known about the form or extent of these potential impacts.

Bibliography. Macleod et al. (2006), Mead (1989b), Sekiguchi et al. (1996).

Figures

1. Baird’s Beaked Whale (Berardius baiwrdu), 2. Arnoux’s Beaked Whale (Berardius arnuxu), 3. Cuvier’s Beaked Whale (Ziphius cavirostris), 4. Northern Bottlenose Whale (Hyperoodon ampullatus), 5. Southern Bottlenose Whale (Hyperoodon planifrons), 6. Shepherd’s Beaked Whale (Tasmacetus shepherd), 7. Longman’s Beaked Whale (Indopacetus pacificus), 8. Hubbs’s Beaked Whale (Mesoplodon carlhubbsi), 9. Stejneger’s Beaked Whale (Mesoplodon stejnegeri), 10. Pygmy Beaked Whale (Mesoplodon peruvianus), 11. Perrin’s Beaked Whale (Mesoplodon perrini), 12. True’s Beaked Whale (Mesoplodon marus), 13. Strap-toothed Whale (Mesoplodon layardii), 14. Hector’s Beaked Whale (Mesoplodon hectori)

Distribution. Occurs from the temperate waters of S Atlantic, Indian, and S Pacific oceans to the waters of Antarctica. A record from Burma (= Myanmar) is thought to represent a vagrant individual.