Mesoplodon hotaula, Deraniyagala, 1963

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 : 355-356

17.

Deraniyagala’s Beaked Whale

Mesoplodon hotaula

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

Taxonomy. Mesoplodon hotaula Deraniyagala, 1963 ,

Sri Lanka, washed ashore “in a dying condition” on 26 January 1963 at Ratmalana (6° 49’ N, 79° 52’ E), approxiately 8 km south of Colombo, on the west coast of Sri Lanka.

Historically, there has been confusion about whether or not M. hotaula represents a species in its own right. It was originally described in 1963 from an animal which stranded in Sri Lanka, but based on morphological similarities, J. C. Moore and R. M. Gilmore synonymized it with M. ginkgodens in 1965. However, recent molecular analysis, published in 2014, has resulted in M. hotaula being resurrected as a species in its own right. Monotypic.

Distribution. Warmer waters ofthe Pacific and Indian oceans in an area ranging from E Africa, S India and Sri Lanka to Galapagos Is, and possibly as far as Central and South America. Exact distribution remains unclear due to the small number of known strandings, and the taxonomic confusion between the Deraniyagala’s Beaked Whale and the Ginkgo-toothed Beaked Whale (M. ginkgodens ).

Descriptive notes. Total length ¢.400-450 cm; weight ¢.1000 kg (unconfirmed). Body of the Deraniyagala’s Beaked Whale 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. Colorationis typically dark on top and light ventrally, with a pale lowerjaw and chin. Rostrum and lowerjaw form a beak that is indistinct from the low sloping forehead. There are two grooves on the throat. Adult males have a single tusk on each side of the lower jaw. Tusks are positioned approximately one-third of the way along the mandibles. In common with Ginkgo-toothed Beaked Whales, male Deraniyagala’s Beaked Whale may lack anyof the long, pale, linear scars caused by tusks of other males that are found on males of most species of beaked whales, but this is based on information from a single individual. However, broken tusks on two specimens suggests that aggressive male—male combat (the cause ofsuch scars) may occur.

Habitat. Primarily waters greater than 200 m deep. Nothing further is known about habitat preferences of Deraniyagala’s Beaked Whales.

Food and Feeding. There is no specific information available for this species, but in common with other species of beaked whales, Deraniyagala’s Beaked Whale are thought to consume deep-water squid and, to a lesser extent, deep-water fish. They likely forage at depths greater than 500 m.

Breeding. There is no information available for this species.

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 Deraniyagala’s Beaked Whaleslikely occur in small groups.

Status and Conservation. As a new species, Deraniyagala’s Beaked Whale has not yet evaluated. However,it is mostlikely it will be listed on CITES Appendix II (along with most other beaked whales) and classified as Data Deficient on The IUCN Red List. There are no estimates of global population size of the Deraniyagala’s Beaked Whale. Like other species of beaked whales, the Deraniyagala’s Beaked Whale is potentially affected by ingestion of plastic debris and noise pollution, and individuals can be killed as bycatch in driftnet fisheries. Nevertheless, nothing is known about the form or extent of these potential impacts.

Bibliography. Dalebout et al. (2014), Moore & Gilmore (1965).

Figures

On following pages: 18. Sowery's Beaked Whale (Mesoplodon bidens); 19. Blainville’s Beaked Whale (Mesoplodon densirostris); 20. Andrews's Beaked Whale (Mesoplodon bowdoini); 21. Spade-toothed Whale (Mesoplodon traversil); 22. Gervais's Beaked Whale (Mesoplodon europaeus).

Distribution. Warmer waters ofthe Pacific and Indian oceans in an area ranging from E Africa, S India and Sri Lanka to Galapagos Is, and possibly as far as Central and South America. Exact distribution remains unclear due to the small number of known strandings, and the taxonomic confusion between the Deraniyagala’s Beaked Whale and the Ginkgo-toothed Beaked Whale (M. ginkgodens ).