Lagenodelphis hosei, Fraser, 1956

Russell A. Mittermeier & Don E. Wilson, 2014, Delphinidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 410-526 : 502-503

12.

Fraser's Dolphin

Lagenodelphis hosei

French: Dauphin de Fraser / German: Borneo-Delfin / Spanish: Delfin de Fraser

Other common names: Bornean Dolphin, Fraser's Porpoise, Hose's Dolphin, Sarawak Dolphin, Shortsnout Dolphin, White-bellied Dolphin

Taxonomy. Lagenodelphis hosei Fraser, 1956 ,

mouth of Lutong River, Malaysia.

This species is monotypic.

Distribution. Tropical and subtropical distribution in all major oceans from ¢.30° N to ¢.30° S.

Descriptive notes. Total length up to 270 cm (males) and up to 260 cm (females); weight over 210 kg. Neonates are 100-110 cm long and weigh 15-20 kg. Fraser’s Dolphin has robust, stocky build; short, nearly triangular, slightly falcate dorsal fin (more triangular in adult males); and small, slender flippers with pointed tips. Beak is short and stubby but well defined. Male Fraser’s Dolphins may have large post-anal protrusion. Back and flanks are dark gray or brown, and belly, throat, and lower jaw are white, sometimes with pinkish tinge. Beak tips and lips are dark, and there is dark longitudinal stripe between beak tip and melon base. Dark lateral stripe extending from face to urogenital area along gray-white border characterizes Fraser’s Dolphin. This lateral stripe only becomesvisible at pre-pubescence or pubescence and tends to be wider in older individuals, especially males. There is also stripe that runs from lower jaw to leading edge offlipper joint. In adults, this stripe merges with lateral stripe, giving appearance of black facemask. Young Fraser’s Dolphins are paler, have more muted pattern, and do not have prominent lateral band or facemask. White areas also tend to be especially pinkish. Atlantic populations of Fraser’s Dolphin tend to be larger in size, with a less prominent lateral stripe. There are 38-44 pairs of conical teeth in each jaw.

Habitat. Prefer deep offshore waters with depths of more than 1000 m but also occur in near-shore waters, as shallow as 100 m orless, close to deep water along coasts. Fraser's Dolphins are typically found in tropical and subtropical regions, and they seem to occur only as a vagrant in waters around France and the UK. They are more abundant in equatorial areas of the eastern tropical Pacific Ocean and less common in the Atlantic Ocean, but this could be because of disparities in survey effort. Fraser’s Dolphins use near-shore waters, close to deep waters, off coasts of the Philippines, Taiwan, some Caribbean Islands, and the Indo-Malay Archipelago. In equatorial regions of the eastern tropical Pacific Ocean, abundance is associated with upwelling and warm subtropical surface water. This habitat is shared with the Sperm Whale (Physeter macrocephalus), the Short-finned Pilot Whale ( Globicephala macrorhynchus ), the Short-beaked Common Dolphin ( Delphinus delphis ), the Striped Dolphin ( Stenella coeruleoalba ), and the Melonheaded Whale ( Peponocephala electra ). Habitat in the eastern tropical Pacific Ocean is partitioned among these species and those that prefer tropical surface water characterized by a shallow, mixed layer and a shallow, sharp thermocline: the Pantropical Spotted Dolphin ( Stenella attenuata ), the Spinner Dolphin ( Stenella longirostris ), and the Rough-toothed Dolphin ( Steno bredanensis ). Fraser's Dolphin is also associated with the warm water of the Agulhas Current off South Africa.

Food and Feeding. Fraser’s Dolphins prefer mesopelagic fish, squid, and crustaceans. Myctophids and chauliodontids seem to be the dominant prey families off the Philippines. Preferred squid genera include Abraliopsis, Onychoteuthis , Histioteuthis , and Chiroteuthis. Preferred crustaceans include Notostomus elegans, Acanthephyra quadrispinosa, and A. carinata. Fraser’s Dolphin is thought to be a deep diver and forages at depths up to 600 m, but it also has been observed foraging at the water’s surface. This suggests a degree of foraging plasticity, and an ability to exploit a wide area of the water column. Distribution of Fraser’s Dolphin overlaps with that of Risso’s Dolphin ( Grampus griseus ) and the Pantropical Spotted Dolphin, and the three species seem to partition their habitat by preferred foraging zones. Fraser’s Dolphin tends to exploit deeper mesopelagic and benthic zones, Risso’s Dolphin tends to exploit shallower zones, and the Pantropical Spotted Dolphin tends to forage closer to the water’s surface.

Breeding. Mating system of Fraser’s Dolphin is thought to be promiscuous. Breeding is known to peak during spring and autumn offJapan and during summer off South Africa. Gestation is thought to be ¢.12-5 months, and birth interval is c.2 years. Males reach sexual maturity at 7-10 years of age, and females at 5-8 years. Longevity is at least 19 years.

Activity patterns. Fraser’s Dolphins are generally shy and do not readily approach boats. They are not known to bow-ride in the eastern tropical Pacific Ocean, but they may occasionally do so in other regions. Fraser’s Dolphin is a fast swimmer and may make long, low leaps out of the water while traveling.

Movements, Home range and Social organization. Fraser’s Dolphin travels in large groups of several hundred or thousands of individuals. These groups may be mixedspecies and can include Melon-headed Whales, Short-finned Pilot Whales, Risso’s Dolphins, Spinner Dolphins, Pantropical Spotted Dolphins, Common Bottlenose Dolphins ( Tursiops truncatus ), and sometimes even Sperm Whales.

Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. Fraser's Dolphin is widespread and abundant. Global abundance estimate is more than 300,000 individuals, and there are no major known threats or reported population declines. There are 289,300 individuals in eastern tropical Pacific Ocean, 16,836 individuals in Hawaiian waters, 13,518 individuals off the Philippines and in the Sulu Sea, and 726 individuals in the northern Gulf of Mexico. Fraser’s Dolphin may be opportunistically taken in hand-harpoon fisheries throughout the Lesser Antilles; off Sri Lanka, Indonesia, Philippines, and Taiwan; and likely in much of the Indo-Pacific Ocean. They are also occasionally taken in Taiwanese and Japanese drive fisheries. In the Philippines, they may be used as bait in other fisheries and human consumption. Fisheries operating from northern Mindanao and Palawan kill ¢.800 Fraser’s Dolphins/year. Fraser’s Dolphins are occasionally caught incidentally in tuna purse seines in the eastern tropical Pacific Ocean, but the catch rate seems to be low. Between 1971 and 1975, 26 Fraser’s Dolphins were reported killed by this fishery. They may also be caught in gillnets and driftnets in Taiwan, Sri Lanka, Philippines, Ghana, and likely other regions throughout the tropical Pacific Ocean. Fraser’s Dolphins sometimes are caught in trap nets offJapan and anti-shark nets around South Africa. Organochlorine contaminants such as PCBs may be a threat in some areas of industrialized Asia.

Bibliography. Dolar (2009), Dolar et al. (2003), Hammond et al. (2008i), Jefferson et al. (2008), Minh et al. (2000), Perrin, Leatherwood & Collet (1994), Wang, J.Y. & Yang Shihchu (2007), Wang Mingchih et al. (2012), Weir, C.R. et al. (2008).

Figures

On following pages: 11. Long-beaked Common Dolphin (Delphinus capensis); 12. Fraser's Dolphin (Lagenodelphis hosel); 13. Tucuxi (Sotalia fluviatilis); 14. Guiana Dolphin (Sotalia guianensis); 15. Indo-Pacific Humpback Dolphin (Sousa chinensis); 16. Atlantic Humpback Dolphin (Sousa teuszii).

Distribution. Tropical and subtropical distribution in all major oceans from ¢.30° N to ¢.30° S.