Cephalorhynchus heavisidii (Gray, 1828)

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 : 525

35.

Heaviside’s Dolphin

Cephalorhynchus heavisidii

French: Dauphin de Heaviside / German: Namibia-Delfin / Spanish: Delfin de Heaviside

Other common names: Benguela Dolphin, Haviside's Dolphin, South African Dolphin

Taxonomy. Delphinus heavisidii Gray, 1828 ,

“Inhab. Cape of Good Hope,” Western Cape Prov., South Africa.

This species is monotypic.

Distribution. Coastal waters of SW Africa from c.17° S in Angola to Cape Point at ¢.34° S in South Africa.

Descriptive notes. Total length up to 170 cm; weight up to 75 kg. Neonates are thought to be 80-85 cm long. Like other species of Cephalorhynchus , Heaviside’s Dolphin has robust, stocky body with blunt, poorly defined beak. Flippers are slender and paddle-shaped with rounded tips. Dorsalfin is large and triangular with wide base. Anterior edge of dorsal fin may be slightly convex or bulged. Skin is mostly dark gray, although darker cape and face are still distinguishable. Cape starts at blowhole and runs as narrow band along dorsal surface before widening just anterior to dorsal fin and dipping down onto flanks and tail. There is white patch on chest in front of flippers, and white patches occurjust behind flippers in “armpit” area. Most of ventral body behind flippers extending to urogenital area is also white, and slightly in front of posterior edge of dorsal fin, two slender lobes arch onto lower flanks. There are 22-28 pairs of small conical teeth in each jaw.

Habitat. Prefers nearshore shallow waters less than 100 m deep within 8-10 km of shore and sea-surface temperatures of 9-15°C. Heaviside’s Dolphin is restricted to 1600 km of coast in south-western Africa and appears sparse throughout its distribution. Sightings of Heaviside’s Dolphin are most frequent in the Cape Town region of South Africa. It also seems to associate with cool waters of the Benguela Current.

Food and Feeding. Heaviside’s Dolphin feeds on demersal and pelagic fish and cephalopods. Commonly recorded prey species include shallow-water Cape hake ( Merluccius capensis ), kingklip (Genypterus capensis ), bearded goby (Sufflogobius bibarbatus), Cape Hope squid ( Loligo reynaudi), and various octopods. Sightings of Heaviside’s Dolphin are more frequent in areas exposed to swells with greater abundance of hake.

Breeding. There is no specific information available for this species, but breeding may occur more frequently during summer.

Activity patterns. Little is known about behavioral patterns of Heaviside’s Dolphins. They seem to be generally energetic; observers typically describe them as quick and agile. They may “porpoise” and breach while traveling, and they occasionally ride bow waves of boats. Heaviside’s Dolphins produce typically narrow-band, high-frequency echolocation clicks of ¢.125 kHz.

Movements, Home range and Social organization. Heaviside’s Dolphin is generally observed in groups of fewer than ten individuals and most commonly in pairs. Larger aggregations of up to 30 individuals have occasionally been reported. Associations with the Dusky Dolphin ( Lagenorhynchus obscurus ), which are apparently neutral in nature, have also been observed. Movement patterns of Heaviside’s Dolphin are not well known, butit is generally thought to be resident in small local areas throughout its distribution. Home range estimates are 302-1028 km? and abundance varies diurnally. Heaviside’s Dolphins move inshore during morning and offshore during afternoon and evening,likely to feed on hake that move closer to the surface at night. Inshore preference during the day may be associated with predator avoidance (mainly offshore shark).

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The [UCN Red List. There are currently no abundance estimates or population trends available for Heaviside’s Dolphins. They are apparently the most commonly sighted cetaceans off the Namibian coast, and abundance is 3573-11,267 individuals in the Cape Town region. Small cetaceans have full legal protection within the distribution of Heaviside’s Dolphin, but direct kills, usually with harpoons or guns, still occur. Heaviside’s Dolphin is also vulnerable to incidental catch in beach seines, purse seines, trawls, and gillnets along coasts of South Africa and Namibia, but there are little data on mortality and catch rates. Heaviside’s Dolphin is a coastal species, but human population densities are low in most of its distribution, so pollution and boat traffic are not currently major threats.

Bibliography. Best & Abernethy (1994), Dawson (2009), Elwen, Meyer et al. (2006), Elwen, Reeb et al. (2009), Elwen, Thornton et al. (2010), Jefferson et al. (2008), Morisaka et al. (2011), Reeves, Crespo et al. (2008c).

Figures

On following pages: 33. Commerson’s Dolphin (Cephalorhynchus commersonii); 34. Chilean Dolphin (Cephalorhynchus eutropia); 35. Heaviside's Dolphin (Cephalorhynchus heavisidii); 36. Hector’s Dolphin (Cephalorhynchus hector).

Distribution. Coastal waters of SW Africa from c.17° S in Angola to Cape Point at ¢.34° S in South Africa.