Cephalorhynchus heavisidii is found in coastal waters off of Africa’s Southwestern coast, from central Angola to the southern-most tip of South Africa. This species usually remain within 8 to 10 km of the shoreline, but has been sighted up to 45 nautical miles from the coast. While some studies suggest that Cephalorhynchus heavisidii does not migrate significant distances, and that there are resident dolphins in some areas, this is not well established. One study tracked a juvenile male that swam 158 km north of where he was tagged. Another juvenile male traveled 137 km north of his tagging site over a 17 month period, suggesting that average daily movements might be small. This species appears to have low population densities of around 5 individuals per 160 km.

Biogeographic Regions: ethiopian (Native )

Adult Heaviside’s dolphins typically weigh between 60 and 70 kg, with an average body length of 1.74 m. Maximum girth is roughly 67% of the length of the body. Each individual has between 48 and 70 teeth. They are distinguished from other dolphins by their blunt head, robust body, triangular dorsal fin, and rounded paddle-like flippers. Heaviside's dolphins have a dark gray anterior surface with a dark blue-black patch beginning midway between the dorsal fin and the snout, and extending about halfway down the ventral surface of the body. White markings on their underside form a three-pronged fork, with another white rhomboidal patch on the chest and two smaller diamond-like patches just posterior to the flippers. They also have a dark blue-black stripe, which extends from the blowhole to the cape. Sexual dimorphism has not been reported in this species.

Range mass: 60 to 75 kg.

Average length: 1.74 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

• Marine

Cephalorhynchus heavisidii is found exclusively in the Atlantic Ocean. Although it is most often found in waters less than 100 m deep, it has been sighted at depths up to 180 m. It is usually found in waters that are between 9 and 15ºC, but has been found in waters as warm as 19ºC. More than 87% of sightings occur in the Benguela Current.

Range depth: 180 (high) m.

Average depth: 100 m.

Habitat Regions: tropical ; saltwater or marine

Aquatic Biomes: pelagic ; coastal

The primary prey of Cephalorhynchus heavisidii includes hake and kingclip, which comprises nearly 49% of their diet. Octopods is also an important prey item for C. heavisidii, which makes up about 22% of their diet. The remainder of their diet generally consists of kingfish, gobies, and squid. Dolphins have fusiform, or torpedo shaped bodies, which allows them to swim at high speeds to avoid predation and catch prey.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore )

Cephalorhynchus heavisidii preys upon a number of different fish and cephalopods. Although this species is not a major prey item of any particular organism, body parts of dolphins have been found in the gut contents of killer whales and sharks. There is no information available regarding parasites of Cephalorhynchus heavisidii, nor has it been recorded to take part in any mutualistic or commensalistic relationships with other organisms.

Though Cephalorhynchus heavisidii is not typically vulnerable to predation, humans pose a potential threat due to by-catch. In general, dolphins are subject to retaliatory killings by local fisherman and are sometimes slaughtered for their meat, which is considered a delicacy in Japan. However, the biggest threat to dolphins seems to be accidental killing. Drift fishing nets catch everything in their paths, including dolphins, and prevent them from reaching the surface for air. It has been estimated that drift fishing nets have killed more than 30 million dolphins worldwide since the 1960's.

Known Predators:

• Humans (Homo sapiens)

Heaviside’s dolphins communicate visually, as dolphins have exceptional underwater vision. They also use tactile communication, swimming near other individuals and rubbing against one another to build affiliative relationships. Acoustically, they are able to communicate through a series of whistles and clicks ranging between 1.5 and 11.0 KHz. They communicate chemically by releasing pheromones from pores in their anal glands. Heaviside’s dolphins also rely heavily on echolocation to perceive their surroundings.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; acoustic ; echolocation

There is no information available regarding the average lifespan of Cephalorhynchus heavisidii in captivity or in the wild. The average lifespan of most wild delphinids ranges from 17 to 25 years, with a few living into their early 50s. Although similar averages are found for captive dolphins, few captive individuals live past their 20s. In general, delphinids are vulnerable to bacterial, fungal, and viral infections and have been found to suffer from heart and respiratory disease, stomach ulcers, and even cancer. Dolphins are also vulnerable to a number of different parasites including flukes, tapeworms, and roundworm.

There is no information available regarding the mating system of Heaviside's dolphins. However, bottlenose dolphins, spinner dolphins, and common dolphins are promiscuous.

Heaviside's dolphins breed once every 2 to 4 years from spring to late summer. Gestation lasts for 10 to 11 months. Females usually give birth to only one offspring at a time, as there is limited space for in utero development. To account for the limited space in the uterus, during development, the tail flukes and dorsal fins of fetuses are cartilaginous and fold over. Newborns average 85 cm in length. Birth mass has not been recorded for this species. However, newborn bottlenose dolphins range from 11.3 to 18.1 kg, and Irrawaddy dolphins, which average 96 cm in length at birth, has an average birth mass of 12.3 kg. There is no information available regarding weaning and time to independence for this species. Bottlenose dolphins begin weaning as early as 32 months and are fully weaned by 48 months, while time to independence ranges between 3 and 6 years. Female Heaviside's dolphins reach sexual maturity between 5 and 9 years of age, and males reach sexual maturity between 6 and 9 years of age.

Breeding interval: Haviside's dolphins breed every 2 to 4 years.

Breeding season: Haviside's dolphins breed from spring to late summer.

Range gestation period: 10 to 11 months.

Range age at sexual or reproductive maturity (female): 5 to 9 years.

Range age at sexual or reproductive maturity (male): 6 to 9 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Cephalorhynchus heavisidii calves swim in echelon position, that is, in close proximity to the mid-lateral flank near the dorsal fin of the mother. This allows the calf extra speed at a lower tailbeat frequency, because it is able to ride along the pressure wave that its mother’s body creates. However, it has been shown that this causes extra strain on the mother, who is able to swim at only 76% of her mean maximum speed when swimming by her self. Most dolphin calves develop strong social bonds with their mother, which remains even at 3 years of age. This extended mother-young association is thought to be due largely to the still-improving physical performance and social skills of calves. There is no information available regarding paternal investment in calf development.

Parental Investment: precocial ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning

Cephalorhynchus heavisidii is listed as “data deficient” on the IUCN Red List of Threatened Species. CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) lists Cephalorhynchus heavisidii under Appendix II, meaning that though this species is not necessarily threatened with extinction, its trade must be regulated so that its survival is not jeopardized. Cephalorhynchus heavisidii is vulnerable to harpoons and guns used by humans hunting close to shore, where about 100 are killed annually. Also, entanglement in fishing gear poses a significant threat. In 1983, 67 were caught in nets off Namibia, and 57 off of South Africa. Although overfishing of their primary prey may pose a threat to their survival, little evidence exists to support this claim. As an inshore species, C. heavisidii is susceptible to pollution and boat traffic, and low levels of DDT have been found in some individuals. This species is currently protected from commercial hunting and fishing throughout its geographic range. It is also protected by a 322 km Exclusive Fishery Zone (EFZ) off the coast of South Africa and a 20 km EFZ off the coast of Namibia.

CITES: appendix ii

IUCN Red List of Threatened Species: data deficient

There are no known adverse effects of Cephalorhynchus heavisidii on humans. Although local fisherman may contend that this species decreases local fish abundance, there is no documented evidence to support this.

Cephalorhynchus heavisidii provides no known economic benefits to humans.