Heaviside'S Dolphin

Heaviside's are small and stocky with adults reaching a maximum length and weight of 1.7 m (5.6 ft) and 75 kg (165 lb) respectively. The dolphin has a distinct black, grey and white body pattern, and is not easily confused with any other species in its range. The head is cone shaped with a blunt beak. The dorsal fin is triangular in shape and centred in the middle of the back. The head and thorax are coloured light grey with darker patches around the eye. The dorsal fin, fluke and dorsal cape are a dark grey to almost black with a band that extends forward from the dorsal fin to the blowhole. The underbelly is white, with bands that extend onto the lower rear of the body. Small white patches are located just behind the pectoral fins and a single white patch extends between these fins on the chest.

The species is strongly associated with the cool waters of the Benguela Ecosystem. Although the southern limit of the range is defined as Cape Point, the real southern limit beyond which sightings are extremely rare is Hout Bay, some 40 km (25 mi) to the north (a considerable distance for a species which shows very high site fidelity to quite small spatial scales when nearshore). The species occurs more or less continuously for 2,500 km (1,600 mi) to the north of this along the South African coast, through Namibia and into southern Angola where the northern boundary for the species remains poorly defined.

Levels of predation are unknown; however, killer whales (Orcinus orca) are known predators and there is evidence of shark attack from body scars.

Information on reproduction is limited for Heaviside's dolphins, however they are thought to be comparable to Hector's and Commerson's dolphins. Females and males reach sexual maturity approximately between 5–9 years. Mating is thought to occur year-round, however individual females may only produce calves every 2–4 years. Gestation time is unknown. Maximum known lifespan is based on the oldest recorded individual at 26 years old.

No total abundance estimate currently exists, however a population estimate of 6,345 for the region between Table Bay and Lamberts Bay, South Africa represents the southernmost populations in the species range. Local population estimates for Walvis bay and Lüderitz are 508 and 494 respectively. A visual and acoustic line-transect ship survey estimated an average of 1594 dolphins in the Namibian Islands' Marine Protected Area (NIMPA), which spans 400 km (250 mi) of coastline along southern Namibia (REF Martin et al. 2020). Quantification of abundance throughout the range is still required.