Heaviside's dolphin Cephalorhynchus heavisidii, is a small delphinid (maximum body length 1.74 m, maximum body weight 74.4 kg) that is endemic to the cool waters of the Benguela current which runs equatorward along the southwestern coast of Africa. The species' range extends across the continental shelf from Cape Point in South Africa northwards into the waters of southern Angola. Heaviside's dolphins appear to display fidelity to defined areas of range. Geographic variation in both mitochondrial and nuclear DNA markers has suggested the existence of multiple populations but was unable to delineate their geographic extent. Several surveys have generated estimates of abundance over parts of the species' range. The most extensive ran from 2012–14 and produced an estimate of 1594 (95 percent (CI) 776-3275) Heaviside’s dolphins using an area of 21,305 km² encompassing the Namibian Islands Marine Protected Area and adjacent waters offshore. Heaviside's dolphins exhibit strong diurnal movements inshore and offshore. In South Africa, offshore movement at night has been linked to them intercepting prey which migrate off the bottom to aggregate in the upper 20 m of the water column. Heaviside's dolphin also forages close to the bottom in shallow waters, taking several demersal fish and cephalopod species. Monitoring with satellite-linked depth recorders revealed 90 percent of dives were to depths less than 30 m. Only a handful of dives were recorded to depths exceeding 70 m. Heaviside's dolphins are usually found in small groups composed of 1-10 individuals. Aggregation of animals into groups of four or more individuals appears to be a catalyst for increased social interaction, punctuated by conspicuous behaviors such as tail slapping and aerial leaping. The species produces a range of pulsed signals, mainly sequences of narrow-bandwidth high frequency (NBHF) clicks with a centroid frequency (FC) around 125 kHz with little or no energy below 100 kHz that appear to be primarily used for echolocation. Occasionally, signals composed of broad-bandwidth clicks are also produced. These appear to serve as a means of maintaining communication in Heaviside's dolphin groups. There is no evidence of sexual dimorphism in size or growth rate, although the coloration of the genital region is distinct in males and females. Sexual maturity occurs at a body length of 1.56–1.59 m in both sexes. Size at birth is likely to be about 87 cm. The interbirth interval is unknown. Heaviside's dolphins are susceptible to entanglement in fishing gear. The most acute risk is posed by monofilament gillnets which; although prohibited in Namibia since 1987, are still used on both the west coast of South Africa and in southern Angola. Assays of PCBs, DDT, hexachlorobenzene (HCB) and a range of heavy metals in blubber samples suggest that Heaviside's dolphins is exposed to low levels of contaminants in the Benguela ecosystem relative to those encountered by small cetaceans in the Northern Hemisphere. Heaviside's dolphin is vulnerable to future range contraction and population decline driven by a warming climate as it is adapted to a circumscribed area of cool-water habitat which is surrounded by warm tropically influenced water masses. The species is an important focus for boat-based tourist excursions in both South Africa and Namibia and this creates potential for disturbance.