Cephalorhynchus heavisidii
Heaviside's dolphin

Coastal waters of southwestern Africa (Nowak 1999).

Sightings of this dolphin have been made from the breaker zone to 45 nautical miles offshore, and in water depths up to 180 m, but the species is most abundant in the inshore region in depths of less than 100 m. Heaviside's dolphins have been found across a wide range of surface temperatures, but most sightings have been in water from 9 to 15 degrees Celsius (Best and Abernethy 1999).

Heaviside's dolphin reaches physical maturity at about 1.68-1.70 m in total length. It is a strongly built animal, its maximum girth averaging almost two-thirds of the body length. The head is cone shaped without a pronounced beak, and there are 24-35 teeth on each side of each jaw. The lower jaw invariably projects beyond the tip of the snout. The eyes are small and situated just above and behind the angle of the gape. The blowhole is on top of the head at about the same or slightly behind the level of the eyes (Reeves 1999, Nowak 1999).

Basically C. heavisidii is a dark blue-black above with a grey "cape" over the head and thoracic region. A roughly diamond-shaped wedge of white runs across the chest with its lateral extremities curling around and terminating immediately in front of each flipper insertion. A trident-shaped white mark extends in the midline from about the level of the posterior insertion of the flippers to the anus, but with a lateral tongue-like extension up either side. This basic color pattern seems to be present at birth. Certain color variants in adults, notably partially albinistic individuals have been reported (Reeves 1999, Nowak 1999).

Heaviside's dolphins are usually found in small groups of from one to 10 animals, with two being the most common number. On some occasions, two groups can be found in close association, and it is possible that amalgamation into larger groups may occur. The overall proportion of calves in the groups is about 10%. Apart from the incidence of calves, nothing is known about the sex or age composition of these groups (Reeves 1999).

Certain groups of C. Heavisidii appear to be year round residents of particular areas. However, this remains an open question, as there is only limited evidence indicating this movement pattern (Reeves 1999).

Aerial displays by Heaviside's dolphins are comparatively rare. Individuals have been seen engaging in "tail-flips", where the animal leaps clear of the water but throws its tail high in the air, so that while its head re-enters the water with the body roughly vertical to the sea surface, the momentum of the jump carries the tail section past the vertical. The impression gained is of a rapid forward somersault (Reeves 1999).

There is some evidence indicating that Heaviside's dolphins readily associate with sailing and/or motorized craft, sometimes "escorting" them for many hours (Reeves 1999).

Demersal fish such as hake (Merluccius capensis) and kingklip (Genypterus capensis) form about half of the diet of Heaviside's dolphin. Other prey include octopods, gobies (Sufflogobius bibarbatus) and squid (Loligo reynaudi). This species seems to feed on bottom-dwelling organisms, demersal species that may migrate off the bottom (even to the surface) at night, and pelagic species that can be found from the surface to near the sea floor on the continental shelf (Reeves 1999).

All species of Cephalorhynchus are subject to accidental killing by fisherman and crabbers; the genus is considered to be especially vulnerable to coastal purse seining. The extent to which C. heavisidii is depleted by hunting is unknown, although it is reported that the species is sought after for its meat; there may be some hunting by harpoon (Nowak 1999, Reeves 1999, Fertl 1999).

The name for this dolphin comes from the Greek "kephale" for "head" and "rhynchos" for "nose" or "snout" because the snout, which is about half the length of the skull, is well-differentiated from the rest of the head. Captain Haviside (the first "e" was added in error) was an employee of the British East India Company; he carried the type specimen from the Cape of Good Hope to England in 1827 (Fertl 1999).