Cephalorhynchus heavisidii (Gray,
English: Heaviside's dolphin
Spanish: Delfín del Cabo
French: Céphalorhynque du Cap
Cephalorhynchus heavisidii © Wurtz-Artescienza (see links).
All dolphins of the genus are small, blunt-headed and chunky. Because
they don't have a beak, they are often wrongly called porpoises.
Their flippers are rounded and almost paddle-shaped. The dorsal
fin is proportionally large and triangular (Dawson, 2009). The fore
half of the body is uniformly grey, with the dorsal cape, fin, flanks
and keel being dark blue-black. A similarly-coloured stripe runs
from the blowhole to the cape. The flippers and eye patch are the
The underside is white, with white 'armpits' behind the flippers
and a rhombus shape on the chest. A finger-shaped patch extends
from the belly along each flank. Adults grow to around 1.74 m long
and weigh around 75 kg (Dawson, 2009).
Heaviside's dolphins range in close inshore waters of southwestern
Africa, from northern Namibia (17°09'S) south to Cape Point
in Cape Province (34°21'S) (Rice, 1998; Dawson, 2009). The range
is restricted and fairly sparsely populated throughout. C. heavisidii
occurs only along approximately 1,600km of shoreline (Carwardine,
1995). There are no authenticated sightings or beach-cast specimens
of the species east of Cape Point, and this seems to mark the southern
and eastern limit of distribution. The northern limit is less well
defined, as records extend along the entire west coast of South
Africa and Namibia. As the cetacean fauna of Angola is very poorly
known, it is uncertain how much farther north the distribution of
Heaviside's dolphin might extend (Best and Abernethy, 1994).
Distribution of Cephalorhynchus
heavisidii (Reeves et al. 2008): cold coastal waters
from central Namibia to southern South Africa (© IUCN; Click
here for large map).
3. Population size
No reasonable estimate is possible from the available data. Griffin
and Loutit (1988, in Best and Abernethy, 1994) stated that Heaviside's
dolphins are the cetaceans most frequently seen in the northern
part of their range, off the Namibian coast. In the southern portion
of the range, within a coastal area from Cape Town to 390 km north
west, 6,345 animals (95% CI = 3,573-11,267) have recently been estimated
(Elwen et al. 2009).
4. Biology and Behaviour
Habitat: As other species in the genus, it is a coastal,
shallow water animal (Jefferson et al. 1993; Reyes, 1991). Dolphins
fitted with satellite transmitters varied in their use of the inshore
areas from 39.5% to 94.7% of transmission days (38-51 total) (Elwen
et al. 2009). It is mostly seen within 8-10-km of shore and in water
less than 100 m deep. Surveys within 8 km of the coast have shown
low population densities of around 5 sightings per 160 km; sightings
dropped dramatically further offshore, and no animals were seen
in water deeper than 200 m. C. heavisidii seems to be associated
with the cold, northward-flowing Benguela Current. Some populations
may be resident year-round (Carwardine, 1995; Reyes, 1991; Rice
and Saayman, 1984). Heaviside's dolphins have been found within
a wide range of surface temperatures (9-19°C), but most sightings
(87.2%) were in water of 9-15°C (Best and Abernethy, 1994).
Behaviour: Little is known about the behaviour of this species.
It is generally undemonstrative and appears to be shy. Reactions
to vessels vary, but it is known to approach a range of boats and
to bow-ride and wake-ride; some animals have been seen "escorting"
small vessels for several hours at a time. Limited observations
suggest that at least some groups have restricted home ranges and
probably do not stray far from these areas (Carwardine, 1995).
Schooling: Heaviside's dolphins are usually found in small
groups of from one to 10 animals, with two being the most common
number. Mean group size for 149 confirmed sightings made on scientific
cruises was 3.2 animals. On some occasions two groups can be found
in close association, and it is possible that amalgamation into
larger groups may occur occasionally; the sighting of 30 animals
may represent such an occasion (Best and Abernethy, 1994 and refs.
Food: Stomach contents are available from 17 animals, and
included a minimum total of 4,928 identifiable food items. Demersal
fish such as hake (Merluccius capensis) and kingklip (Genypterus
capensis) formed 49% and octopods 22% by weight of the organisms
identified, while gobies (Sufftogobius bibarbatus) and squid
(Loligo rejnaudi) were also important components. Heaviside's
dolphin 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 (Best and Abernethy, 1994 and
Movements of this species are not well known. Repeated sightings
of individually recognisable specimens (including a pure white animal)
over a long period indicate that certain groups may be resident
in some areas (Reyes, 1991 and refs. therein). However, Best and
Abernethy (1994) concluded "whether Heaviside's dolphins reside
year-round in particular areas is an open question". An immature
male C. heavisidii marked with a spaghetti tag was recaptured
about 85 nautical miles north of the marking position. Although
little can be deduced from a single incident, this record suggests
a relatively small amount of overall movement over a 17-month period
(Best and Abernethy, 1994 and refs. therein), and a relatively wide
home range, which may easily extend across international boundaries.
Home-range estimates ranged from 302 to 1,028 km² (90% isopleths).
Although the distance from shore and depth at which individual dolphins
moved varied greatly, all dolphins showed a strong onshore-offshore
diurnal movement pattern, generally being closest inshore between
0600 h and noon, and farthest offshore between 1500 h and 0500 h.
This pattern is assumed to be related to the movements of their
principal prey, juvenile shallow-water hake (Merluccius capensis),
which migrates into the upper water column at night. Movements inshore
may be associated with rest, socializing, and predator avoidance
(Elwen et al. 2006).
Direct catch: Although fully protected legally, directed
takes with hand-thrown harpoons or guns of about 100 dolphins per
year, including Heavisides dolphin and two other species, have been
reported (Reyes, 1991 and refs. therein).
Incidental catch: Some Heaviside's dolphins become entangled
in a variety of inshore fishing nets off South Africa and Namibia
each year (Carwardine, 1995). Estimated total kills of dolphins
in 7,013 sets off Namibia in 1983 were 67 (C. heavisidii
and Lagenorhynchus obscurus combined), whereas 57 were killed
in South Africa. Other reported sources of incidental mortality
were set nets in waters close to the shore of Namibia, although
data on catch rates and mortality are lacking.
There are unconfirmed reports of specimens taken in a bottom trawl
fishery, but a drift net shark fishery does not seem to pose a threat
to the dolphin population (Reyes, 1991 and refs. therein). Heaviside's
dolphins are also known to be caught accidentally in beach-seine
nets. Up to seven dolphins have been reported to be entrapped and
beached during one net haul, and although it is likely that many
of the animals landed in this fishery are returned to the sea alive,
some mortality may occur (Best and Abernethy, 1994).
Although presently probably able to sustain mortality following
interactions with commercial fishing gear, Heaviside's dolphins
may become negatively impacted should fishing activities increase
(Peddemors, 1999; Dawson, 2009).
Deliberate culls: None reported (Reyes, 1991).
Habitat degradation: Taking into account the relatively small
home range of the species and its restricted distribution in coastal
waters, pollution and boat traffic may be causes for concern (Reyes,
Range states: Angola; Namibia; South Africa (Northern Cape Province,
Western Cape Province) (Reeves et al. 2008).
C. heavisidii is included in Appendix II of the CMS. The
species is listed as "Data Deficient" by the IUCN (Reeves
et al. 2008) . The species is listed in Appendix II of CITES.
Information on distribution and abundance is urgently needed. More
information on the nature and extent of catches is required to assess
the status of this species (Reyes, 1991). For Namibia, such data
is currently being gathered through the Namibian Dolphin Project
(Elwen, pers. comm.).
Heaviside's dolphin is protected within the 200-mile Exclusive Fishery
Zone (EFZ) of South Africa, where all delphinids are protected under
the Sea Fisheries Act of 1973. Similar protection is given In Namibia's
12-mile EFZ. Permits were formerly given for the operation of set
netting off the Namibian coast but this has been prohibited by the
Government since 1986. The main threats to the species are incidental
mortality in several fishing operations, possibly pollution and
boat traffic, and development of fisheries in the region (Reyes,
1991 and refs. therein).
Although its range is restricted to a small part of the south-western
African coast, observations by Rice and Saayman (1989) show that
relatively large groups are present regularly in waters involving
the national boundaries of Namibia and South Africa, the two known
Range States (Reyes, 1991 and refs. therein).
Further information is needed on probable distribution of the species
in Angola, whose status as a Range State needs further consideration.
More research emphasis should in future also be placed on possible
detrimental interactions due to overfishing of prey stocks. Increased
commercial fishing pressure will inevitably also increase interactions
between the fishery and Heaviside's dolphins, which are considered
to be vulnerable (Peddemors, 1999).
. Best PB, Abernethy RB (1994) Heaviside's dolphin - Cephalorhynchus
heavisdii (Gray, 1828). In: Hand-book of marine mammals (Ridgway
SH, Harrison SR, eds.) Vol. 5: The first book of dolphins. Academic
Press, London, pp. 289-310.
· Carwardine M (1995) Whales, dolphins and porpoises. Dorling
Kindersley, London, UK, 257 pp.
· Dawson SM (2009) Cephylorhynchus dolphins. In: Encyclopedia
of marine mammals (Perrin WF, Würsig B, Thewissen JGM, eds.)
Academic Press, Amsterdam, pp. 191-196.
· Elwen S, Meyer MA, Best PB, Kotze PGH, Thornton M, Swanson
S (2006) Range and movements of female heaviside's dolphins (Cephalorhychus
heavisidii), as determined by satellite-linked telemetry. J
Mammal 87: 866-877
· Elwen SH, Reeb D, Thornton M, Best PB (2009) A population
estimate of Heaviside's dolphins, Cephalorhynchus heavisidii,
at the southern end of their range. Mar Mamm Sci 25: 107-124
· Jefferson TA, Leatherwood S, Webber MA (1993) FAO Species
identification guide. Marine mammals of the world. UNEP/FAO, Rome,
· Peddemors VM (1999) Delphinids of southern Africa: A review
of their distribution, status and life history. J Cetacean Res Manage
· Reyes JC (1991) The conservation of small cetaceans: a
review. Report prepared for the Secretariat of the Convention on
the Conservation of Migratory Species of Wild Animals. UNEP / CMS
· Reeves RR, Crespo EA, Dans Jefferson TA, Karczmarski L,
Laidre K, O'Corry-Crowe G, Pedraza S, Rojas-Bracho L, Secchi ER,
Slooten E, Smith BD, Wang JY, Zhou K (2008) Cephalorhynchus heavisidii.
In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2.
· Rice DW (1998) Marine mammals of the world: systematics
and distribution. Society for Marine Mammalogy Spec Publ 4, Lawrence,
· Rice FH, Saayman GS (1984) Movements and behaviour of Heaviside's
dolphins (Cephalorhynchus heavisidii) off the western coasts
of southern Africa. Invest Cetacea 16: 49-63.
© Boris Culik (2010) Odontocetes.
The toothed whales: "Cephalorhynchus heavisidii".
UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.