Heaviside's dolphin (''Cephalorhynchus heavisidii'')
is one of four
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s in the genus ''
Cephalorhynchus
''Cephalorhynchus'' is a genus in the dolphin family Delphinidae.
Extant species
It consists of four species:
The species have similar physical features—they are small, generally playful, blunt-nosed dolphins—but they are found in di ...
''. The small
cetacean is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
to the
Benguela ecosystem along the southwest coast of
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
.
Taxonomy and evolution
Nomenclature
Early in the 19th century, a specimen was caught off the Cape of Good Hope and brought to the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
by a Captain Haviside of the
British East India Company
The East India Company (EIC) was an English, and later British, joint-stock company founded in 1600 and dissolved in 1874. It was formed to trade in the Indian Ocean region, initially with the East Indies (the Indian subcontinent and South ...
. Zoologist
John Edward Gray
John Edward Gray, FRS (12 February 1800 – 7 March 1875) was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray (1766–1828). The same is used for ...
, who described the species in his Spicilegia Zoologica,
misidentified Haviside as the surgeon
John Heaviside, whom was known for his own biological collections at the time.
"Heaviside's Dolphin" is the recognised common name, though amongst others, "Haviside's dolphin" and "Benguela dolphin" are also used, the latter especially in Namibia.
The genus name "Cephalorhynchus" comes from the Greek kephale for ‘head’ and rhynchos for ‘beak’. For the species name "heavisidii" see the above description.
Closely related species and genetic origin
The three other species in the genus Cephalorhynchus are the
Chilean dolphin
The Chilean dolphin (''Cephalorhynchus eutropia''), also known as the black dolphin, is one of four dolphins in the genus ''Cephalorhynchus''. The dolphin is found only off the coast of Chile; it is commonly referred to in the country as ''ton ...
(''C. eutropia''), the
Commerson's dolphin
Commerson's dolphin (''Cephalorhynchus commersonii''), also referred to by the common names jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina overa (in South America), is a small oceanic dolphin of the genus ''Cephalorhynchus'' ...
(''C. commersonii'') and the
Hector's dolphin
Hector's dolphin (''Cephalorhynchus hectori'') is one of four dolphin species belonging to the genus '' Cephalorhynchus''. Hector's dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: ''C. h. hectori'', the more n ...
(''C. hectori''). All are located in cool temperate shelf waters in the
Southern Hemisphere.
Genetic studies suggest that the ''Cephalorhynchus'' dolphins originated from a single common ancestor in
Southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number o ...
, from which Heaviside's dolphin are the basal species.
Radiation around the southern hemisphere following the
Antarctic Circumpolar Current (otherwise known as the West Wind Drift), first to
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
and then to
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
, is thought to have led to the subsequent speciation within the genus.
Description
Morphology
Heaviside's are small and stocky with adults reaching a maximum length and weight of 1.7m and 75 kg 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
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
are coloured light grey with darker patches around the eye. The
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...
,
fluke and dorsal cape are a dark grey to almost black with a band that extends forward from the
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...
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
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...
and a single white patch extends between these fins on the chest.
Sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
is minimal, however variation in the shape of the white patch covering the genital slit is distinct between genders. In males, the patch ends in a point, but in females widens out to cover the mammary slits.
Life history
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.
Group size
Typically occurs in small groups of 2–3, but numbers of 1-10 are frequent and large aggregations of ~100 individuals or more are known to form in high density areas.
Nursery groups (exclusively females and calves) are not formed in this species.
Predation
Levels of predation are unknown, however
killer whale
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white ...
s (Orcinus orca) are known predators and there is evidence of shark attack from body scars.
Distribution
Geographic range
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
Cape Point ( af, Kaappunt) is a promontory at the southeast corner of the Cape Peninsula, a mountainous and scenic landform that runs north-south for about thirty kilometres at the extreme southwestern tip of the African continent in South Af ...
, the real southern limit beyond which sightings are extremely rare is Hout Bay, some 40 km 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 to the north of this along the South African coast, through
Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
and into southern
Angola
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where the northern boundary for the species remains poorly defined. Several dolphins have been sighted or accidentally caught by fishing vessels north of the Angola-Namibia border,
but no sightings were reported during a series of coastal scientific surveys at Tombua which is approximately 170 km into Angola but well south of the defined northern boundary of the Benguela Ecosystem. The northern boundary of the Benguela current shifts north and south seasonally and as Heaviside's dolphins appear closely linked to its cool waters, their northern range limit may shift along with water conditions.
Systematic surveys have dedicated effort to describing the distribution in southern
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
and current research efforts focus on local populations in
Walvis Bay
Walvis Bay ( en, lit. Whale Bay; af, Walvisbaai; ger, Walfischbucht or Walfischbai) is a city in Namibia and the name of the bay on which it lies. It is the second largest city in Namibia and the largest coastal city in the country. The ci ...
and
Lüderitz
Lüderitz is a town in the ǁKaras Region of southern Namibia. It lies on one of the least hospitable coasts in Africa. It is a port developed around Robert Harbour and Shark Island.
The town is known for its colonial architecture, includ ...
,
Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
.
These locations are also popular hotspots for watching these dolphins in addition to
Table Bay
Table Bay (Afrikaans: ''Tafelbaai'') is a natural bay on the Atlantic Ocean overlooked by Cape Town (founded 1652 by Van Riebeeck) and is at the northern end of the Cape Peninsula, which stretches south to the Cape of Good Hope. It was named b ...
(
Cape Town
Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second largest ...
) and
Britannia Bay,
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
. Sightings are common from land and there are several dolphin watching tour companies by which Heaviside's dolphins can be seen by boat.
Recent genetic research has demonstrated evidence of population structure across the range, indicating two metapopulations (north and south) with limited genetic exchange.
This pattern of fragmentation is a common feature amongst the other three species in the genus ''Cephalorhynchus'' and most prevalent in the
Hector's dolphin
Hector's dolphin (''Cephalorhynchus hectori'') is one of four dolphin species belonging to the genus '' Cephalorhynchus''. Hector's dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: ''C. h. hectori'', the more n ...
, which displays genetic isolation over very short distances.
Habitat preferences
Heaviside's dolphins typically remain nearshore in the mornings where they typically socialise and rest. When nearshore their distribution patterns are remarkably predictable within and between years, with the animals showing highly consistent use of aggregation sites at the exposed western tips of most bays throughout South Africa and Namibia, but they are rarely seen in the protected shallows of these bays. Outside of bays, they show relatively high densities along exposed sandy beaches, but these may be a secondary choice after a preference for areas where there is a high abundance of their main prey item; juvenile hake (''Merluccius capensis'') in adjacent offshore waters. Most commonly sighted within sea surface temperatures of and depths less than .
Behaviour
Heaviside's dolphins are energetic and social animals, especially when nearshore in the mornings Behaviour when offshore tends to be less playful an may include a rest phase when moving offshore to feed. They are attracted to boats and frequently bow-ride.
Individuals can also be seen surfing in coastal waves. Iconic vertical leaps clear the water before re-entering headfirst with almost no splash.
Heaviside's dolphins use echolocation to find and capture prey.
Mating typically occurs in social groups of 3-7 individuals which remain in a small area exhibiting extensive rolling, touching and position changes with frequent leaps by one of pairs of animals which potentially serve a competitive function.
Diet and Foraging
Prey items consist of mostly
demersal fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
and
cephalopod species, predominantly juvenile hake (''Merluccius capensis'') and octopus, however
pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...
species such as juvenile goby (''Sufflogobius bibarbatus'') and horse mackerel (''Trachurus trachurus capensis'') are also consumed especially in Namibia.
Foraging occurs mostly at the seabed, in shallow depths. Feeding nearshore is rarely observed.
Movement patterns
A
diurnal movement pattern is present in
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
, whereby the
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s move offshore in the afternoon to feed on prey rising vertically to the surface at night.
Movement inshore to rest and socialise occurs in the morning.
However, the pattern is different in Luderitz and Walvis Bay, Namibia where the movement is less pronounced and dolphins appear to stay inshore during the night, which is likely associated with foraging on different prey.
Home range and site fidelity
Heaviside's have small home ranges of 50–80 km as measured using satellite telemetry over 2–3 months and photographic resightings over up to 3 years.
Some individuals have been resighted at the same location for up to 10 years.
Dive time and depth
There has been limited research into Heaviside's diving behaviour, however a study of two dolphins fitted with satellite tags was undertaken in South Africa in 1997.
The maximum dive depth recorded was 147 meters, however the majority of dives were less than 50 meters.
Dive duration were predominantly less than 2 minutes with most dives between 0 and 1 minutes (Davis et al. 2014).
Sympatry with other delphinids
Whilst typically found further from shore,
dusky dolphin
The dusky dolphin (''Lagenorhynchus obscurus'') is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, b ...
s (''Lagenorhynchus obscurus'') are found throughout the range and occasionally both dolphin species are sighted in mixed groups.
Where both species overlap in prey selection, Heaviside's take larger prey items, potentially because they are outcompeted by the larger dusky dolphins for their preferred, smaller sized prey.
In central Namibia (especially Walvis Bay) Heaviside's dolphins overlap with a small populations of fewer than 100 common bottlenose dolphins REF. The bottlenose dolphin population use only wter less than 15m depth while in this area Heaviside's dolphins are almost always envounteres in water deeper than 20m, suggetsing some form of competitive exclusion.
Vocalisations
As is the case with all species in the genus, Heaviside's dolphins produce narrow-band high-frequency (NBHF) echolocation clicks (centred around 125–130 kHz), and do not whistle.
This adaptation is theorised to allow acoustic crypsis from eavesdropping predators, as the sounds produced are outside of the detectable frequencies of killer whales.
Although NBHF clicks are limited in acoustic range, they have a better resolution for small targets and are thought to provide a foraging advantage in the often cluttered, nearshore environment in which these species occur.
Heaviside's also produce a second click type, of lower frequency and broader bandwidth, that is within the hearing range of killer whales.
These calls are produced most frequently in groups engaging in social behaviour. It is likely that the dolphins use these calls when socialising away from predator threat and switch to high frequency clicks when foraging and travelling.
Population status
No total
abundance
Abundance may refer to:
In science and technology
* Abundance (economics), the opposite of scarcities
* Abundance (ecology), the relative representation of a species in a community
* Abundance (programming language), a Forth-like computer prog ...
estimate currently exists, however a population estimate of 6,345 for the region between
Table Bay
Table Bay (Afrikaans: ''Tafelbaai'') is a natural bay on the Atlantic Ocean overlooked by Cape Town (founded 1652 by Van Riebeeck) and is at the northern end of the Cape Peninsula, which stretches south to the Cape of Good Hope. It was named b ...
and
Lamberts Bay
Lambert's Bay is a small fishing town in the Western Cape province of South Africa situated north of Cape Town. It is part of the Cederberg Municipality.
The coast town has been proclaimed 'the Diamond of the West Coast' because of its white bea ...
, South Africa represents the southernmost populations in the species range.
Local population estimates for
Walvis bay
Walvis Bay ( en, lit. Whale Bay; af, Walvisbaai; ger, Walfischbucht or Walfischbai) is a city in Namibia and the name of the bay on which it lies. It is the second largest city in Namibia and the largest coastal city in the country. The ci ...
and
Lüderitz
Lüderitz is a town in the ǁKaras Region of southern Namibia. It lies on one of the least hospitable coasts in Africa. It is a port developed around Robert Harbour and Shark Island.
The town is known for its colonial architecture, includ ...
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 of coastline along southern Namibia (REF Martin et al. 2020). Quantification of abundance throughout the range is still required.
Threats
Heaviside's dolphins are exposed to a variety of threats given their limited range in coastal shallow waters which are subject to a range of anthropogenic activities. Directed catch has occurred historically, with meat being used for human consumption.
[Best, P; Ros, G.J.B (1977). Exploitation of small cetaceans of the coast of Southern Africa. ''Report to the International Whaling Commission''27:494-497]
Bycatch and hunting
Heaviside's dolphins are exposed to several poorly quantified and rapidly changing human threats including fisheries bycatch related mortality and illegal directed catch (Elwen and Gopal, 2018; Alfaro-Shigueto et al., 2019). Recently developed mid water trawls for horse mackerel (Trachurus capensis) are considered an emerging threat.
Climate change
Heaviside's dolphins are listed amongst the cetacean species most vulnerable to climate change
as they are limited to a distribution range that includes both suitable shelf habitat and cool water temperatures (Best, 2007). The Benguela Current is the only eastern-boundary current bordered by warm-water currents at both its northern and southern limits. Consequently, small increases in water temperature could result in all shelf waters in this area becoming too warm for both species, and populations are expected to decline rather than shift poleward due to a lack of shelf habitat.
Boat interactions
Heaviside's dolphins may be exposed to increase in the marine eco-tourism business in Namibia, which has grown without regulation in Walvis Bay (Leeney, 2014). Negative effects have been demonstrated for other coastal cetacean species, for example the impact of tour boats on bottlenose dolphin behaviour in Walvis Bay includes a reduction in resting behaviour and an increase in socialising behaviour in the presence of tour boats (indurkyhua). One Heaviside's dolphin was documented in 2010 with evidence of a propeller strike along its flank. As individuals have small home ranges they may be vulnerable to localised threats.
Conservation status
Prior to 2018, the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
(IUCN) listed the Heaviside's as ‘Data Deficient’ however, as of 2017 the status was changed to ‘Near Threatened’,
owing to improved knowledge on the species from multiple studies. Despite this, the overall population trend remains unknown,
and there are many aspects of the species biology that remain to be studied
Heaviside's dolphin is listed on Appendix II of the
["Appendices I and II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS)" (PDF). 5 March 2009. p. 6. Archived from the original (PDF) on 21 February 2012.] and is included in the
Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. The Memorandum of Understanding was established in 2008 and aims to protect these species at a national, regional and global level.
References
Citations
External links
namibiandolphinproject.orguk.whales.org
{{Taxonbar, from=Q301048
Heaviside's dolphin
Cetaceans of the Atlantic Ocean
Mammals of Angola
Mammals of Namibia
Mammals of South Africa
Marine fauna of Southern Africa
Heaviside's dolphin
Heaviside's dolphin