Geographic Range
Cephalorhynchus heavisidii
is found in coastal waters off of Africa’s Southwestern coast, from central Angola
to the southern-most tip of South Africa. This species usually remain within 8 to
10 km of the shoreline, but has been sighted up to 45 nautical miles from the coast.
While some studies suggest that
Cephalorhynchus heavisidii
does not migrate significant distances, and that there are resident dolphins in some
areas, this is not well established. One study tracked a juvenile male that swam 158
km north of where he was tagged. Another juvenile male traveled 137 km north of his
tagging site over a 17 month period, suggesting that average daily movements might
be small. This species appears to have low population densities of around 5 individuals
per 160 km.
Habitat
Cephalorhynchus heavisidii
is found exclusively in the Atlantic Ocean. Although it is most often found in waters
less than 100 m deep, it has been sighted at depths up to 180 m. It is usually found
in waters that are between 9 and 15ÂşC, but has been found in waters as warm as 19ÂşC.
More than 87% of sightings occur in the Benguela Current.
- Habitat Regions
- tropical
- saltwater or marine
Physical Description
Adult Heaviside’s dolphins typically weigh between 60 and 70 kg, with an average body
length of 1.74 m. Maximum girth is roughly 67% of the length of the body. Each individual
has between 48 and 70 teeth. They are distinguished from other
dolphins
by their blunt head, robust body, triangular dorsal fin, and rounded paddle-like
flippers. Heaviside's dolphins have a dark gray anterior surface with a dark blue-black
patch beginning midway between the dorsal fin and the snout, and extending about halfway
down the ventral surface of the body. White markings on their underside form a three-pronged
fork, with another white rhomboidal patch on the chest and two smaller diamond-like
patches just posterior to the flippers. They also have a dark blue-black stripe, which
extends from the blowhole to the cape. Sexual dimorphism has not been reported in
this species.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
Reproduction
There is no information available regarding the mating system of Heaviside's dolphins.
However,
bottlenose dolphins
,
spinner dolphins
, and
common dolphins
are promiscuous.
Heaviside's dolphins breed once every 2 to 4 years from spring to late summer. Gestation
lasts for 10 to 11 months. Females usually give birth to only one offspring at a time,
as there is limited space for in utero development. To account for the limited space
in the uterus, during development, the tail flukes and dorsal fins of fetuses are
cartilaginous and fold over. Newborns average 85 cm in length. Birth mass has not
been recorded for this species. However, newborn
bottlenose dolphins
range from 11.3 to 18.1 kg, and
Irrawaddy dolphins
, which average 96 cm in length at birth, has an average birth mass of 12.3 kg. There
is no information available regarding weaning and time to independence for this species.
Bottlenose dolphins
begin weaning as early as 32 months and are fully weaned by 48 months, while time
to independence ranges between 3 and 6 years. Female Heaviside's dolphins reach sexual
maturity between 5 and 9 years of age, and males reach sexual maturity between 6 and
9 years of age.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
Cephalorhynchus heavisidii
calves swim in echelon position, that is, in close proximity to the mid-lateral flank
near the dorsal fin of the mother. This allows the calf extra speed at a lower tailbeat
frequency, because it is able to ride along the pressure wave that its mother’s body
creates. However, it has been shown that this causes extra strain on the mother, who
is able to swim at only 76% of her mean maximum speed when swimming by her self. Most
dolphin calves develop strong social bonds with their mother, which remains even at
3 years of age. This extended mother-young association is thought to be due largely
to the still-improving physical performance and social skills of calves. There is
no information available regarding paternal investment in calf development.
- Parental Investment
- precocial
- female parental care
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
protecting
- female
-
provisioning
- extended period of juvenile learning
Lifespan/Longevity
There is no information available regarding the average lifespan of
Cephalorhynchus heavisidii
in captivity or in the wild. The average lifespan of most wild
delphinids
ranges from 17 to 25 years, with a few living into their early 50s. Although similar
averages are found for captive
dolphins
, few captive individuals live past their 20s. In general,
delphinids
are vulnerable to bacterial, fungal, and viral infections and have been found to
suffer from heart and respiratory disease, stomach ulcers, and even cancer.
Dolphins
are also vulnerable to a number of different parasites including
flukes
,
tapeworms
, and
roundworm
.
Behavior
Cephalorhynchus heavisidii
is diurnal and considered to be social. It is most frequently seen in groups of two
or three, but is commonly found alone or in groups of four to ten.
Cephalorhynchus heavisidii
has been documented in groups of up to 30 individuals, 10% of which generally consists
of calves.
Cephalorhynchus heavisidii
spends the early morning hours, from sunrise to midday, in inshore waters and the
remainder of its time off shore. Daily movement patterns reflect those of their prey,
particularly those of
hake
, which migrate to the top of the water column at night. Inshore movements of
dolphins
during the day are believed to be associated with resting, socializing, and predator
avoidance.
Cephalorhynchus heavisidii
often approaches boats and may swim alongside one for several hours at a time. This
species has been seen leaping up to 2 m out of the water.
- Key Behaviors
- natatorial
- diurnal
- motile
- sedentary
- social
Home Range
Heaviside’s dolphins have a home range of between 302 km^2 and 1,990km^2.
Communication and Perception
Heaviside’s dolphins communicate visually, as dolphins have exceptional underwater
vision. They also use tactile communication, swimming near other individuals and rubbing
against one another to build affiliative relationships. Acoustically, they are able
to communicate through a series of whistles and clicks ranging between 1.5 and 11.0
KHz. They communicate chemically by releasing pheromones from pores in their anal
glands. Heaviside’s dolphins also rely heavily on echolocation to perceive their surroundings.
- Other Communication Modes
- pheromones
- Perception Channels
- visual
- tactile
- acoustic
- echolocation
- chemical
Food Habits
The primary prey of
Cephalorhynchus heavisidii
includes
hake
and
kingclip
, which comprises nearly 49% of their diet.
Octopods
is also an important prey item for
C. heavisidii
, which makes up about 22% of their diet. The remainder of their diet generally consists
of
kingfish
,
gobies
, and
squid
. Dolphins have fusiform, or torpedo shaped bodies, which allows them to swim at
high speeds to avoid predation and catch prey.
- Animal Foods
- fish
- mollusks
Predation
Though
Cephalorhynchus heavisidii
is not typically vulnerable to predation, humans pose a potential threat due to by-catch.
In general,
dolphins
are subject to retaliatory killings by local fisherman and are sometimes slaughtered
for their meat, which is considered a delicacy in Japan. However, the biggest threat
to
dolphins
seems to be accidental killing. Drift fishing nets catch everything in their paths,
including dolphins, and prevent them from reaching the surface for air. It has been
estimated that drift fishing nets have killed more than 30 million
dolphins
worldwide since the 1960's.
Ecosystem Roles
Cephalorhynchus heavisidii
preys upon a number of different fish and
cephalopods
. Although this species is not a major prey item of any particular organism, body
parts of
dolphins
have been found in the gut contents of killer whales and sharks. There is no information
available regarding parasites of
Cephalorhynchus heavisidii
, nor has it been recorded to take part in any mutualistic or commensalistic relationships
with other organisms.
Economic Importance for Humans: Positive
Cephalorhynchus heavisidii
provides no known economic benefits to humans.
Economic Importance for Humans: Negative
There are no known adverse effects of Cephalorhynchus heavisidii on humans. Although local fisherman may contend that this species decreases local fish abundance, there is no documented evidence to support this.
Conservation Status
Cephalorhynchus heavisidii
is listed as “data deficient” on the IUCN Red List of Threatened Species. CITES (the
Convention on International Trade in Endangered Species of Wild Fauna and Flora) lists
Cephalorhynchus heavisidii
under Appendix II, meaning that though this species is not necessarily threatened
with extinction, its trade must be regulated so that its survival is not jeopardized.
Cephalorhynchus heavisidii
is vulnerable to harpoons and guns used by humans hunting close to shore, where about
100 are killed annually. Also, entanglement in fishing gear poses a significant threat.
In 1983, 67 were caught in nets off Namibia, and 57 off of South Africa. Although
overfishing of their primary prey may pose a threat to their survival, little evidence
exists to support this claim. As an inshore species,
C. heavisidii
is susceptible to pollution and boat traffic, and low levels of DDT have been found
in some individuals. This species is currently protected from commercial hunting and
fishing throughout its geographic range. It is also protected by a 322 km Exclusive
Fishery Zone (EFZ) off the coast of South Africa and a 20 km EFZ off the coast of
Namibia.
Other Comments
This species is sometimes referred to as Haviside's dolphin, rather than the more common Heaviside's dolphin.
Additional Links
Contributors
Samantha Blanken (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University, John Berini (editor), Animal Diversity Web Staff.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- pelagic
-
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- young precocial
-
young are relatively well-developed when born
- female parental care
-
parental care is carried out by females
- natatorial
-
specialized for swimming
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- social
-
associates with others of its species; forms social groups.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- pheromones
-
chemicals released into air or water that are detected by and responded to by other animals of the same species
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- echolocation
-
The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.
- chemical
-
uses smells or other chemicals to communicate
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
References
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