Overview

Brief Summary

Biology

The Atlantic humpbacked dolphin is a slow swimming species, which typically moves at about five kilometres per hour, surfacing briefly every minute or so. Typically occurring in groups of four to seven individuals, the Atlantic humpbacked dolphin, unlike many other dolphins, will avoid boats and is rarely seen bow riding (2). Humpbacked dolphins are known to feed on fish, including bream, mullet and herring, and cephalopods. Off the coast of Senegal, the Atlantic humpbacked dolphin has been observed moving inshore with the incoming tide to feed on prey within mangrove channels, and then returning to the ocean as the tide retreats (2). It is thought to use echolocation when foraging; a series of clicks are produced which reflect off objects and help the dolphin locate its prey in the often murky habitat. This dolphin may also emit whistles and screams, vocalisations which may be important in communication with other dolphins (2). Very little is known about reproduction in this dolphin; breeding has been recorded in March and April, and the calves are thought to be about one metre long at birth (2).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Description

The most distinctive feature of this rather elusive cetacean is its distinctive humped appearance when it breaks the ocean's surface to breathe (2). This is caused by the wide hump or ridge on the dolphin's back, from which the dorsal fin emerges (3). The Atlantic humpbacked dolphin is a robust-bodied marine mammal (2), typically slate grey on the sides and back and light grey on the underside (3). It has a long, narrow, distinct beak (2) (3), broad flippers that are rounded at the tip, and a broad tail fin, deeply notched in the centre (2). It is thought that, like the better known and closely related Indo-Pacific humpbacked dolphin (Sousa chinensis), male Atlantic humpbacked dolphins are larger than females (2) (3).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Distribution

East Atlantic coast, from Western Sahara to Angola
translation missing: en.license_cc_by_4_0

© WoRMS for SMEBD

Source: World Register of Marine Species

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Atlantic humpbacked dolphins live in tropical coastal waters off western Africa, from central Morocco southward to southern Angola.

Biogeographic Regions: ethiopian ; atlantic ocean (Native )

  • Reeves, R., T. Collins, T. Jefferson, L. Karczmarski, K. Laidre, G. O’Corry-Crowe, L. Rojas-Bracho, E. Secchi, E. Slooten, B. Smith, J. Wang, K. Zhou. 2008. "Sousa teuszii" (On-line). The IUCN Red List of Threatened Species. Accessed July 11, 2011 at http://www.iucnredlist.org/apps/redlist/details/20425/0.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range

The Atlantic humpbacked dolphin occurs in the eastern Atlantic Ocean (1), from Western Sahara, south to southern Angola (5).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Physical Description

Morphology

Atlantic humpbacked dolphins belong to the family Delphinidae. They are gray in color with some lighter speckled markings along the ventral surface. These dolphins are characterized by, and named for, their uniquely elevated and rounded dorsal fin, which is referred to as a "hump-back." Atlantic humpbacked dolphins have a very large melon, rounded flippers, and a long pronounced beak. Adults weigh between 100 and 150 kg and are generally between 2 and 2.5 meters in length. Like most cetaceans, they have homodont dentition (i.e., no differentiation along the tooth row). A distinguishing feature of this species is the number of vertebrae, which is less than that of its sister species, Indo-Pacific humpbacked dolphins. This, along with the number of teeth (26 to 31 pairs), and the species' geographic range, help taxonomists distinguish between Atlantic humpbacked dolphins and Indo-Pacific humpbacked dolphins. Atlantic humpbacked dolphins have a basal metabolic rate of 1200 cm^3 oxygen/hour.

Range mass: 100 to 150 kg.

Range length: 2.0 to 2.5 m.

Range wingspan: 0 (low) mm.

Average basal metabolic rate: 1200 cm3.O2/g/hr.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Ecology

Habitat

In estuarine and coastal waters
translation missing: en.license_cc_by_4_0

© WoRMS for SMEBD

Source: World Register of Marine Species

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Sousa teuzii is found mostly in shallow coastal waters, rivers, and estuaries. Although typically found in shallow water, it also occurs in deeper reefs where it apparently seeks refuge from predation by killer whales. When in deeper water, this species swims mostly along the ocean floor. Sousa teuzii typically stays near the shoreline within one or two kilometers of land; it is restricted to warm tropical waters.

Range depth: 20 to 65 m.

Habitat Regions: tropical ; saltwater or marine

Aquatic Biomes: reef ; rivers and streams; coastal

Other Habitat Features: estuarine

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Shallow, tropical, coastal waters, less than 25 metres deep, are the preferred habitat of the Atlantic humpbacked dolphin. This includes the often murky waters of bays, river deltas and mangrove channels (2). This dolphin has also been observed entering large rivers, although it rarely travels far upstream, remaining within salty water (5).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Trophic Strategy

The diet of Sousa teuszii consists mainly of fish, including mullet and sardines. Other important prey items include squid and crustaceans.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Associations

As piscivores, Atlantic humpbacked dolphins likely impact the coastal fish populations of western Africa. In Mauritania, this species maintains an interesting mutualistic relationship with local fisherman. Atlantic humpbacked dolphins respond to signals sent by the fisherman to come into shore. This helps concentrate fish near the shore and allows fisherman to meet economic demands, while decreasing dolphin by-catch. There is no information available regarding parasites of this species.

Mutualist Species:

  • humans, (Homo sapiens)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Atlantic humpbacked dolphins are preyed upon during all stages of life by killer whales. In order to decrease risk of predation, they often seek cover in reefs and find refuge near shore.

Known Predators:

  • killer whales, (Orcinus orca)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Behavior

Atlantic humpbacked dolphins use echolocation to find food and communicate with conspecifics, but have relatively poor eyesight. However, its enlarged melon and high brain to body mass ratio suggest that it is well equipped for communication and perception of its immediate environment. In order to avoid predation from killer whales, Atlantic humpbacked dolphins seek shelter in coral reefs.

Communication Channels: acoustic

Perception Channels: visual ; tactile ; acoustic ; echolocation ; chemical

  • 2009. Distribution, behaviour, and photo-identification of Atlantic humpback dolphins Sousa teuszii off Flamingos, Angola. African Journal of Marine Science, 31: 319-331.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life Expectancy

The average lifespan of Atlantic humpbacked dolphins has not been documented, but based on data from other dolphins, is expected to be around 15 to 20 years.

Typical lifespan

Status: wild:
15 to 20 hours.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Reproduction

Sousa tueszii is polygynous, as a single male mates with multiple females. Calving has been reported from December to February, but may extend into other months. The exact age of sexual maturity is unknown, but most individuals reproduce between the ages of 4 and 8. The closely related Sousa chinensis breeds year round, although calves are typically born during the summer. In other dolphin species, such as Tursiops truncatus (bottlenose dolphins), mating season occurs from March through April, and calves are born between February and May. Gestation lasts for approximately 12 months and young remain close to their mother until they are about 4 or 5 years old. In Tursiops truncatus, most individuals reach sexual maturity between 5 and 12 years of age for females, and between 9 and 13 years of age for males.

Mating System: polygynous

Little information exists regarding the reproductive behavior of Sousa tueszii. Calving has been reported from December to February, but may extend into other months. The exact age of sexual maturity is unknown, but most individuals reproduce between the ages of 4 and 8. Sousa tueszii has an average of one offspring per cycle, which weighs between 9 and 11 kg. Weaning has been reported in individuals as young as 24 months but usually is completed by 48 months. In the closely related Sousa chinensis, males often court females by somersaulting, chasing them in circles, and waving their flippers. In other dolphin species, such as Tursiops truncatus, males aggressively engage females during mating season and use a social hierarchy system based on size to determine which individuals mate.

Breeding interval: Sousa tueszii breeds once yearly.

Breeding season: Sousa tueszii breeds during April or May.

Average number of offspring: 1.

Average gestation period: 12 months.

Range weaning age: 24 (low) months.

Average weaning age: 48 months.

Range time to independence: 4 to 5 years.

Range age at sexual or reproductive maturity (female): 4 to 7 years.

Range age at sexual or reproductive maturity (male): 4 to 7 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

There is no information available regarding parental care in Sousa teuszii. In other dolphin species, such as Tursiops truncatus and the closely related Sousa chinensus, gestation lasts for approximately 12 months. In these species, calves become completely independent when they are approximately 4 to 5 years old. Until the calf reaches sexual maturity, it remains close to the mother.

Parental Investment: pre-hatching/birth (Provisioning: Female, Protecting: Female)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Conservation Status

Sousa teuszii is classified as vulnerable on the IUCN's Red List of Threatened Species. Major threats include hunting/whaling, entanglement in fishing nets, habitat destruction, and pollution. This species is listed under Appendix I of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) and appears to be especially vulnerable to population decrease due to its small and fragmented range and its narrow ecological niche.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: vulnerable

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Status

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix I of CITES (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Threats

As an inhabitant of coastal waters, the Atlantic humpbacked dolphin is highly vulnerable to the effects of human activities (2). Fisheries impact the dolphin, firstly, by causing incidental mortality when the dolphin becomes entangled in fishing gear (6). This is currently considered to be the greatest immediate threat to this species (1), and may be the reason behind the rarity of this species in the coastal waters of Senegal and Gambia, and in Dakhla Bay in Western Sahara, two areas in which the Atlantic humpbacked dolphin was once common (6). Secondly, fisheries may impact this dolphin by reducing the availability of prey (6). In certain areas, the Atlantic humpbacked dolphin is also captured intentionally for food by local people (5), although the numbers that are caught, and what impact this has on the population, is not known (1). In addition to the threat of fisheries, the Atlantic humpbacked dolphin is potentially being affected by boat strikes and habitat degradation. For example, mangroves are being converted to rice cultivation in some areas, destroying an important foraging habitat of this dolphin (1) (5). A high human population density within its range, and the associated development of agriculture and industry, will undoubtedly continue to have an impact on the shallow coastal waters in which the Atlantic humpbacked dolphin is found (1) (5).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management

Conservation

The Atlantic humpbacked dolphin is listed on Appendix II of the Convention on Migratory Species (CMS). This indicates that this is a species that would benefit from international co-operation, with regards to its conservation, and the Convention encourages the relevant countries to implement suitable conservation measures (7). Considering its specific habitat preferences, estimated low abundance and the threats it faces, the Atlantic humpbacked dolphin is likely to be in great need of further research and conservation measures (6).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

Although there are no known adverse effects of Sousa teuszii on humans, it is thought that this species competes with local fisherman for fish off the west coast of Africa.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Atlantic humpbacked dolphins benefit fisherman in Mauritania by schooling fish into shore. Local villages intentionally hunt this species for food.

Positive Impacts: food

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Risks

IUCN Red List Category

Vulnerable (VU)
translation missing: en.license_cc_by_4_0

© WoRMS for SMEBD

Source: World Register of Marine Species

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!