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Sousa teusziiAtlantic humpbacked dolphin

By Samantha Grasley

Geographic Range

Atlantic humpbacked dolphins live in tropical coastal waters off western Africa, from central Morocco southward to southern Angola. (Reeves, et al., 2008)

Habitat

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. ("Atlantic Hump-backed Dolphin", 2008; "Sousa teuszii", 2010)

  • Range depth
    20 to 65 m
    65.62 to 213.25 ft

Physical Description

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. ("Sousa teuszii", 2010)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    100 to 150 kg
    220.26 to 330.40 lb
  • Range length
    2.0 to 2.5 m
    6.56 to 8.20 ft
  • Range wingspan
    0 (low) mm
    0.00 (low) in
  • Average basal metabolic rate
    1200 cm3.O2/g/hr

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. ("Sousa teuszii", 2010; "Sousa teuszii", 2010)

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. ("Sousa teuszii", 2010; "The Shark Bay Dolphin Research Project", 2011)

  • 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

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. ("Sousa teuszii", 2010)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

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. ("Sousa teuszii", 2010)

  • Typical lifespan
    Status: wild
    15 to 20 hours

Behavior

Sousa teuszii is a diurnal, slow swimming species that can remain under water for up to 3 minutes at a time. This species has a large melon, which facilitates echolocation and acoustic communication between conspecifics. These dolphins are often found alone or in small groups of 3 to 7 individuals, but younger individuals are sometimes found in larger groups of 20 to 25. Group formation appears to be associated with hunting. ("Atlantic Hump-backed Dolphin, Sousa teuszii", 1998-2998)

Home Range

The average home range size of Sousa teuszii has not been documented. ("Sousa teuszii", 2010)

Communication and Perception

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. ("Distribution, behaviour, and photo-identification of Atlantic humpback dolphins Sousa teuszii off Flamingos, Angola", 2009; "Sousa teuszii", 2010)

Food Habits

The diet of Sousa teuszii consists mainly of fish, including mullet and sardines. Other important prey items include squid and crustaceans. ("Sousa teuszii", 2010)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

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. ("Sousa teuszii", 2010)

Ecosystem Roles

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. ("A review of cetacean occurence in West African waters from the Gulf of Guinea to Angola", 2010; "Conservation and management of humpback dolphins: the South African perspective", 2001; "Sousa teuszii", 2010)

Mutualist Species
  • humans, (Homo sapiens)

Economic Importance for Humans: Positive

Atlantic humpbacked dolphins benefit fisherman in Mauritania by schooling fish into shore. Local villages intentionally hunt this species for food. ("Atlantic Hump-backed Dolphin, Sousa teuszii", 1998-2998)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

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.

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. (Reeves, et al., 2008)

Other Comments

Sousa teuszii is very similar in appearance to its sister species, Sousa chinensis. Differences between these species include their geographical ranges, number of teeth, and number of vertebrae.

Contributors

Samantha Grasley (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University, John Berini (editor), Animal Diversity Web Staff.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

diurnal
  1. active during the day, 2. lasting for one day.
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.

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.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

food

A substance that provides both nutrients and energy to a living thing.

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).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

2010. A review of cetacean occurence in West African waters from the Gulf of Guinea to Angola. Mammal Review, 40/1: 2-39. Accessed April 21, 2011 at http://onlinelibrary.wiley.com.proxy1.cl.msu.edu/doi/10.1111/j.1365-2907.2009.00153.x/abstract.

2012. Activity budget of inshore Indo-Pacific bottlenose dolphins (Tursiops auduncus): A critical evalutation of methods and comparison among other populations. Marine Mammal Science, 27/1: 20-38. Accessed April 21, 2011 at http://onlinelibrary.wiley.com.proxy1.cl.msu.edu/doi/10.1111/j.1748-7692.2010.00388.x/abstract;jsessionid=DA9A67EB71C0DE514696FF41D92046B4.d03t03.

1998-2998. "Atlantic Hump-backed Dolphin, Sousa teuszii" (On-line). Marine Bio. Accessed March 14, 2011 at http://marinebio.org/species.asp?id=344.

2008. "Atlantic Hump-backed Dolphin" (On-line). Accessed March 14, 2011 at http://www.sci.tamucc.edu/~wcrc/cetaceans/world/atlantichumpbackeddolphin.html.

2001. Conservation and management of humpback dolphins: the South African perspective. Oryx, 34/3: 207-216. Accessed April 21, 2011 at http://onlinelibrary.wiley.com.proxy1.cl.msu.edu/doi/10.1046/j.1365-3008.2000.00120.x/abstract.

2009. Distribution, behaviour, and photo-identification of Atlantic humpback dolphins Sousa teuszii off Flamingos, Angola. African Journal of Marine Science, 31: 319-331.

1922. "Guide to the Whales, Porpoises, and Dolphins (Order cetacea)" (On-line). HathiTrust. Accessed March 18, 2011 at http://catalog.hathitrust.org/Record/001502709.

2010. "Sousa teuszii" (On-line). Accessed March 14, 2011 at http://www.cms.int/reports/small_cetaceans/data/S_teuszii/s_teuszii.htm.

2011. "The Shark Bay Dolphin Research Project" (On-line). Georgetown University Department of Biology. Accessed April 21, 2011 at http://biology.georgetown.edu/faculty/mann/research/.

Pauly, D. 2000. "Estimates of Basal Metabolic and Feeding Rates for Marine Mammals from Measurements of Maximum Body Length" (On-line). Accessed April 21, 2011 at http://www.marinemammal.org/pdfs/Hunter_etal2000-nutrition.pdf.

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.

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