Sousa teuszii

Geographic Range

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

• Biogeographic Regions
• ethiopian ethiopian
• atlantic ocean atlantic ocean
  • native native

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.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• reef reef
• rivers and streams
• coastal coastal

• Other Habitat Features
• estuarine estuarine

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

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 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.

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

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.

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.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary
• social social

Home Range

The average home range size of Sousa teuszii has not been documented.

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.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• echolocation echolocation
• chemical chemical

Food Habits

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

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• 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.

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.

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.

• Positive Impacts
• food 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.

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.

Additional Links

Encyclopedia of Life

Contributors

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

References

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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 .

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/ .