Atlantic humpbacked dolphin
Sousa teuszii © Würtz-Artescienza
The Atlantic humpbacked dolphin (Sousa teuszii) is a marine mammal within the family of Oceanic Dolphins, part of the order of cetaceans. Owing to the volatile political and military atmosphere in Angola and other parts of Western Africa, zoologists have not had an opportunity to thoroughly examine Sousa teuszii. Because of this, many characteristics of the dolphin are based on few studied individuals. As its name implies, the Atlantic hump-backed dolphin is most well known for its unusually shaped dorsal fin that gives it its hump-backed appearance. This dolphin is a sister species to the Indo-Pacific humpbacked dolphin (Sousa chinensis).
 Atlantic humpback dolphins (Sousa teuszii) just outside the surf in West Africa. Source: Tim Collins, Wildlife Conservation Society
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Conservation Status |
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Scientific Classification Kingdom: Animalia (Animals) |
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Common names Atlantic hump-backed dolphin |
Contents
Physical description
The length of the Atlantic humpback dolphin is 120 to 250 centimetres (cm) from head to fluke. There is no known sexual dimorphism. The humpback dolphin is known for its unusual dorsal fin. At approximately 15 cm in height, the dorsal fin is curved, as it is in most dolphins, however, instead of coming back directly to the dolphins back-side, the fin projects upward once again to create a "hump" behind the fin. A second, smaller hump, exists on the dorsal side just prior to the fluke.Sousa teuszii's pectoral fins are under 30 cm in length, and their flukes have a width of approximately 45 cm.
The coloration of Sousa teuszii darkens as individuals age. Younger dolphins are a light cream color, and as they get older, they become more gray.
Atlantic humpbacked dolphins have peg-like teeth in each jaw. They also have fewer vertebrae than their sister species. Tooth count and vertebrae, along with geographical location, are the major distinguishing characteristics between Sousa teuszii.
Reproduction
Sousa teuszii has not been thoroughly studied. Births have been recorded from December through February but may occur year-round. One offspring is born at a time. Although the age of sexual maturity is not known for the Atlantic humpback dolphin, most dolphins reach this point between the ages of four to eight years.
Behaviour
Sousa teuszii is a fairly solitary species, individuals often travel and feed alone. Groups are usually small, ranging in size from two to 10 dolphins. These dolphins are more likely to travel in groups when young and, as they get older, they then adopt a more solitary lifestyle.
Sousa teuszii is known to be slower than other Delphinidae. They may stay underwater for as much as three minutes, and when they do surface, they breathe while rolling. The Atlantic humpback dolphin is capable of leaping 120 cm out of the water.
The Atlantic humpback dolphin has some intriguing behaviour characteristics that are common to most Delphinidae. Among these characteristics is the fact that their brain to body mass ratio is higher than most other mammals, which some biologists suggest provides a prediction of intelligence. 'Sousa teuszii uses echolocation for sensory purposes. It does not rely on its sense of smell, for this sense has been lost in Delphinidae.'
While Sousa teuszii must compete for food with humans, and occasionally get stuck in fish-nets, they are a quintessential example of co-operative living among humans and animals. As stated earlier, the Atlantic humpback dolphin herds fish towards shorelines. This is beneficial to humans who wish to catch fish. A level of co-operation has developed in Mauritania where fisherman beat upon the water with sticks. Dolphins cue to this signal and begin their herding process. Fisherman are then able to capture the herded fish. As long as captured fish are in the nets, the dolphins are able to eat freely. This co-operative feeding is an example of how animals may be thought of as a partner to humans, although such practises lead to dolphin bycatch and mortality that may emperil many dolphin species.
Distribution
Sousa teuszii resides in Atlantic waters off the coast of Western Africa. The Atlantic humpback dolphin's range extends from Mauritania south to Angola. This range is the primary distinction between Sousa teuszii and its sister species Sousa chinensis, which is found in the Indian and Pacific Oceans.
Habitat
'Sousa teuszii'lives in tropical waters close to the West African shoreline. It is believed that the species does not venture more than one or two kilometres away from the shore in an effort to avoid Killer whale (Orca orcinus) predation.
Predation
Atlantic humpback dolphin (Sousa teuszii) in West Africa. Source: Mike Markovina Killler whales attempt to find'Sousa teuszii'through echolocation and it is thought by some that, by remaining close to shore,'Sousa teuszii'remains relatively safe because land disrupts the echolocating abilities of the Killer whale. When predators do actually approach, Atlantic humpack dolphins will typically seek refuge in reefs. Those dolphins that do move over deeper waters do so over sandy ocean floors.
Ecosystem roles
While'Sousa teuszii'must compete for food with humans, and occasionally become entrained in fish nets, they are a quintessential example of co-operative living among humans and animals. As stated earlier, the Atlantic humpback dolphin herds fish towards shorelines. This is beneficial to humans who wish to catch fish. A level of co-operation has developed in Mauritania where fisherman beat upon the water with sticks. Dolphins cue to this signal and begin their herding process. Fisherman are then able to capture the herded fish. While the fish are in the nets the dolphins are able to eat freely. This co-operative feeding is an example of how animals may be thought of as a partner to humans; a manner of thinking which, if accepted by more people, may lead to the conservation of many more species.
Feeding habits
Atlantic hump-backed dolphin. Source: Collection
Georges Declercq/Encyclopedia of Earth Atlantic humpback dolphins feed independently or in small groups. Their diet consists of fish such as sardines and mullet, which they herd towards land. By herding their prey close to land, they create a situation in which there is less opportunity for escape. They may also feed upon certain small crustaceans.
Conservation status
IUCN Red List: Vulnerable. The species population is declining, and faces a risk of extinction.
Threats
While'Sousa teuszii'must compete for food with humans, and occasionally get stuck in fish nets, they are a quintessential example of co-operative living among humans and animals.
References
- Michael Waters. 2010. Sousa teuszii. Encyclopedia of Life
- IUCN Red List (December, 2007) http://www.iucnredlist.org
- Ross, G.J.B. (2002) Humpback dolphins. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. Eds. Encyclopedia of Marine Mammals. Academic Press, London.
- Jefferson, T.A., Leatherwood, S. and Webber, M.A. (1993) FAO Species Identification Guide. Marine Mammals of the World. FAO, Rome.
- Van Waerebeek, K., Barnett, L., Camara, A., Cham, A., Diallo, M., Djiba, A., Jallow, A.O., Ndiaye, E., Bilal, A.S. and Bamy, I.L. (2004) Distribution, status, and biology of the Atlantic humpback dolphin, Sousa teuszii. Aquatic Mammals, 30 (1): 56 - 83.
- Reeves, R.R., Smith, B.D., Crespo, E.A. and Notarbartolo di Sciara, G. (2003) Dolphins, Whales and Porpoises: 2002–2010 Conservation Action Plan for the World's Cetaceans. IUCN/SSC Cetacean Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK.
- Convention on Migratory Species (November, 2008)
- Evans, P. 1987. The Natural History of Whales and Dolphins. New York, New York: Facts on File Publications.
- Frère, Céline H., Peter T. Hale, Lindsay Porter, Victor C. Cockcroft, and Merel L. Dalebout. 2008. Phylogenetic analysis of mtDNA sequences suggests revision of humpback dolphin (Sousa spp.) taxonomy is needed. Marine & Freshwater Research, vol. 59, no. 3. 259-268
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- IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
- Mead, James G., and Robert L. Brownell, Jr. / Wilson, Don E., and DeeAnn M. Reeder, eds. 2005. Order Cetacea. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vol. 1. 723-743
- Nowak, R. 1997. "Walker's Mammals of the World Online" (On-line). Accessed November 21, 1999
- Perrin, W. (2010). Sousa teuszii (Kükenthal, 1892). In: Perrin, W.F. World Cetacea Database. Accessed through: Perrin, W.F. World Cetacea Database
- Rice, Dale W. 1998. Marine Mammals of the World: Systematics and Distribution. Special Publications of the Society for Marine Mammals, no. 4. ix + 231
- Simmonds, M., J. Hutchinson. 1996. The Conservation of Whales and Dolphins: Science and Practice. Chinchester, England: John Wiley & Sons Ltd..
- UNESCO-IOC Register of Marine Organisms
- Van Waerebeek, Koen, Linda Barnett, Almamy Camara, Anna Cham, Mamadou Diallo, et al. 2004. Distribution, Status, and Biology of the Atlantic Humpback Dolphin, Sousa teuszii (Kükenthal, 1892). Aquatic Mammals, vol. 30, no. 1. 56-83
- Wilson, Don E., and DeeAnn M. Reeder, eds. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed., 3rd printing. xviii + 1207
- Wilson, Don E., and F. Russell Cole. 2000. Common Names of Mammals of the World. xiv + 204
This article was partially researched by a student at Texas Tech University participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. All articles have been reviewed by internal EoE editors, and by independent experts on each topic.
