Mammal Species of the World
Rough-toothed dolphins, Steno bredanensis have a broad geographic range which ecompasses tropical and subtropical oceans. They have been frequently sighted along various coastal areas such as Kaua’i, Ni’ihau, and O’ahu of the Hawaiian Islands, the Mediterranean Sea, the Sicily Channel, Tahiti, Moorea, and the Windward Islands.
Biogeographic Regions: nearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); oceanic islands (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )
- Gannier, A., K. West. 2005. Distribution of the rough-toothed dolphin (Steno bredanensis) around the Windward Islands. Pacific Science, 59, 1: 17-24.
- Kuczaj II, S., D. Yeater. 2007. Observations of rough-toothed dolphins (Steno bredanensis) off the coast of Utila, Honduras. Journal of the Marine Biological Association of United Kingdom, 87: 141-148.
- Ritter, F. 2007. Behavioral responses of rough-toothed dolphins to a dead newborn calf. Marine Mammal Science, 23, 2: 429-433.
- Shirihai, H., B. Jarrett. 2006. Whales, Dolphins, and other Marine Mammals of the World. Princeton, New Jersey: Princeton University Press.
- Watkins, W., P. Tyack, K. Moore, G. Notarbartolo-di-Sciara. 1987. Steno bredanensis in the Mediterranean Sea. Marine Mammal Science, 3: 78-82.
The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Worldwide in tropical and warm temperate seas; not known to be particularly numerous anywhere. Virginia to West Indies in western Atlantic; northern California to Peru in eastern Pacific (Leatherwood and Reeves 1983).
Distribution in Egypt
Red and Mediterranean Sea.
The average adult rough-toothed dolphin reaches a length of 2 to 2.65 m and a mass of 90 to 160 kg. This species is the only dolphin species that possesses a long beak. The elongated beak is dual colored; the upper jaw is blue and gray while the lower is pale pink and white. Their colorings may vary geographically. The body of rough-toothed dolphins is dark grey with white or light colored spots on their sides. The belly, lips, and parts of the lower jaw are white. Rough-toothed dolphins have a distinctive color pattern, consisting of a dark narrow cape which passes over the eyes and arches high on the sides of the body. Some of these animals show white and yellowish scars, due to encounters with large squid, cookie-cutter sharks, other rough-toothed dolphins, and interactions with boats. Males and females are similar in appearance. However, some males can grow larger and possess a more pronounced post-anal hump and prevalent scars. Rough-toothed dolphins are commonly misidentified as bottlenose dolphins, spinner dolphins, and spotted dolphins, but closer examination of the beak, head shape, and jaw color can help distinguish these species.
Range mass: 90 to 160 kg.
Range length: 2.00 to 2.65 m.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
- 1998. "Rough-toothed Dolphin" (On-line). Hebridean Whale and Dolphin Trust. Accessed March 20, 2001 at http://www.gn.apc.org/whales/dolphin8.htm.
- Carwardine, M. 1995. Whales, Dolphins and Porpoises. London: Dorling Kindersley Books.
- Jefferson, T. 2002. Rough-toothed dolphin Steno bredanensis. Pp. 1055-1059 in W Perrin, J Thewissen, B Wursig, eds. Encyclopedia of Marine Mammals, Vol. None, 1st Edition. San Diego: Academic Press.
- Kays, R., D. Wilson. 2009. Mammals of North America. Princeton, New Jersey: Princeton University Press.
- Rouch, T., S. Poss. 1998. "Species at Risk in the Gulf of Mexico Ecosystem, Steno bredanensis" (On-line). Accessed March 20, 2001 at http://lionfish.ims.usm.edu/~musweb/stenbred.htm.
Length: 280 cm
Size in North America
Range: 2-2.7 m males; 2-2.6 m females
Range: 90-155 kg
Although rough-toothed dolphins reside in both shallow and deep ocean waters, they prefer deep waters greater than 1500 m in depth. They have been found at depths of up to 2000 m. Their location is often driven by the amount of nutrients in a given area. Rough-tooth dolphins are most commonly spotted in temperate waters. They prefer sea surface temperatures of 25 ̊C during the warm season but have been discovered during the cold season in waters ranging from 17 to 24 ̊C. Rough-toothed dolphins are rarely seen ranging north of 40 degrees latitude or south of 35 degrees latitude.
Range depth: 5 to 2000 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: pelagic ; reef ; coastal
- Baird, R., D. Webster, S. Mahaffy, D. McSweeney, G. Schorr, A. Ligon. 2008. Site fidelity and association patterns in a deep-water dolphin: rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago. Marine Mammal Science, 24, 3: 535-553.
- Jefferson, T., S. Leatherwood, M. Webber. 1993. Marine Mammals of the World. Rome: Food and Agriculture Organization of the United Nations.
- West, K. 2002. Ecology and biology of the rough-toothed dolphin (Steno bredanensis). University of Hawaii Library: University of Hawaii and L'Universite' de la Polynesie Francaise.
Habitat and Ecology
Habitat Type: Marine
Comments: Tropical and warm temperate seas, especially far offshore in deep water; normally where sea surface temperature is above 25 C (Leatherwood and Reeves 1983). Sometimes associated with yellowfin tuna in eastern tropical Pacific.
Water temperature and chemistry ranges based on 411 samples.
Depth range (m): 0 - 0
Temperature range (°C): 15.689 - 29.261
Nitrate (umol/L): 0.008 - 10.051
Salinity (PPS): 31.668 - 36.431
Oxygen (ml/l): 4.491 - 5.820
Phosphate (umol/l): 0.056 - 0.897
Silicate (umol/l): 0.769 - 7.399
Temperature range (°C): 15.689 - 29.261
Nitrate (umol/L): 0.008 - 10.051
Salinity (PPS): 31.668 - 36.431
Oxygen (ml/l): 4.491 - 5.820
Phosphate (umol/l): 0.056 - 0.897
Silicate (umol/l): 0.769 - 7.399
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
The diet of carnivorous rough-toothed dolphins includes silverside, saury, needlefish, mahimahi, and squid. Their preference, however, is mahimahi. Rough-toothed dolphins are excellent divers and are known to dive to great depths in search of cephalopods and large fish. They chase their prey and toss it around with their beaks. As their common name suggests, they have rough teeth, which allow them to tear apart their prey. Rough-toothed dolphins forage in groups of 3 to 5 for predator efficiency, and they share their meals. Members of this species are also known to forage on "bait balls" of schooling fish.
Animal Foods: fish; mollusks
Primary Diet: carnivore (Piscivore , Molluscivore )
Comments: Eats pelagic octopus, squids, and various fishes (Leatherwood and Reeves 1983).
Rough-toothed dolphins help regulate adult populations of mahimahi. They also host a variety of parasites. Larvae and adult Anisakis have been found in their stomach, causing ulcers, internal bleeding, and gastritis. These nematodes may be transmitted by the sharing of food among dolphins and this parasite species' dependence upon various intermediate hosts. Several helminth parasites can also infect the intestines of rough-toothed dolphins, including the cestode Tetrabothrius forsteri. Several trematodes also parasitize rough-nosed dolphins, including Campula palliate in the liver and bile duct, Pholeter gastrophilus in the forestomach, and Synthesium tursionis in the intestines.
- Cestode Tetrabothrius forsteri
- Nematode g. Anisakis
- Trematode Campula palliate
- Trematode Pholeter gastrophilus
- Trematode Synthesium tursionis
- Carvalho, V., C. Bevilaqua, A. Iniguez, H. Mathews-Cascon, F. Ribeiro, L. Pessoa, A. Meirelles, J. Borges, J. Marigo, L. Soares, F. Silva. 2010. Metazoan parasites of cetaceans off the northeastern coast of Brazil. Veterinary Parasitology, 173: 116-122.
- Forrester, D., D. Robertson. 1975. Helminths of rough-toothed dolphins, Steno bredanensis lesson 1828, from Florida waters. The Journal of Parasitology, 61, 5: 922.
Currently, there are no known predators of rough-toothed dolphins other than humans. Although they have been found with scars from bites of cookie-cutter sharks, there is no record of this species being consumed by a shark. Rough-tooth dolphins are, however, incidentally caught in fishing nets. Some humans eat this species of dolphin.
- humans Homo sapiens
Sometimes observed in groups, usually 50 or fewer (Leatherwood and Reeves 1983); average group size was 6 in U.S. waters (see IUCN 1991). Single and mass strandings sometimes occur.
Life History and Behavior
Rough-toothed dolphins communicate with other dolphins through echolocation clicks, whistles, burst pulse signals, and synchronous swimming patterns. Echolocation clicks help provide a sense of location, directionality, and with identifying objects. Burst pulse signals, which can be heard by the human ear, can be social or reinforce echolocation functions. Whistles are used socially among dolphins. Rough-toothed dolphins often travel in a close school with either synchronous or asynchronous swimming patterns. In the group of synchronous dolphins, a single dolphin produces higher frequency echolocation calls than the rest of the group. Rough-toothed dolphins are also found traveling alone, and these dolphins produce lower frequency echolocation calls.
Communication Channels: tactile ; acoustic
Perception Channels: tactile ; acoustic ; ultrasound ; echolocation ; chemical
Rough-toothed dolphins off the coast of Japan can live to be 32 to 36 years of age, though it is presumed that members of this species may live considerably longer. The oldest individual was estimated to be 48 years old and was found stranded from the Florida coast. The longest lived individual in captivity, however, was only 12 years of age.
Status: wild: 32 to 48 years.
Status: captivity: 12 (high) years.
Status: wild: 32.0 years.
Lifespan, longevity, and ageing
Little information is available regarding the mating systems of rough-toothed dolphins in the wild.
The reproductive habits of rough-toothed dolphins are not well known, though captive studies provide some information. At birth, rough-toothed dolphins measure 1 to 1.3 m in length. Calves attempt to nurse within an hour of birth, but are initially unsuccessful, unable to connect to their mother’s mammary slits. Within the first 3 days, calves can successfully nurse, which takes place underwater and occurs throughout the day. Calves nurse, rest, and play on a daily basis. Play time generally follows nursing and includes exploration to the surface while staying in close proximity to the mother. Calves rest around midday for about 60 minutes. At 2 months of age, calves begin to eat fish and decrease nursing time.
Rough-toothed dolphins exhibit sexual dimorphism, and mature males are longer than mature females. In both sexes, the most rapid growth occurs in the first 5 years. Females reach sexual maturity at 9 to 10 years of age at a length of 212 to 217 cm and a weight of 101 to 108 kg. Males reach sexual maturity at 5 to 10 years of age at a length of about 216 cm and a weight of 92 to 102 kg.
Range weaning age: 2 (low) months.
Range age at sexual or reproductive maturity (female): 9 to 10 years.
Range age at sexual or reproductive maturity (male): 5 to 10 years.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
In captivity, female rough-toothed dolphins protect their calves by swimming in close proximity to their young and positioning themselves between the calf and other dolphins. The length of the mother-calf relationship is unknown. A female rough-toothed dolphin, presumed to be the mother, was observed supporting a dead calf at water's surface for several days. During this time, she was escorted and protected by a number of male rough-toothed dolphins. This may demonstrate a prolonged mother-calf association in rough-toothed dolphins. Such behavior has been observed in the tight social groups of other marine mammals.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female); pre-independence (Provisioning: Female)
In the western North Pacific, average age of mature males was 14 years, average age of mature females was 10 years; maximum age 30-32 years (see IUCN 1991).
Molecular Biology and Genetics
Barcode data: Steno bredanensis
Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen.
Other sequences that do not yet meet barcode criteria may also be available.
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Download FASTA File
Statistics of barcoding coverage: Steno bredanensis
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
Although listed as a species of list concern on the ICUN Red List, Steno bredanensis is experiencing an increase in mortality rate. Fisheries along the coast of Ceara, Brazil incidentally catch rough-toothed dolphins in gill nets. Individuals caught in gill nets are thrown overboard or used as bait for sharks. Small numbers of rough-toothed dolphins are targeted as food for humans by direct and drive fisheries, located in the West Indies, West Africa, Japan, and the Solomon Islands. Habitat destruction due to anthropogenic disturbances also threaten populations of this species.
Severe to profound hearing loss was found in 5 out of 14 rough-toothed dolphins stranded or entangled in fishing gear from 2004-2009. Hearing loss in marine mammals is contributed to five factors: congenital genetic factors, intense chronic noise from boats, old age, intense noises such as explosions, and ototoxic drug treatments that are administered during rehabilitation from dolphin strands. Hearing loss in 2 out of the 5 rough-toothed dolphins affected was contributed to genetic factors because they were young dolphins.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
- Mann, D., M. Hill-Cook, C. Manire, D. Greenhow, E. Montie, J. Powell, R. Wells, G. Bauer, P. Cunningham-Smith, R. Lingenfelser, R. DiGiovanni, A. Stone, M. Brodsky, R. Stevens, G. Kieffer, P. Hoetjes. 2010. Hearing loss in stranded odontocete dolphins and whales. PLoS ONE, 5 (11) e 13824: 1-5.
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Data Deficient
- 1994Insufficiently Known(Groombridge 1994)
National NatureServe Conservation Status
Rounded National Status Rank: NU - Unrankable
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Status in Egypt
A few Rough-toothed Dolphins are killed incidentally in tuna purse seines in the eastern tropical Pacific: 21 were estimated killed during the period 1971-75 and 36 died in a single net haul in 1982. Small numbers are also taken as by-catch in gillnet and driftnet fisheries in Sri Lanka, Brazil, the central North Pacific and probably elsewhere around the world in tropical and warm-temperate waters (Miyazaki and Perrin 1994). Monteiro-Neto et al. (2000) reported on fishery-related mortality along the coast of Ceara State, northeast Brazil, commenting on the possible conservation implications for the local subpopulations. Seasonally, incidental catches were more frequent during the austral spring (October-December). Rough-toothed Dolphins are also taken by gill nets, driftnets and pelagic long-lines in Taiwan (J. Wang pers. comm.).
Comments: Apparently not taken in large numbers incidental to fisheries, though the level of incidental take in pelagic driftnet fisheries is unknown (IUCN 1991). More information on population size and incidental and direct harvest is needed.
The biology, life history, population size, and separation into subpopulations, as well as migratory behaviour are insufficiently known. Research on this species should be encouraged.
Relevance to Humans and Ecosystems
There are no known adverse effects of rough-toothed dolphins on humans.
Steno bredanensis individuals are caught and consumed by humans in the West Indies, West Africa, Japan, and the Solomon Islands.
Positive Impacts: food
Comments: Small numbers are taken for human consumption in the western and southwestern Pacific and West Africa (IUCN 1991). Has been kept successfully in captivity for display purposes (Tomich 1986).
IUCN Red List Category
The rough-toothed dolphin (Steno bredanensis) is a species of dolphin that can be found in deep warm and tropical waters around the world.
The species was first described by Georges Cuvier in 1823. The genus name Steno, of which this species is the only member, comes from the Greek for 'narrow', referring to the animal's beak — which is a diagnostic characteristic of the species. The specific name honours van Breda, who studied Cuvier's writings. There are no recognised subspecies.
The rough-toothed dolphin is a relatively large species, with adults ranging from 2.09 to 2.83 metres (6.9 to 9.3 ft) in length, and weighing between 90 and 155 kilograms (198 and 342 lb); males are larger than females. Its most visible characteristic feature is its conical head and slender nose; other dolphins either have a shorter snout or a more visibly bulging melon on the forehead. As the common name for the species implies, the teeth are also distinctive, having a roughened surface formed by numerous narrow irregular ridges. They have been reported to have between nineteen and twenty-eight teeth in each quarter of the jaw.
The flippers are set back further along the body than in other similar dolphins, although, at sea this dolphin may be confused with spinner, spotted and bottlenose dolphins. The dorsal fin is pronounced, being from 18 to 28 centimetres (7.1 to 11.0 in) in height. The animal's flanks are a light gray, while the back and dorsal fin are a much darker gray. Older individuals often have distinctive pinkish, yellow, or white markings around the mouth and along the underside.
Population and distribution
The distribution and population of the Rough-toothed Dolphin is poorly understood. They inhabit the Pacific, Atlantic, and Indian Oceans, and in the Mediterranean Sea, in warm temperate to tropical waters, with occasional reports from cooler environments. Live sightings are almost universally made far off-shore, beyond the continental shelf, in water at least 1 kilometre (0.62 mi) deep.
Most of the research activity concerning the dolphin has been directed in the eastern Pacific, where a population estimate of 150,000 has been obtained.[by whom?] Fossils belonging to the genus Steno are known from Europe and date to the early to mid Pliocene.
Behaviour and diet
Rough-toothed dolphins are typically social animals, although solitary individuals are also sighted. An average group has between ten and twenty members, but they can vary from as few as two to as many as ninety. Such groups are thought to be temporary assemblages, composed of smaller, more permanent groups of two to eight closely related individuals that occasionally join together with others. They have also been reported to school together with other species of dolphin, and with pilot whales, false killer whales, and humpback whales.
Rough-toothed dolphins have been reported to bow-ride on a number of occasions, although apparently they do not do so as frequently as many other dolphin species. They do, however, commonly "skim", by swimming with their heads and chin above the surface of the water. They are known to be able to dive to at least 50 metres (160 ft) and be able to stay underwater for at least fifteen minutes. Their echolocation clicks are unusually brief, lasting no more than 0.2 seconds, and have a relatively low frequency, ranging from 2.7 to 256 kHz, with a maximum peak frequency of 25 kHz. They also make longer whistles with a frequency between 3 and 12 kHz.
Although details of their diet are sketchy, the stomach contents of stranded dolphins have included such fish such as silversides, sauries, houndfish, smelts, cutlassfish, and various squid and octopuses. Predators on rough-toothed dolphins are thought to include killer whales and sharks.
Rough-toothed dolphins give birth to a single young, after an unknown period of gestation; it is also unknown whether or not they have a distinct breeding season. The young are about 100 centimetres (39 in) long at birth, and grow rapidly for the first five years of life. Females reach sexual maturity somewhere between six and ten years of age, and males between five and ten years.
The population is not believed to be threatened by human activities. A small number of individuals have been harpooned by Japanese whalers. Others have been caught in seine nets by trawlers fishing for tuna. They adapt well to captivity and have proven to be intelligent and creative. Less than a dozen rough-toothed dolphins live in dolphinaria around the world. The Rough-toothed dolphin is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS) and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU) and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU)
- Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). "Steno bredanensis". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 January 2013.
- West, K.L. et al. (2011). "Steno bredanensis (Cetacea: Delphinidae)". Mammalian Species 43 (1): 177–189. doi:10.1644/886.1.
- Gannier, A. & West, K.L. (2005). "Distribution of the rough-toothed dolphin (Steno bredanensis) around the Windward Islands (French Polynesia)". Pacific Science 59 (1): 17–24. doi:10.1353/psc.2005.0007.
- Baird, R.W. et al. (2008). "Site fidelity and association patterns in a deep-water dolphin: Rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago". Marine Mammal Science 24 (3): 535–663. doi:10.1111/j.1748-7692.2008.00201.x.
- Ritter, F. (2002). "Behavioral observations of rough-toothed dolphins (Steno bredanensis) off La Gomera, Canary Islands (1995–2000), with special reference to their interactions with humans". Aquatic Mammals 28 (1): 46–59.
- Kuczaj, S.A. & Yeater, D.B. (2007). "Observations of rough-toothed dolphins (Steno bredanensis) off the coast of Utila, Honduras". Journal of the Marine Biological Association of the United Kingdom 87 (1): 141–148. doi:10.1017/S0025315407054999.
- Watkins, W.A. et al. (1987). "Steno bredanensis in the Mediterranean Sea". Marine Mammal Science 3 (1): 78–82. doi:10.1111/j.1748-7692.1987.tb00152.x.
- Siciliano, S. et al. (2007). "Age and growth of some delphinids in south-eastern Brazil". Journal of the Marine Biological Association of the United Kingdom 87 (1): 293–303. doi:10.1017/S0025315407053398.
- Steno bredanensis pp. 269–280, by J Maigret in Handbuch der Säugetiere Europas. Band 6: Meeressäuger Teil 1A: Wale und Delphine 1 Niethammer J, Krapp F, (Eds.) (1995).
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