The rough-toothed dolphin (''Steno bredanensis'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of dolphin that can be found in deep warm and tropical waters around the world. The species was first described by

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

in 1823. The genus name ''Steno'', of which this species is the only member, comes from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

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 In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

Taxonomy

This species was formerly classified in the now-defunct subfamily Stenoninae, but more recent evidence has found that, despite its prominent bill, it in fact belongs with the blunt-nosed dolphins in the subfamily

Globicephalinae Globicephalinae is a subfamily of oceanic dolphins that includes the pilot whales (''Globicephala'' spp.), the pygmy killer whale (''Feresa attenuata''), the rough-toothed dolphin (''Steno bredanensis''), the false killer whale (''Pseudorca crass ...

Description

The rough-toothed dolphin is a relatively large species, with adults ranging from in length, and weighing between ; 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 A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. It can also specifically refer to ''Cucumis melo'', commonly known as the "true melon" or simply "melon". The term "melon" can apply to both the p ...

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 rough-toothed dolphins jaw on the outside is very distinct. The color of the lower jaw is usually white, but can have a hint of pink mixed in. The flippers are set back further along the body than in other similar dolphins, although, at sea this dolphin may be confused with

spinner Spinner may refer to: Technology * Spinner (aeronautics), the aerodynamic cone at the hub of an aircraft propeller * Spinner (cell culture), laboratory equipment for cultivating plant or mammalian cells * Spinner (computing), a graphical widget in ...

, spotted and

bottlenose dolphin The bottlenose dolphin is a toothed whale in the genus ''Tursiops''. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bot ...

s. The

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

is pronounced, being from 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 The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

, and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

s, and in the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, in warm temperate to tropical waters, with occasional reports from cooler environments. Rough-toothed dolphins can also be seen regularly in locations stretching from the

Windward Islands The Windward Islands are the southern, generally larger islands of the Lesser Antilles of the Caribbean islands or the West Indies. Located approximately between latitudes 10° and 16° N and longitudes 60° and 62° W, they extend from D ...

Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

, but only a small handful have been seen in

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

and

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

. Live sightings are almost universally made far off-shore, beyond the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

, in water at least deep. Most of the research activity concerning the dolphin has been directed in the eastern Pacific, where a population estimate of 150,000 was obtained by researchers in the 1980s. Fossils belonging to the genus ''Steno'' are known from Europe and date to the early to mid-

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 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 with others. They have also been reported to school together with other species of dolphin, and with

pilot whale Pilot whales are cetaceans belonging to the genus ''Globicephala''. The two Extant taxon, extant species are the long-finned pilot whale (''G. melas'') and the short-finned pilot whale (''G. macrorhynchus''). The two are not readily distinguish ...

false killer whale The false killer whale (''Pseudorca crassidens'') is a species of oceanic dolphin that is the only extant representative of the genus ''Pseudorca''. It is found in oceans worldwide but mainly in tropical regions. It was first species descriptio ...

s, and

humpback whale The humpback whale (''Megaptera novaeangliae'') is a species of baleen whale. It is a rorqual (a member of the family Balaenopteridae) and is the monotypic taxon, only species in the genus ''Megaptera''. Adults range in length from and weigh u ...

s. 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 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 The houndfish, or more specifically the crocodile needlefish (''Tylosurus crocodilus'') is a game fish of the family Belonidae, the needlefishes. It is the largest member of its family, growing up to in length and in weight. Taxonomy The houndf ...

smelts Smelts are a family of small fish, the Osmeridae, found in the North Atlantic and North Pacific oceans, as well as rivers, streams and lakes in Europe, North America and Northeast Asia. They are also known as freshwater smelts or typical smelts ...

cutlassfish The cutlassfishes are about 45 species of predatory ray-finned fish in the family Trichiuridae of the order Scombriformes found in seas throughout the world. Fish of this family are long, slender, and generally steely blue or silver in colour, ...

, and various

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

and

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

es. Predators on rough-toothed dolphins are thought to include

killer whale The orca (''Orcinus orca''), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus '' Orcinus'', it is recognizable by its black-and-white-patterned body. A cosmopolit ...

s and

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

s. Rough-toothed dolphins have controversially been reported to engage in intentional self-intoxication with

puffer fish Tetraodontidae is a family of marine and freshwater fish in the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowers, blowies, bubblefish, globefish, swellfish, ...

toxins.

Reproduction

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 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.

Conservation

The population is not believed to be threatened by human activities. A small number of individuals have been

harpoon A harpoon is a long, spear-like projectile used in fishing, whaling, sealing, and other hunting to shoot, kill, and capture large fish or marine mammals such as seals, sea cows, and whales. It impales the target and secures it with barb or ...

ed by Japanese whalers and pods are also slaughtered in the Taiji drive hunts. Others have been caught in seine nets by trawlers fishing for

tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...

. 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 Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas, often abbreviated to ASCOBANS, is a regional agreement on the protection of small cetaceans that was concluded as the Agreement on the Con ...

) 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). There are two rough toothed dolphins located at the

Clearwater Marine Aquarium Clearwater Marine Aquarium is a 501(c)(3) non-profit organization, and aquarium in Clearwater, Florida. It is dedicated to the rescue, rehabilitation and release of sick and injured marine animals, public education, conservation, and research. ...

. The facility is one of two that houses the species, in North America.

Taxonomy

Description

Population and distribution

Reproduction

Conservation

See also

References

Further reading