Figure 122.—Spinner dolphins occur in large herds in tropical waters. As illustrated by these photos of animals off Venezuela in 1969, spinner dolphins often leap clear of the water and may come to a moving vessel from considerable distances away to frolic in its bow wave. (Photo by M. Bartlett.)
Figure 123.—A spinner dolphin jumping close beside a research vessel off the Virgin Islands. The distinctive color pattern (gray on the back, tan on the sides, and white on the belly) is clearly visible. The black-tipped rostrum and the black lips are key characters to this species. (Photo by C. McCann.)
Figure 124.—Spinner dolphins are active bow riders and may stay with a vessel for long periods of time. (Photo from off the Virgin Islands by H. E. Winn.)
Figure 125.—Although all spinner dolphins so far examined have the same basic characteristics, the degree of expression of those characteristics varies from individual to individual or area to area. These small short-snouted dolphins (those on bottom stranded near St. Petersburg, Fla. and maintained alive by the Aquatarium in that city, and those on top photographed at sea, off the northwestern Africa coast in 1972) are spinners, although their classification is uncertain. There may be several species or geographical races of spinners in the Atlantic. (Photos courtesy of W. F. Perrin [top] and Aquatarium [bottom].)
Figure 126.—A spinner dolphin harpooned in the fishery at St. Vincent, Lesser Antilles. Even after subtle aspects of the color pattern have faded, this species can be readily identified by the 46-65 teeth in both upper and lower jaws and by the distinctly black lips and black-tipped rostrum. (Photo by W. A. Huck, courtesy of Marineland of Florida.)
Euphrosyne dolphin (Stenella styx), Meyen's dolphin, blue-white dolphin, Gray's dolphin, striped porpoise, streaker porpoise.
The striped dolphin is a widely distributed relative of the spinner and the Atlantic spotted dolphins, though it more closely resembles saddleback dolphins than either of these two species. It reaches a maximum length of about 9 feet (2.7 m) and is characterized by a series of distinctive black stripes. One band of black begins near the eye and extends down the side of the body to the area of the anus. (A small secondary stripe originating with this band turns off and disappears in the white coloration of the side just above the flippers.) A second band of black extends from the eye to the flipper. Some workers have contended that striped dolphins are separable into distinct species depending on whether the eye-to-flipper stripe has one (S. coeruleoalba) or two (S. styx) components.
Most individuals have an additional distinctive finger of black coloration which extends from the black coloration behind the dorsal fin forward towards and about halfway to the eye. It is this feature which is most distinctive in animals riding the bow or leaping clear of the water. The back is dark gray to bluish gray, the sides are lighter gray, and the belly is white.
Though little is known of this species, it has been reported in herds of up to several hundred individuals and apparently exhibits behaviors very similar to those of the saddleback dolphins (p.116), frequently jumping clear of the water. Atlantic and Mediterranean animals have been reported to bow ride.
This species is most likely to be confused with the saddleback dolphin, which it closely resembles. The two may be distinguished by the following characteristics:
Striped dolphins are widely distributed in the temperate, subtropical, and tropical seas of the western North Atlantic. They have been reported from at least Halifax, Nova Scotia, south as far as Jamaica. (Additional records, purportedly from southern Greenland, involved a museum specimen. Since striped dolphins of the eastern North Atlantic are rare north of England, the species occurrence near Greenland would be highly improbable.) Individuals have recently been reported from the Gulf of Mexico.
Despite this wide distribution, striped dolphins appear to prefer warmer waters and are probably normally confined to the Gulf Stream or the waters off the continental slope. Individuals appearing to the north of the range seem to have ventured northward with fingers of warm water.
Stranded striped dolphins should be readily identifiable by the highly distinctive patterns of lateral striping discussed above for living animals. If the color pattern has faded, they may still be identified by their size, larger than other dolphin species of similar appearance, and the relatively large number of teeth (43-50 per side in both upper and lower jaws). Only the spinner dolphin, much smaller in body length and having a much longer beak, has more teeth (46-65 per side in each jaw).
Figure 127.—Despite some similarities in appearance and behavior to saddleback dolphins, striped dolphins can be readily identified by the prominent dark stripes on the side of the body. These striped dolphins were photographed between the Caribbean Islands of Curacao and Bonaire in 1972. (Photo by D. Poppe.)
Figure 128.—When they ride the bow, the most apparent characteristic of striped dolphins is usually the dark streak beginning in the black coloration behind the dorsal fin and extending forward towards but not reaching the head. This stripe is not always present, however, and the species may sometimes appear uniformly pale gray from a distance. (Photo from the tropical Atlantic by H. E. Winn.)
Figure 129.—Stranded striped dolphins. Note the distinctive black stripes 1) eye to flipper, 2) eye to anus, and 3) (on top animal) from black behind dorsal fin forward towards but not reaching the head. Some workers contend that striped dolphins are separable into two species, depending on whether the eye-to-flipper stripe has one (Stenella coeruleoalba) or two (S. styx) components. Others contend that the two belong to the same species (S. coeruleoalba). Striped dolphins have from 43 to 50 teeth in each upper and lower jaw. (Photos from Japan by W. E. Schevill [top] and from Indian Rocks Beach, Fla. by W. A. Huck, courtesy of Marineland of Florida [bottom].)
Saddleback porpoise, common dolphin, crisscross dolphin.
Saddleback dolphins reach a maximum overall length of about 8.5 feet (2.6 m) though most individuals are less than 7.5 feet (2.3 m) long. Males are slightly larger than females of the same age.
The body shape varies slightly but usually closely resembles that of the striped dolphin (p.113). The dorsal fin varies from nearly triangular to distinctly falcate and is pointed on the tip. It is sometimes all black and sometimes black on the borders with a lighter grayish region of varying size near the middle.
The back is basically black or brownish black, but this coloration and the extent of the striping patterns that form the impression of a saddle and the degree of color distinction between the different zones are highly variable.
The chest and belly are cream white to white and are the most distinctive features from a distance. Up close, the sides will be seen to be distinctly marked with an hourglass or crisscross pattern of tan or yellowish tan. This crisscross pattern is diagnostic for the species.
The rostrum is intermediate in length and shape between that of the spinner and that of the striped dolphin and is often black with a white tip.
Saddleback dolphins are often seen in herds of a thousand or more and are often very active, many animals leaping clear of the water at any time. Like spinner dolphins, saddleback dolphins are active bow-riders and often come to the boat from considerable distances. Once on the bow they often ride for extended periods of time.
Saddleback dolphins feed on squid and on a variety of fishes, including anchovies, myctophids, and hake.
Saddleback dolphins might easily be confused with striped dolphins and must be examined closely to be distinguished from them. Primary differences apparent in encounters at sea are as follows:
From a distance, saddleback dolphins might also be confused with spinner dolphins because of the habits of both species of congregating in large schools with much jumping and splashing. Both species ride the bow wave, and close examination should permit positive identification using the following characteristics:
Saddleback dolphins are widely distributed in the temperate, subtropical, and tropical waters of the western North Atlantic Ocean. They have been reported off Newfoundland, Iceland, Nova Scotia, and the coast of Massachusetts, south along the coast of North America to the Caribbean (West Indies and Jamaica), in the Gulf of Mexico, and from South American waters at least to Margarita Island, Venezuela.
The species' occurrence in the more northerly portions of this range during the summer and early fall months appears to coincide with the intrusion of warm waters into those areas. They are not uncommon off Nova Scotia in summer and fall and are casual members of the marine mammalian fauna of the remaining Maritime Provinces during that period.
In previous years, saddleback dolphins were not uncommonly encountered by collectors of Marineland of Florida working the northeast coast of Florida, but the species has been conspicuously absent since about 1960. Reasons for this apparent shift of range are unknown.
Saddleback dolphins have from 40 to 50 small, sharply pointed teeth in each side of both the upper and lower jaws. These numbers overlap with only those of the striped and spinner dolphins (with 43-50 and 46-65, respectively). Saddleback dolphins should be readily distinguishable fromboth these species by the features outlined under the descriptions of living animals and distinguishable from the bridled dolphins by the distinctive markings on the head of the two species (see Figs. 121 and 134).
Figure 130.—Saddleback dolphins captured off St. Augustine, Fla., shown in the tank at Marineland of Florida. The highly distinctive crisscross or hourglass pattern of tan or yellowish tan on the sides is clearly visible. Note also the light tip of the snout and the dark line from the center of the lower jaw to the flipper. This last characteristic readily distinguishes the saddleback dolphin from the striped dolphin, in which the black stripe begins at the corner of the mouth rather than near the center of the lower jaw. (Photos courtesy of Marineland of Florida.)
Figure 131.—Saddleback dolphins on the bow of a ship off Massachusetts in 1966. The color pattern, including the dark brownish-gray back, the crisscross pattern on the sides, and the white belly, are clearly visible. The light tip of the snout helps distinguish this species from the spinner dolphins, which have a black-tipped snout. (Photo by E. Wheeler.)
Figure 132.—The distinctive crisscross pattern of the sides of the saddleback dolphins is clearly visible even when comparatively little of the animal is seen. Note the falcate dorsal fin, which often, as here, is dark on the border, lighter near the center. (Photo by R. K. Brigham, courtesy of National Marine Fisheries Service.)
Figure 133.—Saddleback dolphins frequently jump clear of the water and may reenter in a variety of ways: 1) smoothly, head first; 2) with a chin slap; 3) with an accompanying tail lob; or 4) on the sides or back with a splash. This habit enables them to be spotted from a considerable distance. When stressed, herds bunch tightly together, like the group in the bottom photo. (Photos from off Virginia by J. G. Mead [top] and off San Diego, Calif. by S. Leatherwood [bottom].)
Figure 134.—A saddleback dolphin stranded on Westerly Beach, R.I. The origin of the common name "crisscross dolphin" is evident in the color pattern of the side. Note also the distinctive black stripe from the center of the lower jaw to the origin of the flipper. (Photo courtesy of H. E. Winn.)
Sarawak dolphin, Bornean dolphin, Fraser's porpoise.
Fraser's dolphins reach an overall length of at least 8 feet (2.4 m). They are extremely short-beaked and have a pronounced dark stripe, similar to that found on the striped dolphin, extending from the rostrum to the area of the anus. They are robust in build and have rather small flippers and dorsal fin relative to body size. The dorsal fin is slender, falcate, and pointed on the tip. The body is gray on the back and white on the belly. The color of the side is dominated by the striping pattern. A cream-white band beginning high on the rostrum extends above and past the eye, continues towards the tail, and finally dissipates in the body color above the anus. Just below and parallel to this cream-white band is a black one extending from the area of the eye to the anus. A second cream-white band below and parallel to this dark strip separates the darker gray coloration of the side from the white coloration of the belly. The flippers are dark above and below.
The little that is known of the natural history and behavior of the species may be summarized as follows: Fraser's dolphins occur in groups of up to at least 500 animals and in the Pacific are occasionally seen with spotted dolphins (Stenella attenuata). From all accounts, they are not uncommon in certain areas of the tropical Pacific and off South Africa.
Fraser's dolphins appear to be deep divers. They are aggressive swimmers and, when they surface to breathe, often charge to the surface, creating a spray from their heads. They have also been reported leaping clear of the water.
Fraser's dolphin is intermediate in form betweenLagenorhynchusandDelphinus delphis(thus the composite nameLagenodelphis). Because the species is apparently limited to tropical waters, however, and because of the prominent stripe on the side of the body, Fraser's dolphins are more likely to be confused with the striped dolphins (p.113). The two species can be distinguished at sea by several characteristics:
Although Fraser's dolphins have yet to be described for the western North Atlantic Ocean, they are included here as "possibles" because of the recent discovery that their range is far more extensive than previously known. Records to date have been limited to offshore tropical waters.
The species was first described in 1956 from the remains of a beach-washed specimen from Sarawak in the South China Sea. Since that time specimens have been collected from the eastern tropical Pacific, and others have stranded in such widely divergent localities as Australia, South Africa, and Japan. Recent summaries have added sighting records from the Central Pacific, near the Phoenix Island, from northwest of the Galapagos Islands, and from South African waters.
Stranded Fraser's dolphins should be readily identifiable by 1) distinctive coloration of the body; 2) short, indistinctive beak; and 3) robust form. The only other species of small dolphins with beaks of similar length and general appearance are the Atlantic white-sided and white-beaked dolphins (p. 123 and 126); these dolphins, both with far more northerly ranges, have 30-40 and 22-28 teeth in each side of each jaw, respectively, while Fraser's dolphins have from 40 to 44 teeth in the upper jaw and from 39 to 44 in the lower jaw.
Figure 135.—Fraser's dolphins, like these photographed off the Phoenix Islands in the Pacific (top) and this one off the Philippines (bottom), are definitely identifiable in their tropical range by the short snout, the dark flank stripe and the small dorsal fin and flippers. They may reach 8 feet (2.4 m), or more, in length and occur in herds of at least 500 animals, sometimes with spinner dolphins or Atlantic spotted dolphins. (Photos by K. C. Balcomb [top] and T. Hammond [bottom].)
Figure 136.—Fraser's dolphins from the eastern tropical Pacific: adult (top and inset) and calf (bottom). Note the distinctive black lateral strip and the extremely small flippers and dorsal fin. (Photos by R. Garvie [top and inset] and S. Leatherwood [bottom].)
Atlantic white-sided porpoise, jumper (Newfoundland).
Atlantic white-sided dolphins reach about 9 feet (2.7 m) in maximum length and are robust in form with a small but distinct beak (less than 2 inches [5.1 cm] long).
The dorsal fin is tall, distinctly back curved, and pointed on the tip. The tail stock is extremely thick and does not narrow laterally until very near the tail flukes.
The back is distinctly black, the belly white. The sides have zones of gray, tan, and white.
The single most distinctive feature of Atlantic white-sided dolphins is an elongated oval zone of white and yellowish white along the sides from just below the dorsal fin to the area above the anus. These patches of lighter coloration, clearly demarcated from each other and from the surrounding coloration, are frequently visible simultaneously with the dorsal fin as the animals roll at the surface to breathe. Even alone this feature permits positive identification of the species. The dorsal fin is often part gray, part black. The beak is all black.
Atlantic white-sided dolphins are known to congregate in herds of perhaps a thousand animals, though smaller herds are far more common. The species is often wary of ships and does not ordinarily ride the bow wave. Like a number of other species, white-sided dolphins have been reported in association with Atlantic pilot whales.
At sea, Atlantic white-sided dolphins are most likely to be confused with the white-beaked dolphins, with which they overlap in distribution. Though they are very similar in general appearance, the two can be distinguished in the following ways:
Atlantic white-sided dolphins are distributed, primarily offshore, in the cool waters between the Gulf Stream and the Labrador Current. They have been observed from Hudson Canyon, off New York City, north to southern Greenland and perhaps Davis Straits. Their normal range shares a southern boundary with the white-beaked dolphin but does not extend as far to the north.
In addition to the features described above for living animals at sea, stranded Atlantic white-sided dolphins can be distinguished from white-beaked dolphins by the following:
Figure 137.—Atlantic white-sided dolphins at sea between Cape Cod, Mass. and Nova Scotia. This species can be positively identified by the elongated zone of white and the adjacent region of tan or yellowish tan below and behind the dorsal fin, visible even in the fast-swimming animal in the bottom picture. The top photo illustrates the origin of the Newfoundland common name "jumper." (Photos by K. C. Balcomb [top] and H. E. Winn [bottom].)
Figure 138.—An Atlantic white-sided dolphin off the eastern Canadian coast. These animals do not usually ride the bow wave, but when they can be examined at close range, they can be readily distinguished from their more northerly cousins, the white-beaked dolphins, by their highly distinctive color pattern. (Photo by P. B. Beamish.)
Figure 139.—The highly distinctive pattern of the Atlantic white-sided dolphins is clearly visible in this animal stranded in Scotland. Even if the color pattern has faded, however, this species should be easy to identify. The 30-40 teeth in each of the upper and lower jaws permit distinction from the white-beaked dolphins, which have only about 22-28 per side in each jaw. (Photos by B. Tullock, courtesy of A. S. Clarke.)
White-beaked porpoise, squidhound (Newfoundland).
White-beaked dolphins reach a maximum overall length of about 10 feet (3.1 m). The body is robust in form with a tall, uniformly dark-gray dorsal fin, and a short but distinct beak which, as the common name implies, is often light gray to white above and below, at least in European waters. The beak of animals in the western Atlantic populations is less frequently white. The back and sides are basically dark gray to black, and the belly is white to light gray.
Swimming white-beaked dolphins can be most readily identified by the two areas of pale coloration on the sides, one in front of and another below and behind the dorsal fin. These areas are clearly visible from a ship or aircraft as the animals roll at the surface.
White-beaked dolphins may sometimes occur in herds of up to 1,500 individuals. Like their cousins, the Atlantic white-sided dolphins, they do not commonly ride the bow waves of vessels.
White-beaked dolphins feed on squid, octopus, cod, herring, capelin, and sometimes on benthic crustaceans.
In their northerly range white-beaked dolphins are likely to be confused with only the Atlantic white-sided dolphins. The most distinctive features of white-beaked dolphins are 1) the two areas of paleness described above, 2) the prominent, dark gray dorsal fin, and sometimes 3) the white beak. Other features by which the two species may be distinguished in the brief encounters typical at sea are tabularized on p.127.
White-beaked dolphins are the more northerly of the two species ofLagenorhynchusin the western North Atlantic. They are found from Cape Cod, Mass., north to western and southern Greenland and Davis Straits, though they are apparently far more numerous to the north of this range. They appear in Davis Straits in spring and summer and leave that area in autumn, sometimes as late as November, to move southward. They winter as far south as Cape Cod, where they are the common dolphin species in April, May, and June (sometimes to July). Their migrations are poorly known.
Stranded white-beaked dolphins can be most readily distinguished from white-sided dolphins by the substantialdifferences in coloration and the differences in numbers of teeth.
Additional characteristics by which the two species may be distinguished are summarized on p.123.
Figure 140.—Two views of white-beaked dolphins off Newfoundland. This species is characterized by a prominent uniform dark gray dorsal fin and two areas of paleness on the sides, one in front of and one below and behind the dorsal fin. White-beaked dolphins are distributed from Newfoundland north, extending to more northerly waters than Atlantic white-sided dolphins. (Photos by H. E. Winn [bottom] and W. A. Watkins [top].)
Figure 141.—White-beaked dolphins reach nearly 10 feet (3.1 m) in length. Stranded animals, such as this specimen from Scotland, should be distinguishable from Atlantic white-sided dolphins by their differences in coloration. This species sometimes has a white beak and always lacks the elongated white patch and tan or yellow streaking found on the side of Atlantic white-sided dolphins. (Photos by A. S. Clarke.)
Bottlenosed porpoise, gray porpoise, common porpoise.[12]
[12]See also p.150for use of this common name for another species, the harbor porpoise.
[12]See also p.150for use of this common name for another species, the harbor porpoise.
Atlantic bottlenosed dolphins reach a maximum overall length of about 12 feet (3.7 m) and weigh in excess of 1,430 pounds (650 kg). They have relatively stubby snouts and dorsal fins, which are broad at the base, tall, and falcate. Coloration varies slightly, but individuals are usually dark gray on the back, lighter gray on the side, grading to white or pink on the belly. Old females may have spots on the belly. The dark coloration of the back often appears as a highly distinct cape, particularly on the head.
Atlantic bottlenosed dolphins often occur in groups of up to several hundred individuals which usually consist of aggregations of small groups of no more than a dozen animals each. They frequently associate with the Atlantic pilot whales and are frequently found accompanying the right and humpback whales travelling along the Atlantic coast of Florida.
Atlantic bottlenosed dolphins have catholic tastes, feeding on shrimp, eels, catfish, menhadden mullet, and miscellaneous trash fish, to mention only a few. They are frequently found near shrimp boats, feeding on fish stirred up by the trawls or on discarded trash fish.
They sometimes move in to ride the bow wave of a vessel, turning on their sides, sometimes spinning completely around on their longitudinal axis when doing so. Individuals may also turn their heads downward or to the side. They are often found close to shore, in bays and lagoons, and sometimes venture up the larger rivers. Some individuals, especially the larger animals, are found as far offshore as the edge of the continental shelf. Atlantic bottlenosed dolphins sometimes ride the surf. Individuals may jump clear of the water as high as 15-20 feet (4.6-6.1 m), a behavior on which aquarium shows have capitalized.
Members of this species are the dolphins most commonly maintained in captivity at zoos, aquariums, marine parks, and research institutions. For that reason, they are perhaps more familiar to the general public than any other species of porpoise, dolphin, or whale.
From at least Cape Hatteras southward, the range of the Atlantic bottlenosed dolphins distributed in inshore areas may overlap with that of Atlantic spotted dolphins, particularly during the spring and summer, when the Atlantic spotted dolphins move inshore. There the two species may be confused. The Atlantic bottlenosed dolphins and the Atlantic spotted dolphins can be distinguished, however, by the following characteristics:
Some Atlantic bottlenosed dolphins are distributed well offshore as far as the edge of the continental shelf. Those individuals may be confused with either rough-toothed dolphins (p.135) or with grampus (p.96). They may be distinguished from rough-toothed dolphins by the following:
Distinguishing differences between the Atlantic bottlenosed dolphins in offshore areas and grampus are tabularized on p.96.
In northeastern South America the range of the Atlantic bottlenosed dolphin apparently overlaps with that of the Guiana dolphin, which, except for size, it closely resembles (see p.132).
The Atlantic bottlenosed dolphins are widely distributed in the temperate and tropical waters of the western Northbest known from New England southward to Florida, westward in the Gulf of Mexico, and thence throughout the West Indies and Caribbean to Venezuela.
In the northern portion of that range, Atlantic bottlenosed dolphins are distributed offshore. In the southern portions of their range from at least North Carolina southward, the majority are found nearshore and often enter bays and lagoons, and sometimes venture up the larger rivers. Daily migrations in these areas may follow tidal flow.
In these same southerly areas some Atlantic bottlenosed dolphins are distributed as far offshore as the edge of the continental shelf.
Within their range, stranded Atlantic bottlenosed dolphins should be readily identifiable by 1) the robust body, 2) relatively short beak, and 3) the 20-26 teeth in each upper jaw and 18-24 in each lower jaw.