Chapter IV: Part 4

Dark purplish gray on back; Dark gray on back; lighter
lighter gray on sides and gray on sides; white or pink
belly; body becomes on belly (old animals may
increasingly spotted with age. have a few spots on belly,
but most are not spotted).

HEAD AND BEAK

Head more slender; beak Head robust; beak short;
longer; lips and top of snout beak usually uniformly gray
often white. (older animals' beak may be
white at tip).

NORMAL DISTRIBUTION

Usually found more than 5 Usually more coastal, often
miles offshore; most common ascending rivers and entering
inside 100-fathom curve. lagoonal and estuarine
areas.

Young Atlantic spotted dolphins are so similar in appearance to the Atlantic bottlenosed dolphins that the frequent reports of mixed schools of the two species are probably occasioned by groups of spotted dolphins which include some young, still unspotted animals.

Atlantic spotted dolphins might also be confused with bridled dolphins. The two can be most readily distinguished by the following characteristics:

ATLANTIC SPOTTED DOLPHIN BRIDLED DOLPHIN

BODY SHAPE

Usually robust, often like More slender, more like
that of the Atlantic that of the Atlantic striped
bottlenosed dolphin. dolphin.

BODY COLOR

Spotted; purplish gray on Spotted; side of head light
back; lighter gray on sides gray; body has stripe from
and belly becoming flipper to corner of mouth,
increasingly spotted with age. though the stripe tends to
As animals becomes more fade as spotting increases.
spotted, cape become less Cape on top of head more
distinct. Body has spinal distinct that on Atlantic
blaze and light line from spotted dolphin. Body has no
flipper to eye. spinal blaze.

At sea the Atlantic spotted dolphins may also be confused with rough-toothed dolphins (p. 135).

Distribution

Atlantic spotted dolphins are a common species in the continental waters of the tropical and warm temperate western North Atlantic. Although they are far more abundant south of Cape Hatteras, they have been reported from the latitude of Cape May, N.J. (some fishermen claim to have seen them even further north) south through the Gulf of Mexico and the Caribbean to Venezuela. Atlantic spotted dolphins may be replaced around the West Indies by the bridled dolphin.

Within this range, the Atlantic spotted dolphins appear to be generally restricted to the waters outside the 100-fathom curve, most commonly more than 5 miles offshore. However, populations in the Gulf of Mexico move inshore in the late spring, and may approach close to shore during spring and summer.

Stranded Specimens

Stranded Atlantic spotted dolphins may be difficult to distinguish from bridled dolphins. If the color pattern is still clearly visible, the differences in coloration described above, particularly those of the head, and the presence or absence of a spinal blaze may be used. But since external appearance other than coloration are often very similar, specimens should be photographed from as many aspects as possible and the entire specimen or the roughed-out complete skeleton transported to a museum for preparation and examination. Tooth counts recorded for the two species to date are also very similar.

BRIDLED DOLPHIN (T)

_Stenella frontalis_ (G. Cuvier 1829)

Other Common Names

Bridled spotted dolphin, Cuvier's dolphin, gamin (St. Vincent), bridled porpoise.

Description

Bridled dolphins, the second species of spotted dolphins in the western North Atlantic, reach an adult length of at least 7 feet (2.1 m). Like the other, the Atlantic spotted dolphin (p. 104), bridled dolphins are characterized by light grayish-white spots on the dark dorsal portions of the body and dark spots on the light ventral surface. Other details of the coloration differ somewhat. Bridled dolphins are dark gray on the back, fading to lighter gray on the sides and belly. They lack the spinal blaze characteristic of Atlantic spotted dolphins. Except on the head, the border between the back and side colors is indistinct. On the head, the cape (the dark color of the top of the head) is distinct. In the light gray of the side of the head are the markings from which the species derives its common name, "bridled dolphin." These are a black circle around the eye with an extension to the junction (apex) of the rostrum and the melon (present in nearly all dolphins) and a broad black stripe from the origin of the flipper to the corner of the mouth. This mouth-to-flipper stripe tends to fade as spotting increases. Both the upper and lower lips are white or pinkish.

Natural History Notes

Virtually nothing is known of the natural history of bridled dolphins except that they have been observed in small herds of from 5 to 30 individuals and sometimes ride the bow wave of a vessel.

May Be Confused With

At sea, bridled dolphins may be confused with Atlantic spotted dolphins or spinner dolphins. Differences by which they may be distinguished from the first are tabularized on p. 105. Differences between spinner and bridled dolphins permitting identification at sea are as follows:

BRIDLED DOLPHIN SPINNER DOLPHIN

COLORATION

Distinct cape on top of head; Dark gray on back; tan or
side of head light gray; yellowish tan on sides; white
distinct stripes from flippers on belly,
to corner of mouth and from
dark circles around eye to
apex of melon.

BEAK

Shorter and more slender; all Extremely long and slender;
black; lips white. dark gray to black on top,
white below; lips black.

DORSAL FIN

Uniformly dark gray. Often lighter gray in middle,
dark around border.

Distribution

Bridled dolphins occur in tropical and subtropical waters primarily near coastal areas and islands, but are best known from the West Indies. They have been reported from the Antilles, from Texas, and from Florida north to North Carolina. It has been speculated that this species replaces the Atlantic spotted dolphin around the West Indies.

Bridled dolphins have not yet been described from the South American coast.

Stranded Specimens

Bridled dolphins have from 29 to 34 teeth in each upper jaw and from 33 to 36 in each lower jaw. They can be distinguished from spinner dolphins, which have 46-65 teeth in each jaw, by this character alone.

They may be distinguished from spotted dolphins only if the color pattern of the head is clearly visible. If it has faded, the specimen will probably require museum preparation and examination before it can be positively identified.

SPINNER DOLPHIN (T)

_Stenella longirostris_ Gray 1828

Other Common Names

Long-snouted dolphin, long-beaked porpoise, spinner porpoise, rollover (St. Vincent).

Description

Spinner dolphins reach a maximum length of about 7 feet (2.1 m). The body is slender. The beak varies from extremely long and slender (Fig. 123) to relatively short (Fig. 125); the beak is usually dark on top and clean white below, though there may be some white above. The tip of the snout and the lips are distinctly black, while those of both species of spotted dolphins are light. The back is dark gray to black, the sides are tan to yellowish brown, and the belly is white. Some of the larger animals appear almost all black with faint, light speckling. The dorsal fin is generally moderately falcate, but may be almost triangular in adult males. It is often a lighter gray near the middle, bordered by black or dark gray.

Natural History Notes

Spinner dolphins derive their common name from their habit of leaping clear of the water and spinning on their longitudinal axis. The reasons for this behavior are unknown. Individuals may rotate 2 times, or more, in one leap but spinning behavior is not observed as frequently in the western North Atlantic as it is in the eastern tropical Pacific.

Spinner dolphins occur in herds of up to several hundred individuals and are often seen jumping clear of the water, working the sea surface into a froth. They frequently come to the bow of a boat from considerable distances to ride in the bow wave and may ride for protracted periods.

May Be Confused With

Spinner dolphins may be confused with saddleback dolphins. Both species occur in large herds and often come to moving vessels to ride the bow wave. The two can be distinguished, however, by these differences:

SPINNER DOLPHIN SADDLEBACK DOLPHIN

COLORATION

Dark gray on back; tan or Dark gray to brownish gray
yellowish tan on sides; white on back; white on belly with
on belly; lacks crisscross crisscross or hourglass pattern
pattern on sides; distinct of tan to yellow on sides;
black stripe from flipper to distinct black stripe from
eye. flipper to middle of lower
jaw.

Spinner dolphins might also be confused with bridled dolphins, but may be distinguished by the differences summarized on p. 108.

Distribution

Spinner dolphins are distributed in oceanic and coastal tropical waters. Though one specimen was collected from South Carolina, they have been more frequently reported from both coasts of Florida, the Gulf of Mexico, the Caribbean, and the West Indies. They have also been reported from Venezuela. They are said to be the most abundant dolphin species from the southeastern Caribbean. Some Pacific spinner dolphins are distributed in oceanic zones. Atlantic spinners may be abundant in offshore tropical waters as well.

Stranded Specimens

Stranded spinner dolphins are most readily identified by the extremely long rostrum and the 46-65 teeth, far more than any other species of dolphin. Note that the striped dolphins may have from 43 to 50 teeth per side in each jaw. However, striped dolphins are decidedly larger (to about 9 feet [2.7 m]), have a shorter beak, and are distinctly marked with dark stripes from the eye to the flipper, from the eye to the anus, and from the area behind the dorsal fin forward, towards but not reaching the head.

Saddleback dolphins also have from 40 to 50 teeth on each side but are also easily distinguishable by the differences in coloration discussed above for living animals at sea.

STRIPED DOLPHIN (T)

_Stenella coeruleoalba_ (Meyen 1833)

Other Common Names

Euphrosyne dolphin (_Stenella styx_), Meyen's dolphin, blue-white dolphin, Gray's dolphin, striped porpoise, streaker porpoise.

Description

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.

Natural History Notes

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.

May Be Confused With

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 DOLPHIN SADDLEBACK DOLPHIN

LENGTH

To about 9 feet (2.7 m) or Seldom greater than 7.5 feet
more. (2.3 m).

COLORATION

Back from light gray to dark Back basically black or
gray to bluish gray; sides brownish; distinct white
gray; belly gray or white; chest or belly patch;
distinctive black lateral hourglass or crisscross
stripping from 1) eye to pattern on the sides;
flipper, 2) eye to anus, and 3) distinct black stripe from
dark color behind dorsal fin flipper to middle of lower
forward, towards but not jaw.
reaching head.

Distribution

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 Specimens

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).

SADDLEBACK DOLPHIN (T)

_Delphinus delphis_ Linnaeus 1758

Other Common Names

Saddleback porpoise, common dolphin, crisscross dolphin.

Description

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.

Natural History Notes

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.

May Be Confused With

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:

SADDLEBACK DOLPHIN STRIPED DOLPHIN

COLORATION

Back basically black or Back from light gray to dark
brownish; distinct white gray to bluish gray; sides
chest or belly patch; hourglass gray; belly gray or white;
or crisscross pattern on distinctive black lateral
sides, some tan to yellowish striping from 1) eye to
tan; distinct black stripe flipper, 2) eye to anus, and
from flipper to middle of 3) dark color behind dorsal
lower jaw. fin forward, towards but not
reaching head.

LENGTH

To 7.5 feet, rarely to 8.5 feet To 9 feet (2.7 m).
(2.3-2.6 m).

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 DOLPHIN SPINNER DOLPHIN

COLORATION

Dark gray to brownish gray Dark gray on back; tan or
on back; white on belly with yellowish tan on sides; white
crisscross or hourglass pattern on belly; lacks crisscross
of tan to yellowish tan pattern on sides; distinct
on side; distinct black stripe black stripe from flipper to
from flipper to middle of eye.
lower jaw.

Distribution

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.

Stranded Specimens

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 from both 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).

FRASER'S DOLPHIN (T)

_Lagenodelphis hosei_ Fraser 1956

Other Common Names

Sarawak dolphin, Bornean dolphin, Fraser's porpoise.

Description

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.

Natural History Notes

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.

May Be Confused With

Fraser's dolphin is intermediate in form between _Lagenorhynchus_ and _Delphinus delphis_ (thus the composite name _Lagenodelphis_). 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:

FRASER'S DOLPHIN STRIPED DOLPHIN

COLORATION

Single broad black stripe Color dominated by series of
from beak and eye back to stripes from: 1) eye to anus;
area of anus. 2) eye to flipper, and 3)
black behind dorsal fin
forward, towards but not
reaching the head.

BEAK

Extremely short and indistinct. Longer, much more distinctive.

BODY SHAPE

Robust, particularly in front Slenderer.
of dorsal fin.

FLIPPERS

Small, dark in color, and Longer, sometimes lighter
originating in light color of on upper surface; note stripe
sides. from front of flippers to eye.

DORSAL FIN

Small, slender, slightly Taller dorsal fin, broader at
falcate, and pointed on top. base.

Distribution

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 Specimens

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.

ATLANTIC WHITE-SIDED DOLPHIN (T)

_Lagenorhynchus acutus_ (Gray 1828)

Other Common Names

Atlantic white-sided porpoise, jumper (Newfoundland).

Description

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.

Natural History Notes

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.

May Be Confused With

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
DOLPHIN WHITE-BEAKED DOLPHIN

COLORATION

Elongated band of yellowish Two grayish areas--one in
white and white along side, front, the other below and
visible behind and below behind dorsal fin, visible as
dorsal fin as animal rolls. animal rolls.

BEAK

All black. Sometimes white in parts of
range though western Atlantic
animals are usually dark.

MAXIMUM SIZE

To 9 feet (2.7 m). To 10 feet (3.1 m).

DORSAL FIN

Often part black, part lighter Uniformly dark.
gray.

Distribution

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.

Stranded Specimens

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:

ATLANTIC WHITE-SIDED
DOLPHIN WHITE-BEAKED DOLPHIN

NUMBER OF TEETH

30-40 per side per jaw, 22-28 per side per jaw; have
sometimes more in upper. larger individual teeth--to 6
mm in diameter.

FLIPPERS

Lower portion of forward Lower portion of forward
margin more curved. margin less acutely curved.

VENTRAL COLOR

White coloration of belly White coloration of belly
extends high onto sides of extends to lower jaw but not
body. above flippers on sides.

CAUDAL CRESTS

Tail stock strongly compressed Tail stock less laterally
laterally; taller, narrows compressed, tapers more
rapidly just in front of flukes. gently towards tail flukes.

WHITE-BEAKED DOLPHIN (T)

_Lagenorhynchus albirostris_ Gray 1846

Other Common Names

White-beaked porpoise, squidhound (Newfoundland).

Description

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.

Natural History Notes

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.

May Be Confused With

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.

Distribution

White-beaked dolphins are the more northerly of the two species of _Lagenorhynchus_ in 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 Specimens

Stranded white-beaked dolphins can be most readily distinguished from white-sided dolphins by the substantial differences in coloration and the differences in numbers of teeth.

ATLANTIC WHITE-SIDED
WHITE-BEAKED DOLPHIN DOLPHIN

TEETH

22-28 per side per jaw. 30-40 per side per jaw,
sometimes more in upper
jaw.

COLORATION

Beak sometimes gray or Beak all black; side marked
white above and below; two with elongated areas of
pale areas visible on living white with streaking patterns
animals not visible on stranded of yellow and tan.
specimens.

Additional characteristics by which the two species may be distinguished are summarized on p. 123.

ATLANTIC BOTTLENOSED DOLPHIN (T)

_Tursiops truncatus_ (Montague 1821)

Other Common Names

Bottlenosed porpoise, gray porpoise, common porpoise.[12]

[Footnote 12: See also p. 150 for use of this common name for another species, the harbor porpoise.]

Description

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.

Natural History Notes

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.

May Be Confused With

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:

ATLANTIC ATLANTIC
BOTTLENOSED DOLPHIN SPOTTED DOLPHIN

MAXIMUM SIZE

8 feet to as much as 12 feet 7.5-8 feet (2.3-2.4 m).
(2.4 to 3.7 m).

COLORATION

Not spotted (old females may Dark purplish gray on back;
have spots on belly); dark lighter gray on sides and
gray on back; light gray on belly; body becomes increasingly
sides; white or pink on belly. spotted with age.

HEAD AND BEAK

Head robust; beak relatively Head more slender; beak
short. longer.

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:

ATLANTIC BOTTLENOSED
DOLPHIN ROUGH-TOOTHED DOLPHIN

BODY COLOR

Dark gray on back; light Dark gray, almost purplish
gray on side; white or pink on with yellow spots; lighter on
belly. belly.

SNOUT

Relatively short and stubby, Long and slender; not
and clearly demarcated from clearly demarcated from
forehead; usually all gray; forehead; lower jaw and lips
some older individuals have speckled white.
white-tipped snouts and/or
white lips.

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).

Distribution

The Atlantic bottlenosed dolphins are widely distributed in the temperate and tropical waters of the western North Atlantic. They are known from at least Nova Scotia but are best 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.

Stranded Specimens

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.

GUIANA DOLPHIN (T)

_Sotalia guianensis_ (P.-J. van Beneden 1864)

Other Common Names

None known.

Description

Guiana dolphins are the second smallest cetacean species in the western North Atlantic, reaching a maximum length of only about 5.6 feet (1.7 m).

Their body shape is very similar to that of the Atlantic bottlenosed dolphin, though the beak is less clearly demarcated from the forehead.

The rather prominent dorsal fin is nearly triangular, curving only slightly backwards near the tip.

Guiana dolphins are steel blue to dark brown on the back and white on the belly. There is sometimes a brownish band extending from the dark color of the back in front of the dorsal fin back towards but not reaching the anus.

Natural History Notes

Guiana dolphins are usually found in groups of fewer than 10 individuals.

May Be Confused With

Because of their limited range and specialized habitats, Guiana dolphins are unlikely to be confused with any other cetacean species except perhaps Atlantic bottlenosed dolphins (p. 128). These two species can be distinguished by the following characteristics:

GUIANA DOLPHINS ATLANTIC BOTTLENOSED
DOLPHINS

SIZE

To only 5.6 feet (1.7 m). 8 to as much as 12 feet
(2.4 to 3.7 m).

DORSAL FIN

More nearly triangular; curved Broad-based, tall, and
only slightly backwards falcate.
near tip.

DISTRIBUTION

Found in rivers and estuaries, Sometimes found nearshore
extend into only very and in bays, river mouths,
shallow nearshore waters on and estuaries, but extend
limited area of South American farther offshore.
coast.

Distribution

Guiana dolphins are found in Lake Maracaibo, in the rivers of Guyana, and in the nearshore coastal waters of the northeastern portion of the Guianas.

Stranded Specimens

In their very limited range, stranded Guiana dolphins can be readily identified by their extremely small size (to 5.6 feet [1.7 m]) and nearly triangular dorsal fin. Furthermore, in addition to the characteristics listed above distinguishing living Guiana dolphins from Atlantic bottlenosed dolphins, the species can be distinguished by differences in the numbers of teeth:

ATLANTIC BOTTLENOSED GUIANA DOLPHINS
DOLPHINS

TEETH

20-26 in each upper jaw; 26-35 in each jaw; often
18-26 in each lower jaw. ragged in arrangement.

ROUGH-TOOTHED DOLPHIN (T)

_Steno bredanensis_ (G. Cuvier in Lesson 1828)

Other Common Names

Rough-toothed porpoise, goggle-eyed porpoise.

Description

Rough-toothed dolphins reach a length of at least 8 feet (2.4 m). The coloration of the rough-toothed dolphins is quite variable. Individuals are often dark gray to dark purplish gray on the back with pinkish-white blotches on the sides and belly. The flippers and flukes are dark and the belly is white. Individuals are frequently scarred with numerous white streaks.

The most distinctive characteristic of the rough-toothed dolphin is its beak, which is quite long and slender, may be white or pinkish white along both sides, including one or both lips and the tip of the snout, and is not separated from the forehead by the transverse groove present in other long-snouted dolphins. Because the forehead and the sides of the head slope smoothly into the rostrum, when this animal is seen from above or from the side, its entire head appears very long and nearly conical.

Natural History Notes

Rough-toothed dolphins occur in small groups of 50 animals or fewer and are usually found off the edge of the continental slope. They may ride the bow waves.

May Be Confused With

In their offshore habitat, rough-toothed dolphins are most likely to be confused with Atlantic spotted dolphins (p. 104) and with Atlantic bottlenosed dolphins (p. 128). They may be distinguished from Atlantic spotted dolphins by the following:

ROUGH-TOOTHED DOLPHIN ATLANTIC SPOTTED DOLPHIN

SNOUTS

Long and slender; not clearly Moderate in length and
demarcated from forehead. clearly demarcated from
forehead.

They may be distinguished from Atlantic bottlenosed dolphins by the characteristics tabularized on p. 128.

Even at a distance the blotched coloration of the side and the white coloration of the rostrum of rough-toothed dolphins may be visible. If closer examination is possible, the distinctive shape and coloration of the beak make positive identification easy.

Distribution

Though records of rough-toothed dolphins from the western North Atlantic are scant, the species is assumed to be widely distributed in deep tropical to warm temperate waters. It has been reported from Virginia, Georgia, Florida, the Gulf of Mexico, the West Indies, and off the northeastern coast of South America.

Stranded Specimens

In addition to the characteristics listed above for distinguishing living animals, stranded rough-toothed dolphins can be readily identified by the fact that the 20-27 fairly large teeth per jaw per side have a series of fine vertical wrinkles on the crown, a characteristic from which the species derives its common name. (These wrinkles are often difficult to detect.)

PYGMY KILLER WHALE (T)

_Feresa attenuata_ Gray 1874

Other Common Names

Slender blackfish, slender pilot whale.

Description

Pygmy killer whales reach a length of about 8-9 feet (2.4-2.7 m). They are usually relatively slender-bodied with a rounded head, an underslung jaw, and no beak.

The falcate dorsal fin, located about the center of the back, is usually between 8 and 12 inches (20.3 and 30.1 cm) tall (though it may reach 15 inches [38 cm] in some individuals), is sometimes very distinctive, and resembles that of the Atlantic bottlenosed dolphin. The flippers are slightly rounded on the tips.

The color has been described as dark gray or black on the back, often lighter on the sides, extending higher in front of the dorsal fin and with a small zone of white on the underside, often a lighter gray area on the sides, and distinctive white regions around the lips. The chin may be completely white. This white zone on the chin, described as a "goatee," is often clearly visible in swimming animals.

May Be Confused With

The pygmy killer whale resembles the false killer whale but is much smaller and can be distinguished at close range by the zones of white coloration. False killer whales are almost all black and reach a length of up to at least 18 feet (5.5 m). Pygmy killer whales are dark gray on the back, often lighter on the sides, and show a region of white on the belly which may extend so high up onto the sides that it is visible on a swimming animal. Further, they reach only 8-9 feet (2.4-2.7 m).

Pygmy killer whales may also be confused with the similarly sized and colored many-toothed blackfish. So little is known of the two species' appearance and behavior at sea that it is doubtful that they can be successfully distinguished, though many-toothed blackfish apparently lack the white region often seen on the sides of pygmy killer whales. Further, pygmy killer whales have rounded flippers and smoothly tapered heads, while those of the many-toothed blackfish are pointed on the tip and more sharply pointed (often described as a parrot beak).

Distribution

Pygmy killer whales are probably distributed in the tropical and subtropical waters of the western North Atlantic. They have been reported from Texas, the Atlantic coast of Florida, and St. Vincent Island, Lesser Antilles. Records of the species from the other oceans of the world suggest that its distribution is limited to tropical and subtropical waters.

Stranded Specimens

Stranded pygmy killer whales can be clearly distinguished from both the false killer whale and the many-toothed blackfish. In addition to the differences discussed above, the following are key differences between the pygmy and false killer whales:

PYGMY KILLER WHALE FALSE KILLER WHALE

TEETH

10-13 in each side of upper 8-11 per jaw per side,
and lower jaws; lower teeth prominent.
smaller.

VENTRAL COLORATION

White from anus to under tail Dark from anus to tail stock;
stock, white may extend up lighter pale gray area forward
sides. between flippers.

FLIPPERS

Smoothly rounded. Characteristic hump on forward
margin.

Pygmy killer whales can be distinguished from many-toothed blackfish on the basis of the second species' larger number of teeth. (Many-toothed blackfish have from 22 to 25 teeth in the upper jaw and from 21 to 24 in the lower jaw.)

MANY-TOOTHED BLACKFISH (T)

_Peponocephala electra_ (Gray 1846)

Other Common Names

Hawaiian blackfish, melon-headed whale.

Description

Many-toothed blackfish reach lengths of at least 9 feet (2.7 m) and are similar in body shape to the larger false killer whale and the similar-sized pygmy killer whale. The body is elongated and slim with a rather slim tail stock. In general, the head is shaped like that of the false killer whale but has a sharper appearance to the snout, sometimes described as a parrot-beak. The forehead is rounded, slightly overhanging the lower jaw, and has no beak. The dorsal fin is up to 10 inches (25.4 cm). It is probably very distinctive as the animals surface to breathe. Many-toothed blackfish are black on the back and slightly lighter on the belly. The areas around the anus and genitals and the lips are unpigmented. Many-toothed blackfish are presumably rare.

May Be Confused With

Many-toothed blackfish may be confused with either the false killer whale or the pygmy killer whale. They are considerably smaller than the false killer whale, have a slightly more pointed snout, and lack the prominent humplike forward margin on the flippers which is characteristic of the false killer whale.

They are approximately the same size as pygmy killer whales, but the white area around the genitals which extends up onto the side in pygmy killer whales may be lacking in many-toothed blackfish. This species has pointed flippers, while those of pygmy killer whales are rounded on the tips. Many-toothed blackfish also have a slightly more pointed snout. Otherwise, the two species are virtually indistinguishable in encounters at sea.

Distribution

Although many-toothed blackfish have not yet been reported in the western North Atlantic, they are included in this guide because of a record from the eastern tropical North Atlantic and the known tropical distribution in other areas.

Stranded Specimens

Stranded many-toothed blackfish can be distinguished from false killer and pygmy killer whales by the number of teeth alone. Many-toothed blackfish have more than 15 per side per jaw (usually 21-25); both other species have less than 15.

PYGMY SPERM WHALE (T)

_Kogia breviceps_ (Blainville 1838)

Other Common Names

None known.

Description

Pygmy sperm whales reach a length of at least 11 feet (3.4 m). They are characterized by 1) an extremely robust body that rapidly tapers near the tail, 2) a squarish head, and 3) a narrow, underslung lower jaw which is located well behind the tip of the snout. Along the side of the head, in approximately the same position where gill slits would be located on a fish of comparable size, there is a crescent-shaped bracket mark, often called a false gill.

The flippers, which are smoothly curved on the forward margin and may reach a length of 18 inches (45.7 cm) or more on an adult specimen, are located well forward on the body, just below and behind the bracket mark.

The dorsal fin is very small, falcate, and located in the latter half of the back.

Though coloration can be described only from stranded specimens and a few encounters with living animals, pygmy sperm whales appear to be dark steel gray on the back, shading to a lighter gray on the sides, and gradually fading to a dull white on the belly. The outer surface of the flippers and the upper surface of the tail flukes are also steel gray.

Natural History Notes

From the few accounts, the following may be summarized about the behavior of pygmy sperm whales at sea: They reportedly usually rise slowly to the surface to breathe, produce a blow that is inconspicuous, and do not normally roll aggressively at the surface like most other species of small whales. They reportedly fold their flippers flat against their bodies when swimming. They have been reported to lie motionless in the water with the back of the head on the surface and the tail hanging loosely down in the water. (A similar behavior in sperm whales has made them a minor hazard to shipping, since it has resulted in some collisions with ships.) When they are startled in this posture, they may defecate, issuing a cloud of reddish brown to rust-colored fece. Beached pygmy sperm whales have also been observed to defecate a fine chocolate feces.

Pygmy sperm whales apparently feed primarily on squid, but do take fish as well.

May Be Confused With

In general, when they can be examined at close range, pygmy sperm whales are so distinctive that they are unlikely to be confused with any other species except perhaps the dwarf sperm whales. At a distance, they might be confused with small individuals of any of the beaked-whale species (p. 78) that also have a relatively small, falcate dorsal fin located in the latter third of the back. Closer examination should permit easy separation, however, since the pygmy sperm whale has a blunted head, while the beaked whales, as the name implies, have elongated "dolphinlike" beaks and are considerably larger. At sea, pygmy sperm whales are most likely to be confused with their cousins the dwarf sperm whales (p. 148 and Fig. 160). The two species can be distinguished as follows:

PYGMY SPERM WHALE DWARF SPERM WHALE

MAXIMUM SIZE

To 11 feet (3.4 m). To 9 feet (2.7 m).

DORSAL FIN

Small to 8 inches (20.3 cm), Taller, more like that of
falcate; located in latter third bottlenosed dolphins; located
of back. near the midpoint of the
back.

COLORATION

Both species are dark steel gray on the back, grading to
lighter on the belly.

Distribution

Because they have been rarely observed at sea, normal ranges for this species are not known. Based on stranding records, however, the following can be stated. In the western North Atlantic, pygmy sperm whales have been found as far north as Sable Island, Halifax, Nova Scotia, as far south as Cuba, and as far west as Texas in the Gulf of Mexico. They are frequently found stranded along the Atlantic coast of Florida and throughout the eastern and northern Gulf of Mexico.

Stranded Specimens

Because of the distinctive characters of the genus, stranded pygmy and dwarf sperm whales are unlikely to be confused with any other species of cetacean, though the rather narrow underslung jaw and the blunted head may result in their casual dismissal by some beach walkers as stranded sharks. The two species of Kogia may be distinguished by the following:

PYGMY SPERM WHALE DWARF SPERM WHALE

TEETH

12-16 (rarely 10-11) in lower 8-11 (rarely 13) small and
jaw are larger; no teeth in extremely sharp teeth in
upper. lower jaw; sometimes have
up to 3 teeth in each upper
jaw.

THROAT

No creases or grooves on Several short irregular creases
throat. or grooves on throat.

DWARF SPERM WHALE (T)

_Kogia simus_ (Owen 1866)

Other Common Names

Rat porpoise (West Indies).

Description

Dwarf sperm whales reach an overall length of approximately 9 feet (2.7 m). Like the other species of _Kogia_, the pygmy sperm whale (p. 144), the dwarf sperm whales are characterized by 1) a squarish head, 2) an extremely robust body which tapers rapidly near the tail stock, 3) a narrow, underslung lower jaw, and 4) a bracket mark or false gill on the side of the head.

The dorsal fin of this species is tall and falcate, closely resembling that of the Atlantic bottlenosed dolphin, and is located near the midpoint of the back. There are several short, irregular creases or grooves on the throat similar to those found on the sperm whale (see Figs. 60, 165).

Dwarf sperm whales are dark steel gray on the back, grading to lighter gray on the sides, and fading to dull white on the belly.

May Be Confused With

Because of their tall, falcate dorsal fin, dwarf sperm whales may be confused at a distance with any of the small dolphin species. Their all-black or dark steel-gray coloration and the blunted head increase the likelihood that they can be confused with pygmy killer whales or many-toothed blackfish. They will have to be examined at close range before they can be distinguished.

Dwarf sperm whales may also be confused with pygmy sperm whales (p. 144 and Fig. 160). The two species can be differentiated by the characteristics tabularized on p. 144.

Distribution

Since it has only recently been recognized as a species distinct from the pygmy sperm whale and even more recently given a common name, records of dwarf sperm whales may have been confused with those of its close relatives. The dwarf sperm whale has been reported from at least Georgia south to St. Vincent, Lesser Antilles, and throughout the eastern and northern Gulf of Mexico. It is highly likely that this species, like the pygmy sperm whale, extends further to the north.

Stranded Specimens

Because of the distinctive characteristics of the genus, neither species of stranded _Kogia_ is likely to be confused with any other species. They can be distinguished from one another by the characteristics tabularized on p. 144.

HARBOR PORPOISE (T)

_Phocoena phocoena_ (Linnaeus 1758)

Other Common Names

Common porpoise, herring hog, puffing pig (Newfoundland and New England), Pourcils (Quebec), harbour porpoise.

Description

The harbor porpoise is the smallest cetacean species in the western North Atlantic Ocean, reaching a maximum overall length of about 5 feet (1.5 m). Its most distinctive identifying features in encounters at sea are 1) the small, chunky body; 2) the coloration, dark brown or gray on the back, fading to lighter grayish brown on the sides, often with speckling in the transition zone, and white on the belly extending farther up on the sides in front of the dorsal fin; 3) the small rounded head, lacking a distinctive beak; 4) the small, triangular dorsal fin; and 5) the shallow, inshore northerly distribution.

Natural History Notes

As the name implies, the harbor porpoise inhabits bays, harbors, river mouths, and all the relatively shallow inshore water between. Though it may travel in schools of nearly a hundred individuals, it is more often seen in pairs or in small groups of from 5 to 10 individuals. It often swims quietly at the surface. It will not ride the bow wave and is very difficult to approach closely by boat.

May Be Confused With

The harbor porpoise is not known to associate with dolphins but is sometimes seen in close proximity to fin whales and humpback whales off the Canadian coast in spring and summer. Because of its northern inshore habitat, the harbor porpoise is not likely to be confused with any other cetacean.

Distribution

Harbor porpoises are restricted to the colder waters of the western North Atlantic Ocean. They have been reported from North Carolina north to the Davis Straits and the waters of southwestern Greenland. Within this range they are probably most common in the Bay of Fundy and off southwest Greenland.

Stranded Specimens

In addition to the characteristics described above for living animals, stranded harbor porpoises can be readily identified by the small spade-shaped teeth, 22-28 per jaw.

), the small triangular dorsal fin, the dark brownish color of the back, and the lighter color of the sides and belly intruding higher up in front of the dorsal fin. Harbor porpoises frequent inshore areas, shallow bays, estuaries and harbors, and reportedly do not approach moving vessels nor ride bow waves. (_Photos by J. D. Hall._)]

ACKNOWLEDGMENTS

Obviously this guide could not have been produced without the cooperation of many people. Of over 450 individuals and scientific organizations contacted in 14 countries, 255 responded to our letters and well over 100 provided photographs for review and selection. We were particularly pleased that for the majority of the species found in the western North Atlantic our most difficult problem was narrowing the choices and ultimately selecting illustrations from the many good materials made available to us. Although there are far too many contributors to mention all by name, their prompt and enthusiastic responses to requests for help are gratefully acknowledged, whether or not their materials were used.

Although photo credits follow each figure, we would particularly like to cite the generosity of Marineland of Florida, Hideo Omura of the Japanese Whales Research Institute, J.G. Mead of the U.S. National Museum, K.C. Balcomb of Moclips Cetological Society, Seiji Ohsumi of the Far Seas Fisheries Research Laboratory, Jack Lentfer of the Alaskan Department of Fish and Game, the U.S. Naval Undersea Center (NUC), The University of Rhode Island, and William F. Perrin of the National Marine Fisheries Service (NMFS). Photographs by Taruski, McCann, Hain, Wheeler, and Rigley are in Winn's files. All others are in the files of Leatherwood and Caldwell. The illustrations for Figures B1 and D1 were prepared by George Galich of NUC. All other illustrations were prepared by Lois Winn.