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.
[Illustration: 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._)]
[Illustration: 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)._)]
[Illustration: 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 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.
[Illustration: 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)._)]
[Illustration: 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._)]
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.
[Illustration: Figure 142.--Atlantic bottlenosed dolphins leaping on the
bow of a research vessel between Cape Cod, Mass. and Nova Scotia. Note
the robust body, the falcate dorsal fin, and the gradation of color in
three zones--dark gray on the back, to lighter gray on the sides, to
white or pink on the belly. (_Photo by A. Taruski._)]
[Illustration: Figure 143.--A side view of the Atlantic bottlenosed
dolphins off St. Augustine, Fla. Note the dark grayish coloration of the
back, the lighter coloration of the side, and the tall, sharply angled
dorsal fin, pointed on the tip. Though dorsal fin shapes are highly
variable, dorsal fins of the Atlantic bottlenosed dolphin are usually
more falcate and less pointed on the tip than on these animals. (_Photo
courtesy of Marineland of Florida._)]
[Illustration: Figure 144.--Atlantic bottlenosed dolphins frequently
ride the bow wave, often turning on their sides as they do so. Note the
distinctive color zones, the characteristic shape of the head and beak,
and the smooth lines of the flippers. (_Photo by L. Rigley._)]
[Illustration: Figure 145.--An Atlantic bottlenosed dolphin taken at
Isla La Blanquilla, off Venezuela. Because they inhabit shallow waters,
Atlantic bottlenosed dolphins are infrequent victims of strandings.
(_Photo courtesy of F. Cervigon._)]
[Illustration: Figure 146.--Atlantic bottlenosed dolphins have from 20
to 26 teeth in each side of the upper jaw and from 18 to 24 in each side
of the lower jaw. These teeth, sharply pointed in younger animals, may
wear substantially as the animal ages. (_Photo courtesy of Wometco Miami
Seaquarium._)]
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.
[Illustration: Figure 147.--A Guiana dolphin from Kartabo, British
Guiana. In the coastal portion of its range along the northeastern South
American coast, this species is most likely to be confused with the
Atlantic bottlenosed dolphin. Guiana dolphins are much smaller, rarely
exceeding 5.6 feet (1.7 m), have a more triangular dorsal fin, and tend
to be found more frequently in estuaries and rivers. (_Photo by A. B.
Van Beneden from Zoologica VII(4), by permission of the New York
Zoological Society._)]
[Illustration]
[Illustration: Figure 148.--Guiana dolphins harpooned in Kartabo,
British Guiana. Guiana dolphins have from 26 to 35 teeth in each jaw.
Atlantic bottlenosed dolphins, which are larger but somewhat similar in
appearance, have from 20 to 26 teeth in each upper jaw and from 18 to 26
in each lower jaw. (_Photo by A. B. Van Beneden from Zoologica VII (4),
by permission of the New York Zoological Society._)]
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.)
[Illustration: Figure 149.--Captive rough-toothed dolphins in Japan.
Note the distinctive, smoothly tapering head and the white coloration of
the sides and front of the snout. Rough-toothed dolphins are probably
widely distributed in the offshore waters of the tropics. The streamers
on the backs of the animals are marker tags (see Appendix A.) (_Photo
courtesy of Japanese Whales Research Institute._)]
[Illustration: Figure 150.--Closeups of the highly distinctive head of a
rough-toothed dolphin showing the white lips and the lack of a clear
demarcation between the snout and the forehead. This species has from 20
to 27 fairly large teeth in each side of both the upper and lower jaws.
(_Photos at Sea Life Park, Hawaii, by K. C. Balcomb (top) and S.
Leatherwood (bottom)._)]
[Illustration: Figure 151.--A rough-toothed dolphin stranded near New
Smyrna Beach, Fla. This species has from 20 to 27 fairly large teeth in
each side of both the upper and lower jaws. Those teeth are sometimes
marked by many fine vertical wrinkles along the crown, a characteristic
from which the species derives its common name. (_Photos by D. K.
Caldwell._)]
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