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.
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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)._)]
[Illustration: 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._)]
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).
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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 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).
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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._)]
[Illustration: 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)._)]
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.
[Illustration: 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)._)]
[Illustration: 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)._)]
[Illustration]
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