only about one-sixth of the body length, while those of the
Atlantic pilot whale may be one-fifth the body length or more. Note the
length of the flippers of the pilot whale in the background, relative to
its overall length. (_Photo from South Carolina by J. G. Mead._)]

GRAMPUS (T)

_Grampus griseus_ (G. Cuvier 1812)

Other Common Names

Risso's dolphin, gray grampus, white-headed grampus, mottled grampus,
Risso's porpoise, hard knocks (St. Vincent), white blackfish (Cape Cod).

Description

Grampus reach a maximum length of about 13 feet (4 m). The body is
robust, particularly in front of the dorsal fin, and lacks a distinct
beak. The head is somewhat bulbous and is marked on the front by a
V-shaped crease with the point downwards, which divides the melon into
two parts. The flippers are long and pointed on the tips. The dorsal
fin, located at about the midpoint of the body, is tall, to 15 inches
(38.1 cm) or more, and distinctly falcate. The body narrows rapidly
behind the dorsal fin and the tail stock is quite narrow. The flukes are
broad, concaved on the rear margin, and deeply notched.

The bodies of grampus are a uniform light gray at birth. As the animals
age, their color darkens to almost black with distinctive regions of
grayish white on the belly and chest. The body of older adults is cream
white or silver gray, particularly on the head, with numerous scars,
presumably from encounters with other grampus and perhaps with the
squid, which are one of the species' major food items.

The flippers, dorsal fin, and tail flukes usually remain dark even in
adults.

Natural History Notes

Grampus are found in herds of up to several hundred individuals and may
be seen "porpoising" (leaping from the water) as they surface to
breathe, and breaching. They sometimes ride the bow waves of a boat.

Grampus feed on fish and squid.

May Be Confused With

From a distance grampus are most easily confused with Atlantic
bottlenosed dolphins. They may be most readily distinguished by the
following differences:

ATLANTIC BOTTLENOSED
GRAMPUS DOLPHIN

SIZE

To 13 feet (4 m). Rarely to 12 feet (3.7 m);
usually less than 10 feet
(3.1 m).

BODY COLOR

Young are uniform light Dark gray on body; lighter
gray; older animals dark gray on