Spotted dolphins are difficult to describe because their size
and colouring vary according to their geographic location. Found
only in tropical waters, and subtropical waters, there are two
recognized species: the worldwide species, the pan tropical spotted
dolphin, Stella attenuata and the Atlantic species, Stenella frontalis.
The spotted dolphin's body is covered with spots and becomes
more densely spotted with age. In the eastern Pacific, coastal
forms are the most heavily spotted, while those found in the Hawai'ian
Islands and in Japanese waters and the eastern Indian Ocean have
moderate spotting. The spotted dolphin has a long slim beak containing
35 to 48 small conical teeth in each side of the upper jaw and
34 to 47 small, conical teeth in each side of the lower jaw.
Color varies according to geographical location, age, and the
individual. Generally speaking, these animals go through five
color phases:
1. Newborn calves are dark grey with a white
belly and no spots;
2. The color changes to two-tone, sharply divided, dark on top,
light on belly and no spots;
3. Adolescent phase when dark spots begin to appear on the lower
part of the body;
4. Light spots appear on the dark upper portion of the body;
5. Dark ventral (underside) spots merge almost into a solid colour
with pink shading on the forward part of the belly
Its beak is black and the lips and tip of the beak are white.
A dark link extends from the middle of the lower jaw to the flipper
and both eyes are circled in black with a black connecting line
from each eye across the beak. The dorsal (top) fin is tall and
curved; the flippers are small and pointed. The flukes are small
and pointed at the tips with a small median notch.
Length averages about 7 feet (2.1 m); weight averages 220 pounds
(100 kg). Calves are 32 to 36 inches (80 to 90 cm) at birth Spotted
dolphins feed on many varieties of fish and squid found near the
surface of the water. In the eastern Pacific, pregnant females
feed more on squid and nursing females tend to feed more on fish.
The reason for this is unknown.
This species reaches maturity between 6 and 8 years of age or
when the animal is about 6.5 feet (2 m) in length. Mating and
calving take place throughout the year; the calving interval is
believed to be about every two years, but in stressed populations
mating takes place at an earlier age and calving at shorter intervals,
a response to the enormous mortalities suffered from being entangled
in nets by the tuna fishery. Gestation is 11 1/2 months and calves
are nursed for 11 months.
These animals are highly social and are sometimes found in herds
of thousands, especially in offshore forms, though groups of several
hundred are more common. Herds contain both sexes and all ages.
Pan tropical spotted dolphins are often seen in the company of
other dolphin species, particularly spinner dolphins.
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