|The Mammals of Texas -
Cetacea : Family Delphinidae : Stenella
Description. These are small dolphins
that average less than 1.8 m in length and 75 kg in
weight. Maximum size is about 2.1 m and 95 kg. These
dolphins are very slender and have a long, slender beak
that is black above and white below. Coloration is dark
gray dorsally fading to lighter gray on the sides and the
belly is white. A dark stripe extends from the flipper to
the eye. Average total teeth, 224, is greater than for
any other Texas cetacean.
Distribution in Texas. Worldwide
in tropical and warm temperate waters. Known in Texas
from strandings along Padre Island National Seashore.
Habits. Spinner dolphins derive
their name from a habit of leaping from the water and
warping their bodies into graceful curves, or spinning
lengthwise before splashing back. The motives for this
behavior are not known but such actions are often in
themselves enough to distinguish this species.
They usually occur in groups of 30 to
several hundred but may number into the thousands.
Spinner dolphins feed on mesopelagic fishes, squid, and
Adult females give birth to a single
calf at 2-year intervals. Parturition usually occurs in
early summer but can occur in any season. Their period of
gestation is 11 months and calves are about 75 cm long at
Spinner dolphins have mass stranded
twice in the Gulf of Mexico. One stranding of 36 animals
occurred on Dog Island, Florida, in 1961, and the other
was near Sarasota, Florida, in 1976. The latter stranding
involved 50-150 spinners that beached themselves at
several points during an extremely low tide. The dolphins
came ashore with much "squealing and crying"
but this later subsided and the animals were quite
passive on the beach. Several of the animals were
returned, apparently successfully, to the sea; however,
others merely stranded again and at least 10 died.
In the eastern tropical Pacific this
species is often caught and drowned in large numbers by
the tuna fishing industry. Over the last 20 years the
total population in those waters has declined about 80%,
from 2 million to 400,000, due to incidental catch. Gulf
of Mexico populations do not receive this pressure, but
data for population estimates are unavailable and
population trends are not known in Gulf waters.
Illustration credit: Pieter