|The Mammals of Texas -
Pantropical Spotted Dolphin
Cetacea : Family Delphinidae : Stenella
Description. A small dolphin with a
relatively short, black beak, blackish back, grayish
sides, and white underparts; eyes usually encircled with
black rings joined by a black stripe across base of
rostrum; dorsal fin, flipper, and flukes black; the pale
sides and abdomen often covered with small blackish
spots; posterior to the dorsal fin the blackish
upperparts and the flippers often covered with grayish
white dots. Teeth small (diameter at alveolus 2.5-3.0 mm)
and 38-42 in each toothrow. Total length, 1.5-2.0 m.
Similar to S.
frontalis but upperparts
blackish, general size smaller, beak narrower, and the
teeth smaller and more numerous.
Distribution in Texas. Occurs in
the tropical and subtropical oceans of the world. Known
in Texas from three individuals that were beached near
Yarborough Pass on Padre Island during Hurricane Fern in
September, 1971, and two separate individual strandings
near Port Aransas in 1989 and 1990.
Habits. These dolphins are
usually seen in groups of five to 30, although large
herds of 1,000 or more are occasionally observed. Unlike
many other dolphins, groups of pantropical spotted
dolphins do not appear to be segregated by sex and age.
These dolphins feed at or near the surface on fish,
including mackerel and flying fish, squid, and shrimp.
In the eastern tropical Pacific, the
following reproductive data are known. The gestation
period lasts 11.5 months and lactation lasts about 11
months. At birth the calves average 80 cm in length and
at 1 year are 1.4 m long. Males attain sexual maturity at
about 6 years of age while females reach maturity at 5
years. The calving interval is 26 months. No data on
reproductive habits are available for the Gulf of Mexico.
In the Pacific, these dolphins are
killed incidentally in the course of seining for tuna. In
1970, about 400,000 were killed by U.S. vessels alone but
that figure was reduced to 15,000-20,000 by 1978.
Currently, incidental catch is limited by U.S. law to
20,500 per year but is usually lower than that due to
declining tuna seining efforts and the recent adoption of
a porpoise mortality reduction program; this
international agreement by all major tuna seining
countries has a goal of reducing total incidental catch
to less than 5,000 dolphins per year by 1999. In the
Atlantic and Gulf of Mexico, the problem of incidental
catch is limited and was never as great as in the
Remarks. This dolphin was
previously known as Stenella frontalis (Cuvier).
Illustration credit: Pieter