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Sea
Turtles
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Sea
Turtle, Inc.
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Black
Sea Turtle
(Tortuga Prieta) |
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Chelonia
agassizzii
Family: Cheloniidae
Status: Endangered
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Description |
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This
turtle's common name is derived from the almost black coloration of it's
shell. The upper shell (carapace) is dramatically tear-drop shaped and steep
sided. The narrow part of the teardrop is toward the tail end of the turtle.
The lower shell (plastron) is generally dark gray or gray-green. At one
time, the black turtle was considered to be a race of the green sea turtle.
Some experts continue to list it as such. Like green sea turtles, this species
has a single pair of enlarged prefrontal scales on the head. The head size
is comparatively smaller than that of green sea turtles. There are four
costal scutes on the carapace. Adult black turtles weigh as much as 220
pounds (100 kilograms) and measure up to 39 inches (100 centimeters) in
carapace length. |
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Habitat
and Distribution |
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This
turtle is found primarily in coastal waters, bays and estuaries in tropical
and subtropical latitudes. Iverson (1992) lists the distribution of this
turtle in the eastern Pacific Ocean from southern California, USA to Chile,
west to the Galapagos Islands, Hawaii and Papua New Guinea. According
to Alvarado and Figueroa (1986) the primary nesting beaches of Mexico
include: Colola, Maruata, Mexiquillo, Chimapa, and Motin de Oro.
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General
Information |
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Present
population estimates vary from 5,000 to 10,000 individuals. This turtle
feeds primarily on marine algae. Like most sea turtles, it nests at night.
A typical clutch is approximately 70 eggs. The average female produces 2.5
nests per season. Renesting intervals range from 9-17 days. The eggs typically
incubate from 50 to 55 days prior to hatching. Nest sites are usually on
wide beaches in coves surrounded by rocky granite cliffs. Nesting lasts
about 45 minutes to 1 hours. This includes selecting a site, digging, egg
laying and covering the eggs with sand. Both black and green sea turtles
may dig several nests before laying a clutch of eggs. Sexually maturity
is probably attained between 16 to 25 years of age in this species. Studies
conducted in Michoacan on the nests of black sea turtles reveal that nest
temperatures below 27.1°C produced 0 percent females while temperatures
of 31°C or higher produced only females. Temperature dependent sex determination
(Bull,1980) is comparatively well defined in many sea turtle populations
today. |
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Current
Threats and Historic Reasons for Decline |
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Although
this turtle enjoys a protected status in the Galapagus Islands, some portions
of this population are nesting in coastal Ecuador where they are being exploited.
In Mexico, despite laws to protect them, the turtles continue to be captured
and sold by local Nahuatal people on the black market. According to Alvarado
and Figueroa (1986) offshore poaching with shark gill nets and incidental
capture in shrimp trawls are the main factors contributing to this species
decline. In the 1960s, turtle hide hunting intensified in Mexico as a result
of a ban on the export of crocodile skins to the international markers.
The black turtle is known to hibernate in the Northern Gulf of California
where it is consumed by the indigenous Seri India population. |
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Sea
Turtle, Inc.
(956) 761-4511
Seaturtleinc@yahoo.com
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6617
Padre Boulevard
South Padre Island, Texas
(across from the Tiki)
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P.O.
Box 3987
South Padre Island, TX 78597
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project by Web-Magik.com
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