| Of
the eight species of sea turtles in the world, the Kemp’s
Ridley, Lepidochelys kempii, has been considered the most
endangered. It is also the smallest sea turtle and the only
species that nests primarily during the daytime.
The
Kemp's Ridley nests only in the Gulf of Mexico, mostly on
Mexican beaches. But about 100 nests have been found on
U.S. beaches in recent years.
In 1978,
a collaborative program between Mexico and the United States
was established to monitor and protect the turtles and to
try and restore this species’ population to a self-sustainable
level. In 1981, the U.S. Fish and Wildlife Service asked
the Gladys Porter Zoo in Brownsville, Texas, to administer
the United States' field portion of the effort. To date,
the zoo still carries out that role.
The
success of the Kemps Ridley program has made it a case study
in the environmental literature on endangered species recovery.
In fact, discussion has started on the possibility of delisting
the species within the next 10 years.
Populations
of the Kemp’s Ridley were declining at an alarming
rate from the 1940s to the 1980s. A film made in 1947 showed
an estimated 40,000 female Kemp’s Ridleys nesting
on one beach. This was the first time that this type of
massive synchronized nesting behavior had been documented.
This extraordinary phenomenon is termed “arribada”
or “arribazon” in Spanish. It has two literal
translations: “great arrival,” and “to
put into port under stress,” both of which are appropriate.
Over
the last 28 years, Mexican and U.S. biologists have learned
a lot about the biology of nesting sea turtles. It is now
known that most turtles nest only every other year. There
are about three nests per female per season, each clutch
being one hundred or so eggs which require 42-62 days incubation,
depending on the temperature. Although some nests have been
recorded as early as the first week of March, most Kemp’s
Ridleys begin nesting around the second week in April.
Some
turtles which were originally tagged on the eastern seaboard
of the U.S. returned to Mexico to lay their eggs. Turtles
from batches of laboratory-started juveniles on Padre Island
National Seashore have also nested in Mexico during the
same season. Apparently, the laboratory “head started”
turtles were able to navigate to Padre Island National Seashore
and were then able to interact with wild Ridleys returning
to their historic nesting grounds on Mexico's Tamaulipan
coastline.
Kemp’s
Ridley turtles will return to nearly the same spot on the
beach where they nested in previous seasons. If they are
disturbed, they possess the behavioral “plasticity”
to move a few kilometers down the beach to a new nest site.
In the past years, a few Ridleys have been found at night
even though the norm for this species is diurnal (or daytime)
nesting.
While
the number of registered nests fluctuates between seasons,
the number of released Kemp’s Ridley hatchlings from
the six major camps in Mexico has been climbing fairly steadily
since 1996, and 2007 saw a record of 15,032 registered nests
and more than one million hatchlings.
Year |
Hatchlings |
1996 |
119,196 |
1997 |
149,567 |
1998 |
183,920 |
1999 |
227,040 |
2000 |
395,150 |
2001 |
317,127 |
2002 |
402,969 |
2003 |
476,138 |
2004 |
500,767 |
2005 |
630,737 |
2006 |
782,319 |
2007 |
1,023,675 |
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