Of the seven species of sea turtles in the world, the Kemp’s ridley, Lepidochelys kempii, is the most endangered. It is also the smallest sea turtle and the only species that nests primarily during the daytime.
In 1978, a collaborative bi-national program between Mexico and the United States was developed to try and restore this species’ population to a self sustainable level, and in 1981, the U.S. Fish and Wildlife Service asked the Gladys Porter Zoo to administer the United States’ field portion of the joint U.S./Mexico effort to protect and increase the production of Kemp’s ridley sea turtles in their natal beaches located in the State of Tamaulipas, Mexico. To date, the Zoo still carries out that role.
Sea turtle research and conservation in Mexico was formalized in 1962 with Instituto Nacional de la Pesca (INP) then named Instituto Nacional de Investigaciones Biologico-Pesqueras (INIBP) being the lead agency. Conservation efforts for the Kemp’s ridley were initiated in 1966; when the National Program for Research and Conservation began. The project field station was located on the beach near the ranching community of Rancho Nuevo, in the municipality of Aldama, Tamaulipas. This locale is the only one in the world where massive nesting aggregations of this sea turtle were and are known to occur. Because it is the only known major nesting beach for the Kemp’s ridley, this beach was declared the first National Reserve for the Management and Conservation of Sea Turtles in Mexico on July 4, 1977.
Historically speaking, the population of the Kemp’s ridley sea turtle declined at an alarming rate from the 1940’s to the 1980’s. A film made in 1947 by Andres Herrera, an engineer from Tampico, Tamaulipas, was presented by Dr. Henry Hildebrand of the University of Corpus Christi, Texas, to the American Society of Ichthyologists and Herpetologists in 1961 at their annual conference. The film, fourteen years old at the time, revealed an estimated 40,000 female Kemp’s ridleys nesting on the beach at one point in time. This was the first time scientists had observed this type of massive synchronized nesting behavior. This extraordinary phenomenon is termed “arribada” or “arribazon” in Spanish. It has two literal translations; “great arrival”, and “to put into port under stress”, either of which is equally appropriate in this case. What could have appeared more stressful than thousands of these turtles clambering over one anothers’ shells with flippers flailing and sand being tossed high into the air in every direction? Many females actually excavated the eggs off those that preceded them. The result was that L. kempii was its own worst “predator” at that point in time. That, needless to say, was soon to change.
From 1966 to 1987, conservation efforts focused on the area of Rancho Nuevo with the camp located first at Barra Calabazas and then at Barra Coma where it presently exists. In 1978, the U.S. joined with Mexico at Rancho Nuevo. In 1988, the program, now a bi-national one, expanded to the south to Barra del Tordo with a camp at Playa Dos. In 1989 a third camp was established to the north at Barra Ostionales on Rancho Los Pericos. The north camp’s location was changed to 10 kilometers north of its original location, near the town of Tepehuajes, in 1996 for logistical reasons. In 1996, in coordination with the Tamaulipas State Government, as in Tepehuajes, a camp was established in La Pesca. In that same year, CRIP Tampico and CetMar No. 9, as well as API Altamira, also expanded the project to include Playa Miramar in Ciudad Madero and Playa Tesoro in Altamira. In 1997, the area of Lechuguillas, municipality of Vega de Alatorre, Veracruz, started to be protected in cooperation with CRIP Veracruz.
Over the last twenty-eight years, the Mexican and U.S. biologists working with the Kemp’s ridley sea turtle have learned a lot about the biology of nesting sea turtles. When the project began, it basically was at ground zero. We now know that although some turtles nest in consecutive seasons, the majority of them nest every other year. We know that nests average 2.6-3.0 per female per season, each clutch being one hundred or so eggs which require 42-62 days incubation, depending on the temperatures. The Kemp’s ridley begins nesting around the second week in April.
We have now verified turtles which were originally tagged on the eastern seaboard of the U.S. as having returned to Mexico to lay their eggs. We have recorded experimentally head-started turtles nesting on Padre Island National Seashore, USA, and the same turtles at Rancho Nuevo in Mexico during the same nesting season. Apparently, the experimentally imprinted head-started turtles were able to navigate to Padre Island National Seashore and were also able to socially facilitate with wild ridleys returning to the Tamaulipan coastline’s historic nesting grounds.
Kemp’s ridley turtles will return to nearly the same spot on the beach where they nested in previous seasons; however, if they are disturbed, they possess the behavioral “plasticity” to move several kilometers up or down the beach to a new nest site.
In past years we were unaware that a few ridleys do nest at night even though the norm for this species is diurnal (or daytime) nesting. Our first beach patrol or “recorrido” as it is called in Spanish, began at 8:00 am C.S.T.; for years and years and that was early enough to find the first nesting turtles of the day. Starting in 2001, our first beach patrol began encountering crawls (tracks) and nests which were apparently from late in the afternoon of the previous day or perhaps the night time or early morning hours. The first and last “recorridos” kept being moved to an earlier and later hour respectively, and eventually, nesting turtles (or the nests) were found at 5:30 am during the cover of darkness and as late as 8:30 pm. This has caused us to readjust our thinking and our patrol schedules.
The United States field assistance group, along with the Mexican Federal and State Government crews, under the supervision of trained sea turtle biologists, aid in beach patrols. Relevant data are recorded and subsequently, most of the egg clutches are translocated to facsimile nests within protective corrals.
Two auxiliary corrals have been used on the Rancho Nuevo beach since 2002. One is located to the north at Barra Carrizo and the other was constructed to the south at kilometer marker 5.1. The corrals were constructed to facilitate the quick disposition of the nests and to relieve the pressure at the main corral at Rancho Nuevo. Patrols at the north and at the south part of the beach would quickly transfer the nests to their respective corrals during arribadas, while those patrols nearest the main camp would use the main corral. The auxiliary corrals were built to exclude predators and had tent facilities to house personnel who watched the area at night.
The fact that the fishing industry is working with governmental agencies and environmentalists in both Mexico and the United States is a big step in the right direction and hopefully one which will serve as a model for the other endangered species programs where difficult economic and socioeconomic issues exist. There are still problems, points of contention and difficult issues to be resolved. By working together for a common goal, “a Healthy Gulf of Mexico”, much needed resources may be put where they are needed, and productive, versus and endless array of litigation and mistrust.
Since 1978, there have been over 70k registered nests, and a little over 4.5 million hatchlings have been released into the Gulf of Mexico. At present, nesting aggregations (arribadas), number in the hundreds, not the thousands which are necessary for the species to survive without man’s intervention. Clearly we are going in the right direction but we cannot diminish our present effort if we are to succeed.