Restoring the Kemp's Ridley Sea Turtle by Donna J. Shaver

 

The first published record of a Kemp's ridley nesting in the wild was an individual found nesting in 1948 at what later became Padre Island National Seashore (PAIS). Although PAIS is the most important Kemp's ridley nesting beach in the U.S., by far most nesting by this species occurs in Mexico. However, for many years, biologists did not know where most of the Kemp's ridley population nested. A Mexican engineer filmed a synchronous nesting emergence of Kemp's ridleys in 1947 at Rancho Nuevo in Tamaulipas, Mexico. Dr. Henry Hildebrand from Corpus Christi, Tex. discovered that film and showed it at a herpetological conference in the early 1960s. Based on this film, the number of turtles nesting at that time was estimated to be over 40,000.

Mexican biologists began studying and protecting the nesting turtles and nests on the beach at Rancho Nuevo starting in the mid-1960s, but they found that the population had plummeted. Despite continuing protection by the Mexican government, by the mid-1980s the population had decreased to an estimated 300 nesting females. This precipitous decline was due primarily to poaching of eggs for use as a supposed aphrodisiac and incidental capture of juveniles and adults by shrimp trawling. As a result of this drastic population decline, Kemp's ridley sea turtle was listed as endangered throughout its range on December 2, 1970, and the species has received Federal protection under the Endangered Species Act (ESA) for the last 40 years.

The purpose of the ESA is to protect and recover threatened and endangered species and the ecosystems they depend upon, so that they ultimately no longer need protection under the ESA. The ESA provided the framework and authority for the U.S. to aid with recovery efforts for this imperiled species. In 1977, a bi-national Kemp's Ridley Recovery Program was formed involving the U.S. Fish and Wildlife Service (FWS), National Marine Fisheries Service (NMFS), National Park Service (NPS), Instituto Nacional de la Pesca of Mexico, and Texas Parks and Wildlife Department (TPWD). As part of this bi-national program, the U.S. joined into the ongoing protection efforts on the nesting beach at Rancho Nuevo. In addition to trying to protect the nesting population in Mexico, another goal of the binational program was to form a secondary nesting colony of Kemp's ridley turtles at PAIS, as a safeguard against extinction in case a political or natural disaster was to occur in Mexico. PAIS was selected as the location for this effort since the nesting habitat is preserved and protected as a National Seashore and it is within the documented historic nesting range of the species.

From 1978 to 1988, more than 22,500 Kemp's ridley eggs were collected at Rancho Nuevo, packed in North Padre Island sand, and transported to PAIS for hatching. The hatchlings were released on the PAIS beach, allowed to crawl into the surf, and captured using aquarium dip nets after a brief swim in the Gulf of Mexico. It was hoped that this exposure to Padre Island sand and surf (termed "experimental imprinting") would cause the turtles to return to PAIS to nest when they reached adulthood. The captured hatchlings were transported to the NMFS Laboratory in Galveston, Tex., where they were reared in captivity for 9 to 11 months. This "head-starting" allowed the turtles to grow large enough to be tagged for future recognition and avoid most predators after release. Finally, the one-year-old turtles were released permanently, most into the Gulf of Mexico off Mustang and North Padre Islands.

PAIS began patrols to find and protect nesting Kemp's ridleys and their eggs on North Padre Island in 1986. Patrol programs began later on other Texas beaches, and today patrols are conducted to some extent on all Texas Gulf of Mexico beaches annually, from April through mid-July. The six patrol programs in Texas are administered by Texas A&M University-Galveston, U.S. Fish and Wildlife Service, ARK, NPS, and Sea Turtle, Inc. Hundreds of dedicated staff members and volunteers conduct these patrols with the support of several organizations such as TPWD. Sea Turtle Restoration Project sponsors a toll-free telephone number (1-866-TURTLE5) to report nesting and stranded sea turtles in Texas.

Patrols are conducted primarily during daylight hours since Kemp's ridleys nest mostly during the day. Most nests are found by the sea turtle monitoring patrols, but some are found by other individuals working or recreating on the beach, especially in the developed areas of the coast. Eggs from nests found on PAIS and northward in Texas are transported either to the PAIS incubation facility or protected enclosures on the beach called corrals and the resulting hatchlings are released at PAIS, to help reinforce the bi-national effort to form a secondary nesting colony there. Eggs from South Padre Island are brought to a protective corral on South Padre Island for incubation, and the emerging hatchlings are released nearby. The public is invited to attend many of the hatchling releases held at PAIS and on South Padre Island, free of charge.

Texas waters also provide very important habitat for Kemp's ridley turtles. Kemp's ridleys forage in Texas Gulf of Mexico and bay waters at various stages of their life cycle. Adult males and females feed in nearshore Gulf of Mexico waters, and a large portion of the adult female population uses these waters as a migratory corridor between foraging grounds in the northern Gulf of Mexico and nesting beaches in Mexico and Texas.

The Kemp's Ridley Sea Turtle Recovery Plan not only focuses on protection of the turtles on nesting beaches, but also in their marine habitat where these turtles spend the majority of their lives. This is addressed through the requirement of shrimp fishery to use turtle excluder devices (TEDs) to prevent incidental capture. Shrimping closures established by TPWD during the Kemp's ridley nesting season in Texas have also been extremely beneficial to the conservation of the species, while at the same time allowing shrimp to grow to a larger, more valuable size prior to market.

Several other recovery task priority items are also outlined in the Kemp's Ridley Recovery Sea Turtle Plan. One of these is operation of the Sea Turtle Stranding and Salvage Network. Many groups and individuals help find and document sea turtles stranded (washed ashore, alive or dead) in the U.S. and Mexico. Live stranded turtles are transported to rehabilitation facilities to receive care, with the objective of returning as many of those turtles as possible to the wild so that they can contribute to the population.

After years of effort from multiple agencies and Federal protection under the Endangered Species Act, Kemp's ridley nesting has increased substantially from the population low of only 702 nests world-wide in 1985. A record 209 nests were recorded in Texas (including 106 at PAIS) and nearly 22,000 in Mexico during 2012. Some turtles from the experimental imprinting and head-starting project have been confirmed nesting in the wild, mostly on North Padre and Mustang Islands. They have contributed to the increase in nesting in Texas during recent years, but by far most nests found in south Texas are from turtles from the wild stock that are repopulating the area.

The substantial growth of the Kemp's ridley population is encouraging. The Kemp's ridley population can be down-listed to threatened status after a number of milestones outlined in the Kemp's Ridley Sea Turtle Recovery Plan are met. One of those milestones is 10,000 females nesting in a season. It will take more years to achieve this goal since each nester produces 2.5 to 3.0 nests within a season, and the rate of nesting increase has noticeably slowed since 2009. In order to continue to make progress towards population recovery, the ultimate goal of the ESA, conservation efforts in Mexico and the U.S. must continue.

Donna J. Shaver is Chief of the Division of Sea Turtle Science and Recovery for the National Park Service at Padre Island National Seashore near Corpus Christi, Texas.

References:

National Marine Fisheries Service, U.S. Fish and Wildlife Service and SEMARNAT. 2011. Bi-National Recovery Plan for the Kemp's Ridley Sea Turtle (Lepidochelys kempii), second revision. National Marine Fisheries Service. Silver Spring, MD 156 pp. + appendices.

Shaver, D.J. 2005. Analysis of the Kemp's ridley imprinting and headstart project at Padre Island National Seashore, Texas, 1978-88, with subsequent Kemp's ridley nesting and stranding records on the Texas coast. Chelonian Conservation and Biology 4(4):846-859.

Shaver, D.J. and C. Rubio. 2008. Post-nesting movement of wild and head-started Kemp's ridley sea turtles (Lepidochelys kempii) in the Gulf of Mexico. In: Endangered Species Research 4:43-55.

Shaver, D.J., K. Hart, I. Fujisaki, C. Rubio, A.R. Sartain, J. Pena, P.M. Burchfield, D. Gomez Gamez, and J. Ortiz. 2013. Foraging area fidelity for Kemp's ridleys in the Gulf of Mexico. Journal of Ecology and Evolution doi: 10.1002/ece3.594.

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