New paper says incubating Kemp's ridley sea turtle eggs at Padre Island is key to population growth/NPS file

Kemp's ridley sea turtles, the most endangered sea turtles in the world that are far from reaching population numbers to downlist them under the Endangered Species Act, would benefit from continued incubation of hatchling eggs at Padre Island National Seashore on the Gulf of Mexico in Texas, according to a new paper.

The paper, which appears in the August issue of Ecosphere, comes amid controversy over the Sea Turtle Science and Recovery Program at Padre Island. Four years ago a draft National Park Service paper examining the program run by Dr. Donna Shaver said the program had gotten unwieldly and too costly at roughly $1.9 million per year. Within 3-5 years, the review added without any detail, the program would be unsustainable. As a result, it should be tightly reined in, the report recommended.

Read what the Park Service's review concluded.

Public Employees For Environmental Responsibility questions whether the Park Service is strengthening the turtle program.

However, the sea turtle program that focuses on removing turtle eggs from their nests and incubating them to birth has demonstrated success in contributing to Kemp's ridley populations and producing offspring with an affinity for Padre Island, according to the findings mentioned in the paper, "Quantifying the effects of nest management and environmental change on demography of an endangered sea turtle."

A Satellite Population

In the 1980s the national seashore, which runs not quite 70 miles along the Gulf Coast and is the largest stretch of undeveloped barrier island in the country, was specifically chosen by international experts to develop a satellite nesting population of Kemp's ridley turtles that could both contribute to global recovery and serve as a backup population in case a disaster hit the Mexican populations, which are largely centered around Playa de Rancho Nuevo at Tamaulipas.

Too, the Padre Island work was seen as a way to develop protocols for a captive breeding program, if ever needed.

Last year Padre Island National Seashore staff raised the question of whether a formal beach management plan was needed. Part of that question considered the role the Park Service has played with Kemp's ridley turtles, which has focused on recovering eggs from nests, incubating them, and then releasing the hatchlings into the Gulf of Mexico.

The management plan under consideration lays out the following four possible scenarios for the program, although none are set in stone, and public suggestions for other alternatives have been encouraged:

• Potential Pilot Study 1: In-situ nesting – can predation be reduced without moving eggs? Test predation mitigation measures for effectiveness in the protection of Kemp’s ridley sea turtle nests at the Seashore. Study areas would be Malaquite Beach and/or near the research cabin.
• Potential Pilot Study 2: Does moving nests protect them from inundation, or flooding? Inundation, or flooding, of nests can kill the eggs, depending on how long the nest is under water. Would relocating the nests higher on the beach improve chances for survival? This measure has been successful elsewhere for other sea turtle species. Study areas would be Malaquite Beach and/or near the research cabin.
• Potential Pilot Study 3: Remove or reduce NPS vehicles from Malaquite Beach, except for emergency use. Malaquite Beach is closed to visitor driving. NPS staff drive here, potentially impacting wildlife and visitor experience. Would reducing NPS vehicle use improve the visitor experience and better protect sea turtles, in-situ nests, and other wildlife? Exceptions would be allowed for emergencies.
• Potential Pilot Study 4: Would unmanned aerial vehicles or other video technology be effective monitoring for nesting sea turtles?

Benefits Of Managing Kemp's Ridley Eggs

The new paper, authored by U.S. Fish and Wildlife Service scientists Beth E. Ross, Matthew A. Boggie, Angela Anders, and Shaver from the Park Service, concludes that continuing the practice of incubating Kemp's ridley eggs would lead to "stable or increasing population growth rates," whereas leaving them in place on the beaches would lead to "stable or decreasing population growth rates as well as a probability of extirpation from Texas."

According to the National Marine Fisheries Service, the numbers of Kemp's ridley nests in the Gulf of Mexico has fallen since 2010, when 12,377 nests were counted on the three primary nesting beaches — Rancho Nuevo, Tepehuajes, and Playa Dos in Mexico — and they produced 663,614 hatchings. By 2014, the number of nests had dropped to 10,987 and the number of hatchlings to 519,273.

"The number of hatchlings released from Rancho Nuevo, Tepehuajes, and Playa Dos, Mexico, beaches has exceeded 300,000 each year since 2002, and was over 1 million in 2009, but dropped to about 520,000 in 2014, due to fewer nests," the agency said in 2015 in its last five-year status review of the species.

At Padre Island, nesting rates have slightly declined, but not at the same level, according to the new paper.

"From 1994 to 2014, a total of 1,661 nests were managed that yielded 156,345 eggs and 130,523 hatchlings. From 2015 to 2021, 1,597 nests were monitored, resulting in 150,726 eggs and 127,490 hatchlings," the authors noted.

At the same time, they found that the "abundance of all adult Kemp’s ridley sea turtles (breeders and nonbreeders from Texas and immigrants from outside Texas) increased throughout the study. The number of breeding immigrants in the population increased to a peak in 2009, while the number of breeders and nonbreeders from Texas increased until 2018 and did not statistically change from 2018 to 2021."

Their statistical conclusion was that "a continuation of nest management practices would have the highest probability of a stable or increasing population in the future. As the protection involved in future nest management scenarios decreased, the probability of a stable population compared to current management also decreased, but the mean population growth rate was still higher than the no-management scenario (i.e., leaving all nests in situ)." 

"Due to lower survival, increased temperatures, and sea level rise, scenarios based on leaving all nests in situ resulted in a higher probability of extirpation of the species from Texas, with greater than 70% probability of extirpation in some scenarios," they added.

They also found that "while females nesting on Texas beaches were largely immigrants from the Mexico population until around 2010, the number of breeding females born in Texas has been increasing and is currently similar to the number of immigrants."

Far From Recovered

Under the Marine Fisheries Service guidelines, to downlist the Kemp's ridley turtles from "endangered" to "threatened" there would need to be a population of at lesat 10,000 nesting females in a season across the three Mexican beaches. In 2014, the number of nesting females at those beaches was approximately 4,395, the agency says.

A criterion for completely removing the species from Endangered Species Act protections is that there be 40,000 nesting female per year over a six-year period, a level that had been expected to be reached this year.

"An unprecedented mortality in subadult and adult females post-2009 nesting season may have altered the 2009 age structure and momentum of the population, which had a carryover impact on annual nest numbers in 2011-2014," the five-year status review said. "The results indicate the population is not recovering and cannot meet recovery goals unless survival rates improve."

A possible factor influencing the nesting decline, though one the Marine Fisheries Service said was "still under evaluation," was the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

The bottom line of the five-year status review was that Kemp's Ridley sea turtles are a species "whose extinction is almost certain in the immediate future because of a rapid population decline or habitat destruction, whose limiting factors and threats are well understood and the needed management actions are known and have a high probability of success, and is a species that is in conflict with construction or other developmental projects or other forms of economic activity."