“Did you know that sea turtles on reaching the age of sexual maturity know to go back to the same exact beach – where they once emerged as hatchlings – and lay eggs?” Amy Bonka asked a crowd of about 35 students, faculty members and community members Jan. 9 at Ghost Train Brewing Co.

Her love for the animals she studies was evident as she continued to share her knowledge with those in attendance.Bonka, a Ph.D. student at the University of Alabama at Birmingham, studies early life behavior of the world’s two most endangered species of sea turtles – the Kemp’s Ridley and the Western Pacific Leatherback. She aims to help sea turtle conservation programs improve their practices through her research techniques.
thumbnailBonka presented her research as part of UAB Graduate School’s ‘Discoveries in the Making’ series.

Having lived near the beach while growing up in Florida, Bonka was always interested in marine biology and marine conservation programs, which led her to pursue a bachelor’s degree from UAB in marine biology.

She was first introduced to sea turtles while doing her undergraduate research in Dr. Thane Wibbels’ lab. She then visited some of the nesting beaches in Florida where she witnessed the nesting turtles. Bonka’s interest in the animal continued to grow through two internships in her last year of undergraduate study. One was at the Florida Aquarium in Tampa and the other at Mote Marine Laboratory and Aquarium in Sarasota, Florida. At Mote, Bonka helped the lab’s veterinarians treat sea turtles that were injured, stranded, unresponsive or needed surgery.

“Oftentimes, a sea turtle that underwent a surgery would stop bleeding as soon as it is placed back in water,” Bonka said. “Facts like these helped kick start this heavy interest in sea turtles.”

With a desire to learn more about the biology of the species, Bonka worked at two conservation programs – one at the Rancho Nuevo beach along the Gulf of Mexico, where the majority of all Kemp’s Ridley sea turtles nest, and another at the Bird’s Head peninsula in Papua Barat, Indonesia which is home to the Western Pacific Leatherbacks.

She worked at Rancho Nuevo for three nesting seasons and, as a result, had many scientific questions about the hatchlings’ emergence and orientation behaviors, and their swim and crawl speed. She was also interested in finding how the fitness of the hatchlings affected the efficiency of the two behaviors.

Her research, in part, needed to determine how and when the hatchlings emerged from the nest. Bonka hypothesized the hatchlings were developing an internal clock within the nest to determine the appropriate time of emergence from the nest. Unlike a physical clock, it is one that is derived from cues like fluctuations in beach and nest temperatures. To test this, she used temperature and vibration sensors within the nest, and infrared time lapse wildlife cameras above the nest to capture the emergence path in multiple nests.

“The built-in internal clock developed from the temperatures allows the hatchlings to generally emerge prior to sunrise, and it could possibly allow hatchlings to avoid predators and hot temperatures,” Bonka said. “Metal meshes were placed around every nest to contain the emerged hatchlings.”

To test the same hypothesis in the lab, Bonka will use Red-eared Slider turtle – a semiaquatic turtle – as a model organism for Kemp’s Ridley. She will test if fluctuating the temperatures can serve as cues to time their emergence from the nest and affect their fitness.

At Rancho Nuevo, Bonka also noticed varying orientation patterns in the hatchlings. After emerging from the nests, some of the hatchlings were directed toward the ocean while others were meandering and did not reach the ocean. She found the difference in these two movements were related to the survival of the hatchlings and wanted to know how the beach topography at Rancho Nuevo might affect the ability of these hatchlings to orient.IMG 7982

There are two distinctive backdrops at Rancho Nuevo – dune, which are hills of loose sand that ranged from 5 to 15 feet tall, and barra, which is flat land that mostly has fresh water lagoons connecting the ocean. She used orientation arenas – a circle with eight interconnecting lines – in both dune and barra locations and observed the hatchlings’ orientation in and around the arena every hour from 5 to 7 a.m. She chose different time frames to test if the amount of natural light available at the time of orientation made any difference in their paths. The metal mesh with contained hatchlings was placed at the center of the arena, and manually removed to observe their orientation.

“Observing the hatchlings orient for about 10 minutes in both locations at three different times, we found that dune locations allowed the hatchlings to orient far more efficiently toward the ocean than the ones at barra,” Bonka said. “Also, sunlight had a small effect on helping the hatchlings find the ocean.”

After 10 minutes, about 25 percent of the released hatchlings at the barra location were still wandering to find the ocean, whereas, at the dune location, only 1 percent of the hatchlings remained lost. After sunrise, at the barra, Bonka found the hatchlings a little more directed but still very meandering.

“One of the reasons why female sea turtles are selecting beaches with these distinctive dune backdrops as locations for nesting could be due to the fact that dune locations enhance the survival of the hatchlings,” Bonka said.

At the Bird’s head peninsula in Indonesia, Bonka was interested in knowing the Leatherbacks’ fitness, especially in relation to nest temperatures, in addition to their emergence behavior. So, she investigated the hatchlings’ crawl speed toward the ocean and initial swim speed on reaching the ocean using drone and stationary game cameras.

“We found that Leatherback hatchlings from Bird’s head peninsula had slower crawl and swim speed than Leatherback hatchlings in other beaches,” Bonka said. “We hypothesized that it may be because of the warm beach temperature.”

Bonka noted further investigation was necessary to confirm her hypothesis about how the Leatherbacks’ fitness can be related to their developmental temperature and, in turn, their survival.

While Bonka’s knowledge of these creatures comes from years of studying them, she said that everyone has a role in protecting the species.

“People who do not necessarily work with sea turtles can help conserve them in other ways, like not using much disposable plastics, which can end up in the ocean,” Bonka said.