Leatherback sea turtles have existed since dinosaurs roamed the earth, but climate change may now put the future of the species in danger, according to researchers from Florida Atlantic University.
Their recent study – published last month in the Endangered Species Research journal – showed that hatchling morphology, performance and nest success were all influenced by nest temperature.
“Increasing sand temperatures can affect embryonic development, which can lead to decreased hatching success and hatchling performance,” said the university. “Hatchlings need to be in good physical shape to crawl from the nest to the water to avoid being preyed upon by seabirds, raccoons and other predators.”
According to the Florida Fish and Wildlife Conservation Commission, leatherback sea turtles are already listed federally as an endangered species. Apart from climate change and heat, these turtles also face threats such as fishing gear, harvesting of eggs, loss of habitat, ocean pollution, marine debris and more, per National Oceanic and Atmospheric Administration Fisheries.
“One of the most unique of all sea turtle species, the leatherback (Dermochelys coriacea), is distinguished by its smooth, ‘leathery’ looking carapace or shell,” said Florida Atlantic University.
This rubbery shell is made of fatty tissue, tiny bones and a thin layer of skin. They appear black with blue, pink and white splotches and they can grow to be five to six feet long and weigh from 500 to 2,000 pounds, making them the largest sea turtles in the world.
In the U.S., leatherbacks can be found in Florida and Alaska. They can also be found in marine waters throughout the Atlantic, Pacific and Indian Oceans. Known as deep-divers, the leatherback’s diet consists mostly of jellyfish and salps.
Results of the recent study found that mid- and late-season leatherback hatchling masses differed significantly from each other. Mid-season hatchlings weighed more.
“For the study, temperature data loggers were placed in 13 leatherback turtle nests along 9.6 kilometers of coastline in Juno Beach on the day they were laid during the early, middle and late South Florida nesting seasons beginning in March and ending in June,” said the university. “Researchers looked at the relationship between nest incubation temperatures and hatching success, emergence success, hatchling morphology and locomotor performance.”
Once they emerged, the hatchlings were tested on their ability to flip over when placed on their backs and for how fast they could crawl. Researchers also measured the hatchlings and monitored the temperature of their nests.
“Nests with lower temperatures produced longer hatchlings; the highest nest temperatures produced hatchlings with thicker body depths,” they explained. “Flipper length also correlated with temperature. Hatchlings from the highest nest temperatures had shorter flippers compared to hatchlings from mid-season nests that had longer flippers.”
Those aren’t the only things that were different based on temperature. Hatchlings from hotter nests had significantly lower scores on the tests measuring their ability to turn over. Hotter nests also had a short incubation period, meaning a shorter amount of time for embryos to develop, leaving them “unable to convert as much of the yolk mass to body tissue growth.
“Interestingly, locomotor performance did not show the same correlations with temperature as hatching and emergence success, indicating hatchlings can be good performers even if they come from nests with poor hatching and emergence success,” said Sarah Milton, senior author and chair and professor, Department of Biological Sciences within FAU’s Charles E. Schmidt College of Science.
In addition to leatherbacks, the five other sea turtle species are also protected by the Endangered Species Act, according to the United States Geological Survey. At the same time, global temperatures have been steadily rising since 1880, per NOAA data.