11Leatherback sea turtles travel great distances throughout their lives. Some migrate up to 7,000 miles between their hatching and feeding areas. Females travel even farther, making the return trip to the very beach where they hatched, to lay eggs every two or three years.
Because leatherbacks are highly endangered species, it’s critical to know as much as possible about their nesting habits in order for conservation and management efforts to be successful. A new study from the University of Illinois examines the factors that influence when and where leatherbacks lay their eggs in order to do just that.
Previous studies have looked at the slope of the beach, the type of sand, and other beach- and light-related factors, but no study has looked at what exactly causes a female to dig her nests in a particular spot once she reaches the beach.
To determine those factors, the researchers studied leatherback sea turtles that nest on an island in the West Indies called St. Kitts.
“They don’t nest every year, but when they do nest, they’ll often lay multiple clutches,” University of Illinois veterinary clinical medicine professor Dr. Mark Mitchell said in a news release. “Sometimes they’ll ‘false crawl,’ which means if they’re not happy with something, they’ll go back into the water and come back another time. One of the concerns that we had was that maybe the reason they sometimes leave the beach without laying has something to do with the beach itself.”
The researchers documented the sand, air and water temperatures, humidity, wind speed, cloud cover, lunar phase, tides, and levels of both natural and artificial light. They found that the leatherbacks do exhibit preferences for some spots over others, and some females will start to dig one or two nests before settling on a final location for their eggs.
“They tend to nest in sand with a slightly higher pH and a milder conductivity than sand taken at the same depth from the control sites. The leatherback nests are in a sand that allows itself to be highly compact,” Mitchell said.
“We also saw that the females like to lay when the moon is closer to full and when cloud cover is low, which probably is based on light.”
To learn more:
- Read the Illinois news release: Leatherback sea turtles choose nest sites carefully, study finds
- Read the study abstract: Evaluating Environmental and Climatic Influences on Nesting in Leatherback Sea Turtles (Dermochelys coriacea) in St. Kitts, West Indies
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