Loggerhead sea turtles nesting earlier due to warmer ocean temperatures

Loggerheads along Florida’s Atlantic coast are laying eggs 10 days earlier than 15 years ago, UCF research shows

Loggerhead sea turtles along Florida’s Atlantic coast are laying their eggs about 10 days earlier than they did 15 years ago, a change that a University of Central Florida researcher believes was caused by global warming.

John Weishampel, an associate professor of biology, found that as the near-shore ocean temperatures increased by nearly 1.5 degrees Fahrenheit from 1989 to 2003, the median nesting dates for loggerheads gradually became earlier. In 2003, half of the turtles’ nests were laid before June 19, compared with before June 29 in 1989.

The earlier nesting dates raise several questions that need to be addressed in future studies, Weishampel said, including whether the turtles’ food supplies — crabs, shrimp and other invertebrates — will be as plentiful earlier in the season and whether the hatchlings are less likely to survive if they are born earlier.

Additional studies, which will be conducted by UCF and other agencies, could lead to recommendations that governments change some of their regulations to protect sea turtles, Weishampel said. Loggerheads are classified as a threatened species by the federal government.

“Some of the management practices that have been in place — such as lights out at certain times of the year and whether or not you’re allowed to drive on the beach during certain times of the year — could be affected,” Weishampel said.

The turtles’ fertility and the ratios of male to female hatchlings also could be affected by earlier nesting. The sex of hatchlings depends on the temperature of the sand.

Weishampel and two UCF colleagues, biology professor Llew Ehrhart and research associate Dean Bagley, analyzed data from about 25 miles of beaches in Brevard and Indian River counties where thousands of loggerhead turtles nest every year. About 25 percent of loggerhead nests in the United States are on that stretch of beach between Sebastian Inlet and the southern boundary of Patrick Air Force Base.

From 1989 to 2003, the average near-shore ocean temperature in May in that area increased from 76.3 to 77.7 degrees Fahrenheit, or from 24.6 to 25.4 degrees Celsius. An increase of that size is significant enough to affect animal behavior such as nesting and migration habits.

The UCF researchers’ findings follow other studies showing that many species of birds are laying their eggs earlier in the year and that some flowers are blooming earlier as temperatures become warmer.

Weishampel, Bagley and Ehrhart presented their findings in late February at the International Sea Turtle Symposium in Costa Rica. Their findings also will be published in the journal Global Change Biology.