Climate and Longevity Tied to Loggerhead Turtle Nesting Behavior

New research suggests there is a direct link between climate change and the behavioral patterns of loggerhead turtles during nesting season.

A team from several state and national research organizations discovered that favorable climate conditions in the year or two before a nesting season, coupled with the number of returning nesting female turtles, are strongly related to the number of nests produced by these reptiles in a given year.

"Our study suggests that the cumulative survival from hatchling to maturity, which may take 30 years, combined with present-day climate effects on mature females, has a greater influence on annual nesting population size than does the exclusive impact of survival during the first year of life as hatchlings," said Vincent Saba, a research fishery biologist at NOAA Northeast Fisheries Science Center. "The first year of life represents only 3 percent of the time elapsed through age 31."

While there is often a concentrated effort to protect turtle hatchlings, the study makes a case for the need to protect the loggerhead turtles in the decades leading up to their maturity as well.

The vast majority - nearly 90 percent - of loggerhead turtle nesting in the Northwest Atlantic occurs on the east coast in Florida.

For their study, the researchers used observed nest counts taken between 1989 and 2012 to model the importance of first-time nesting turtles - age 31 - to future nesting numbers. Future nesting numbers were determined by a projection derived by the estimated number of hatchlings produced between 1989 and 2012.

Although there was a decline in annual next counts in the decade between 1998 and 2007, the projections did not reveal a decline in annual nest counts in the decade between 2029 and 2038, which suggests that annual nesting variability and trends are influenced more by returning nesters than by first-time nesting turtles.

The researchers suspect climate may also play a role in a successful nesting season for loggerhead turtles. Changes in climate may result in turtles having variability in their annual energy consumption at foraging areas in the year prior to nesting.

"This study offers a different perspective than earlier work that suggested most of the annual variability in loggerhead sea turtle nest counts in Florida between 1989 and 2010 could be explained by climate forcing on hatchling survival," Saba said. "We reached a much different conclusion. The annual variability and trends in loggerhead nesting numbers in Florida are associated with long-term survival at sea from hatchling to maturity, combined with climate-driven changes in mature female foraging areas within a year or two before nesting."

The research is published in the journal PLOS One.