News for leatherback populations elsewhere is not so encouraging, however. Populations have plummeted at eastern Pacific nesting beaches in Mexico and Costa Rica, which once hosted thousands of female leatherbacks each year. Extirpation, or local extinction of the species, may be imminent on those beaches.
"The good news here is that while most sea turtles continue to decline, some sea turtles are increasing. We need to understand why they are increasing as much as why they are declining so we can transfer this understanding to other at-risk species, like Pacific leatherbacks," says Crowder.
Stewart, Crowder and their colleagues modeled the 30-year nest counts on Florida beaches using a type of multilevel statistical analysis called Poisson regression, which is frequently used to model counts affected by multiple, often random, factors.
Nest counts are the most reliable way of assessing trends in sea turtle populations because they spend most of their lives in the open ocean, where changes in abundance are difficult to detect.
Stewart is now based at the National Oceanic and Atmospheric Administration's Southwest Fisheries Science Center in LaJolla, Calif., as a National Research Council postdoctoral fellow. Prior to that, she served as a postdoctoral research associate at the Duke Center for Marine Conservation.
|Contact: Tim Lucas|