Predation on Loggerhead Turtle Hatchlings after Entering the Sea

Sea turtle hatchlings emerge from nests on ocean beaches, crawl to the surf, enter the ocean and swim rapidly out to sea. Although predation on hatchlings in nearshore waters is presumably high (Stancyk, 1982), few studies have documented this predation rate. Relationships between predation on hatchlings and hatchling activity patterns also are poorly understood. For example, the tendency of hatchlings to leave the nest and enter the ocean at night (Witherington et al., 1990) may be influenced in part by predation. Increased activity of diurnal predators and increased visibility of hatchlings in the water may make newly emerged hatchlings more susceptible to predation during daylight. No studies have systematically compared sea turtle hatchling survival at sea during different times of the day. The goals of this study were to: (1) quantify the rate of predation on loggerhead turtle hatchlings (Caretta caretta) at sea; (2) compare predation rates among hatchlings entering the ocean during the day and at night; and (3) evaluate two separate methods for tracking hatchlings as they swim from shore into deeper water. Our observations span a narrow, but crucial, period of time during hatchling migration, namely, their travel through the presumably predator-rich, shallow waters near shore.