Fig. 4. (A) A juvenile green turtle swimming in a magnetic navigation experiment. Turtles were placed into soft cloth harnesses and tethered to an electronic tracking device that monitored their orientation as they swam in a water-filled arena surrounded by a magnetic coil system (Lohmann et al., 2004). (B) Evidence for a magnetic map in green turtles. Juvenile turtles were captured in feeding grounds near the test site in Melbourne Beach, Florida, USA. Each turtle was exposed to a magnetic field that exists at one of two distant locations along the coastline (represented by stars). Turtles exposed to the field from the northern site swam approximately southward, whereas those exposed to the field from the southern site swam approximately north. Conventions are as in Fig. 2. (Modified from Lohmann et al., 2004.) See text for details.