One of the many threats loggerhead sea turtles face is man-made pollution, but the extent of the risk is a question. To begin to look for the answer scientists have measured contaminants in the blood of a group of adult male turtles and tracked their migration along the Atlantic Coast.

The group, led by Jared M. Ragland, a graduate student at the College of Charleston, in Charleston, S.C., captured 19 loggerheads near Cape Canaveral, Fla., in 2006 and 2007. Group members measured and weighed the turtles, took blood samples, and examined their reproductive systems with testicular biopsies. Then they fitted them with satellite transmitters and released them. Over two months, 10 of the animals traveled north as far as Cape May, N.J., while nine remained near Cape Canaveral.