This male southern elephant seal sports a novel accessory: a cutting-edge sensor that monitors the beast's temperature, along with the depth and salt content of the surrounding water as he swims. The device, which beams the data to a satellite when the seal comes up for air, helps researchers study such large sea predators as they roam Antarctica, going where traditional animal tracking devices such as radio tags would not work. A report in this week's Proceedings of the National Academy of Sciences USA uses the new sensor data to map the routes of multiple seals around the South Pole.