With well-mapped roads and satellites, navigation is no longer the technical challenge it was for our forebears. But many other creatures have no need for such navigational aids; with built in compasses and maps, they routinely find their way home. Ken Lohmann and his lab are fascinated by turtle's navigational abilities and have studied hatchling homing for years,but Lohmann knew that many animals' navigational strategies change as they grow older. It's only now that he and Larisa Avens have turned their attention to older loggerhead and green turtles to investigate their navigational abilities (p. 1771).
Collecting juvenile turtles trapped in fishermen's nets, Avens and Lohmann drove the young animals away from their shore homes to the National Oceanic and Atmospheric Administration Laboratory in North Carolina, to see which direction the animals would orient. When placed in a test pool during the summer months, the turtles always oriented towards the area where they'd been captured, implying that they knew where they were in relation to their feeding grounds.
But which direction would the animals choose during autumn, their migration season? Would they still head homewards, or aim towards their southern winter havens? Avens and Lohmann tested the young animals in the pool during October and November. Instead of aiming towards their feeding grounds, the turtles chose a southerly bearing, matching the direction the animals migrate to escape winter.
Having found that juveniles from both species can orient successfully in the lab, the team are now keen to discover which crucial cues keep turtles on the right path.