Wandering around in the brisk morning sunshine and watching the visiting ducks and geese, started me wondering about migration and sense of direction. Having got used to my car’s GPS system telling me to turn around as soon as it is convenient after my strong sense of direction overrode its instructions, I know more is involved than just the position of the sun and what street signs say. Clearly with the sun, a wristwatch and a compass, we should be all set to go anywhere, and like all guys, no need to ask for directions.
Even our goose friends’ travels seem to pale against those of swallows and Monarch butterflies. So what do they use? An internal compass as a directional aid has long been suggested but they are all short of a wristwatch and sextant. It took us a very long time to tame the problem of longitude.
Now, baby loggerheads emerge from their sand nest and rush down to the sea, eager for the wild Atlantic, and knowing exactly where the action is regardless of which side of the Atlantic they start from. Lohmann et al (1) have demonstrated that they work using the Earth’s magnetic field as their direction finder. The mechanism is that they detect both the local intensity as well as the inclination, so they have a 3-D map of magnetic hills and valleys in their mind and, continuing the visual simile, their magnetic sensor, like a magnetic eye, ‘sees’ where they are on the map.
Wonderful as this is, even more remarkable is the fact that they hatch with the map already in place. Learned direction finding seems logical, so salmon tasting their way back to their original river seems plausible but a magnetic map of the North Atlantic carefully packed away by your Mom in a pocket of your genes is something else indeed.
It leads one to wonder what potential latent ability to detect and know our surroundings are being ignored as we turn on our GPS. Clearly the artifice, beloved of authors and screen writers, of people wondering around in circles in the desert or snowy waste, as shown by finding their own footprints, is a fiction. We all have a better idea of where we’re heading than that. But we can still go badly awry, as shown by Mao with his Long March, or Moses with his even longer one. Could we learn to be turtles if we get in closer touch with our inner selves?
1. http://www.cell.com/current-biology/fulltext/S0960-9822(11)00113-8#ResultsandDiscussion
When GPS recommends that people turn the wrong way on a one way street, or (in amazment) off of a cliff, I would opt for the loggerhead's navigational sense ANY day! Here's to the inner turtle!