Rodent roadmaps

If you hate asking people for directions, you might consult a wood mouse instead. Scientists now know how wood mice navigate so well through open fields. When the mice go out of their holes, they can't leave behind any scent to help find their way back home (a mousy odor means dinner to foxes and other predators, who would follow the scent to mouse hiding places). So wood mice have a different strategy. They leave behind piles of leaves and twigs as signs to mark the direction they need to go.

How did scientists find out? When several laboratory mice chewed through the wall of their pen, scientists found a leaf near the escape hole. Wondering if the mice deliberately placed the leaf, the scientists set up an experiment, putting plastic disks, instead of grass and leaves, in the mouse pens. They discovered that the mice piled up the disks to mark food and other points of interest.

Using a leaf to flag a promising snack, a mouse in the wild may come back to dine at leisure. Even better, if a mouse flees from a predator in midnibble, it will know where to return. That's smart thinking: scientists thought that only humans make movable landmarks. What's next, birds with compasses?

-Jessica Tanenbaum

Copyright Carus Publishing Company Nov/Dec 2003
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