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Rodent Road Signs

Rodent Road Signs Photo Credit: Clipart.com

Experienced hikers know how to use a trail map and compass to find their way around in the woods. But what do you do if you're a tiny mouse, exploring a huge field or farm? In this Science Update, you'll hear how one species keeps from getting lost.


Transcript

Do rodents use road signs? I'm Bob Hirshon and this is Science Update.

Travelers rely on street signs to help them find their way in unfamiliar territory. Now, researchers have found that the lowly wood mouse uses a similar strategy to find its way around.

David MacDonald is Director of the Wildlife Conservation Research Unit at the University of Oxford in England. He and his colleagues have been tracking wood mice to study the effect of modern farming on wild animals.

MacDonald:

As we tracked them around using radio collars, we noticed that quite often when we were following a wood mouse, we had the impression that, rather in a puzzling way, we were finding little bits of leaf or twig that looked as if the mice had been moving around.

So to see exactly what the mice were doing, the researchers put a group of them in an enclosure containing a few small white plastic disks.

MacDonald:

They would pick up a disk, put it down when they found somewhere interesting. And then they would repeatedly return to that disk until they became bored with that particular place. And as soon as they found somewhere else interesting, they would dash back and get the disk, and carry it out to the new place, and put it down there.

The researchers think mice use such mobile reference points in combination with scent marks, to help them find their way in the big world around them. For the American Association for the Advancement of Science, I'm Bob Hirshon.


Making Sense of the Research

Suppose you were walking out of your house and dropped your car keys in the grass. The grass is deep, and you're having trouble finding them. Next thing you know the phone rings in the house and you rush to answer it. But before you go, you leave something else in the grass—maybe a book or a bag—so that you can remember exactly where you were looking.

That's just what these mice are doing, according to MacDonald's observations. Wood mice can travel hundreds of yards from their dens every night—pretty far for such a tiny animal—all in search of tiny seeds or other buried treasures that aren't exactly advertised with billboards and neon signs.

So suppose a mouse is foraging and he's just found a prime piece of dirt, when he senses the footsteps of a local farmer's cat? The mouse has got to run, but he's also got to find food, and he doesn't want to start from scratch after the cat leaves. So he grabs the nearest leaf or piece of bark, drops it right where he was looking, and runs for cover. Later on, he comes back to the same place and picks up where he left off.

In other words, these markers function not only as signposts but also as a kind of spatial bookmark. MacDonald and his colleagues determined this not just by casually watching the animals, but with detailed observations that analyzed everything from the angles of the mice's movements and the distance the markers were carried.

It's also worth noting that the researchers discovered this behavior while doing research that had nothing to do with navigation. They were just studying the movements of mice to see how farming impacted the wildlife in a particular area. They ended up discovering just one more reason why humans are not so unique after all.

Now try and answer these questions:

  1. When a wood mouse leaves a small object somewhere, what is it doing?
  2. Why did the researchers experiment by giving the mice plastic disks?
  3. What are some other possible explanations for this behavior? What kind of experiment would you design to test this explanation?
  4. Did MacDonald's discovery surprise you?What larger ideas about the way animals think and behave might it support or challenge?

For Educators

The authors' original paper appears in the online journal BioMed Central Ecology.

Animals Vs. People: Who's the Better Navigator? is a lesson from National Geographic Xpeditions that asks students to compare the innate navigational skills of humans and animals.


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