Mice use 'rodent road signs' to navigate

Mice can retrace their steps because they arrange objects to help them remember where they have been, say researchers.

Mouse intelligence is under scrutiny
These rodent "roadsigns" - piles of seed shells, leaves and other small objects - could be the first evidence of such sophisticated behaviour in any mammal apart from humans.

The phenomenon was uncovered by researchers at Oxford University, UK, who noticed that wood mice tended to move piles of small objects, then return to them frequently.

They had the theory that these were primitive landmarks, designed to help them forage for food efficiently.

To test this idea, Drs Pavel Stopka and David MacDonald brought eight wild mice into a controlled environment inside a laboratory and left them to explore it.

Disc journeys

However, left scattered around this new landscape were small white discs. A video camera recorded exactly what the mice got up to.

This is precisely how a human might tackle the problem of searching efficiently

Dr Pavel Stopka, University of Oxford
The mice seemed to meander at random around the immediate area of their nesting box.

However, further away from the box, the mice carried out more thorough "exploratory" journeys.

In addition, the mice tended to collect white discs, then move them to the more interesting areas.

The mice would then explore the area in the vicinity of the disc, continually returning to the disc - perhaps using it to orient themselves.

In the journal BMC Ecology, Dr Pavel Stopka wrote: "This is precisely how a human might tackle the problem of searching efficiently in a homogenous environment - for example placing a cane in the ground as a reference point from which to search for a set of keys lost on a lawn."

Avoiding predators

Once the mice had exhausted their exploration of one area, the researchers found, they tended to pick up the white disc, move it somewhere else and start the process again.

When a simulated threat from a "predator" was introduced, the mice used the discs to re-establish their search afterwards.

The researchers have the theory that the roadsigns might be used in the place of scent markings - perhaps as a way to cut the risk of scents being picked up by predators.

Dr Nicola Clayton, a reader in comparative cognition at the University of Cambridge, said that this was certainly a possible explanation.

She told BBC News Online: "I like the idea that mice are leaving these little landmarks to help them.

"I'd like to see further studies to find out whether this is actually having an impact on the number of rodents lost to predators." http://news.bbc.co.uk/1/hi/sci/tech/2986235.stm