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Roadsigns for Rodents: Creation of signposts detected in the first non-human species

April 28, 2003

Humans are not alone in creating 'signposts' to help them find
their way, according to new research published in the open access
journal BMC Ecology. Wood mice, say scientists, move objects from
their environment around using them as portable signposts whilst
they explore.

The finding is significant as this is the first time such
sophisticated behaviour has been identified in any mammal except
humans. According to the authors,

"This is precisely how a human might tackle the problem of
searching efficiently in a homogeneous environment - for example
by placing a cane in the ground as a reference point from which
to search for a set of keys dropped on a lawn."

Quick, effective navigation is vital for the wood mouse.
Home-ranges are vast in comparison to the mammal's size and
consist of uniform areas, like ploughed fields, without obvious
landmarks. These environments are not the same all year round,
and harvest time drastically changes the availability of any
'fixed' landmarks, food supplies and hiding places.

During field observations, Pavel Stopka and David Macdonald from
the Department of Zoology at the University of Oxford noticed
that wood mice move piles of seed shells, leaves and other small
objects as they explore. They observed that the mice are most
active around these piles and frequently return to them.

Stopka and Macdonald brought wild mice into a controlled
environment to see if they were using these items as 'portable
signposts'. Ten groups of 4 male and 4 female mice were put into
special arenas with a nest box, food supply and bedding, and
given 10, 5cm diameter white discs.

Mice were videoed constantly for 15 days, and their movements
analysed. Activity around the nest box tended to consist only of
short, local meanderings not based upon the location of the nest.
Movement around the discs, however, involved longer journeys
associated with exploratory behaviour. This behaviour was
observed in both males and females.

When a mouse found an area it was interested in, it would collect
a white disc and move it there. The mouse would then continue to
explore, its movements focused on the disc's location. Stopka and
Macdonald observed that the mice would continually return to or
'look for' the disc - apparently using it to orient themselves.
Once the mouse had finished searching a particular area and
identified a new point of interest, it would pick up the disc,
move it to the new area and repeat the exploration, again using
the disc for orientation.

The discs also served as 'book marks' for when activity was
interrupted. If a predator were detected, the mice would retreat
to shelter. Once the threat was over, the mice returned to the
disc.

Stopka and Macdonald hypothesise that these signposts are more
effective for wood mice than scent marks: they can be moved at
any time and are not detectable by predators.

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For further information please contact Grace Baynes
(press@biomedcentral.com or Tel: +44 20 7631 2988).

This article in freely available in the open access, peer
reviewed journal, BMC Ecology
http://www.biomedcentral.com/content/pdf/1472-6785-3-3.pdf

BioMed Central Limited