10
SQUEAK___SQUEAK___SQUEAK - THIS IS RADIO MOUSE
CALLING
If you tune in to Essex Radio North, the transmitter
you are listening to is in Baker's Wood, Coptfold
Hall. Many Essex Field Club members will know this
splendid private estate, as the owners (Col. and Mrs.
Upton) are keen naturalists and have allowed us to
hold meetings on their land. It's not only Essex
Radio that broadcasts from Coptfold Hall - a few
million times less powerful and weighing only two
grammes are the transmitters that a few of the yellow-
necked mice wear as collars around their necks.
For many years I have been studying the wood mice and
yellow-necked mice by catching them in Longworth
catch-alive traps, marking the mice so I know them ind-
ividually and following their life spans and long-
term movements. Short term studies are much more
difficult - you can't go out 'mouse-watching' in the
way you can watch badgers or deer. The mouse radios
are helping to solve this problem. With a special
receiver, a hand-held aerial that looks like a roof-
top T.V. aerial, and a set of head phones, I can tune
into my radio mice from a hundred yards or more away.
The wave length tells you which mouse you are listening
to and by turning the aerial you can find out which
direction it's in. The closer you get to the mouse
the louder the radio bleeps.
It's early days yet, and I have only followed a few
mice for a few days at a time. At best the radios
work for a fortnight before the battery fails and
I have to re-catch the mouse and remove the radio.
But already the radios have revealed some secrets
about mouse activity. One male spent nearly all
his time in early February up in the tops of trees -
even staying in a tree hole by day sometimes. Others
have underground nest sites which they often change -
sometimes moving during the day, even though mice are