Page Sec1:44 - Labyrint 2013 - English Edition

The world’s northernmost bat colonies
are found surprisingly far north. At 69
degrees north, in the interior valleys of
Troms County in Norway, small groups
of northern bats battle to survive in the
inhospitable and unsuitable climate.
“Normally, active bats require minimum
air temperatures of about ten degrees C.
In Troms, temperatures may creep down
to zero on cool autumn nights,” says
Karl Frafjord, a zoologist at the Tromsø
Museum.
Frafjord has spent years studying bat
colonies in Troms, including how these
nocturnal animals tackle the challenges
of the midnight sun and the long, bright
summer nights in the north.
Normally bats would never venture out
until after sunset.
“There are several theories about why
bats evolved to be nocturnal, but most
agree that it is most probably to avoid
being eaten by birds of prey in the
daytime. So bats in the north have a
difficult dilemma. They can either brave
the bright summer night risking life and
limb, or they can starve to death while
they are waiting for darker nights,”
Frafjord says.
Hidden by the dusk
After their long winter hibernation, bats
have no other choice but to risk their
lives to fatten themselves up. This is
especially true for pregnant females.
Frafjord explains that even though the
sun does not set, the bats in Troms can
take advantage of the low light condi-
tions during the summer’s very short
twilights, when the midnight sun dips
down behind the area’s surrounding
mountains.
“We’re not talking about a long time
each night, but luckily they can catch
their night's ration of a few thousand
Bright summer nights and freezing winters,
are a constant threat to north Norwegian bats.
Creatures
of the Night
44 ••• Labyrint E/13 – University of Tromsø