research in wetlands and grassland areas with GPS
big issue nowadays in Holland is the rather recent intrusion of foxes into
meadow bird areas. The large and dense populations of meadow birds (especially
godwit Limosa limosa, lapwing Vanellus vanellus and redshank Tringa totanus)
in our agricultural regions are regarded as a national responsibility. The
last decades however the meadow birds have been decreasing in numbers, mainly
because of the ever increasing intensification of agricultural practices. In
the same period the main meadow bird regions have been (re)colonized by
buzzard, goshawk and red fox. Many people put the blame of the meadow bird
decrease primarily on the red fox, being the only species which can legally
be killed. A recent large study into the extent and actors of predation in
meadow bird populations (Teunissen et al., 2005) has shown that a large
number of predators is responsible for the loss of clutches, and a largely
other group of predators for the loss of chicks. Where foxes occurred, they
sometimes had a large part in the predation of eggs, but sometimes they had
not. Although a general large influence of foxes on meadow bird populations
could not be found, in some areas a need is felt to control foxes.
of 'Yolanda' with the GPS-collar,
just before release. Photo by Nico Dekker.
develop tools for the authorities to make sound decisions on fox control in
meadow bird areas, in 2007 a research project has started into the ecology of
foxes living in this 'new' habitat: wet grasslands interspersed with numerous
ditches. To begin with, a female fox born in 2006 has been caught in July and
fitted with a GPS-transmitter, as far as I know the first fox carrying such a
tracking device. She ('Yolanda') lives in a wetland, consisting of meadows
and reed lands separated by narrow and broad waterways. Not a single tree
grows in her present home range and there are no opportunities to dig a den.
The fixes (location data) are stored on board of the GPS-module and can be
recovered by a blue tooth connection at specific pre-programmed dates and
times. A regular transmitter is also included in the collar, enabling the
necessary approach (by boat!) to within 50 to 100 meters to recover the data.
The first GPS-device took its position every 12 minutes during the dark hours
on even nights, and every hour on uneven nights. This way the battery of the
GPS-module lasted 2.5 month, during which period almost 2400 fixes were
the data with a
blue tooth antenna on a laptop
In December 2007 she was caught again, by chasing her into standing nets, to
change her collar. The new GPS-module takes its position every 6 minutes
during the night, producing a very detailed picture of the path the fox has
walked. Potentially we now are able to link her activities with locations
where bird nests have been robbed, etcetera. An example of one nightly stroll
is shown here; the black lines form a 1 km grid.
The collars are made by two Dutch technicians. Contact me for details.
of Yolanda during the night of 27-28 December 2007.
Fixes taken every 6 minutes. Black lines form a