The results of the trapping trial
designed to help inform plans to remove stoats from Orkney in order to protect
Orkney’s internationally important wildlife have been revealed.
The Orkney Native Wildlife Project carried
out the trial as part of the nine month development phase that was funded by
the Heritage Lottery Fund as part of the work to optimise technical aspects of
the planned eradication. This will be the world’s largest stoat eradication to
date and a first for Europe, so it was important to test some elements of the
methodology to ensure it will be successful and to investigate differences in
stoat behaviour in Orkney.
In December 2017, lethal humane
traps were positioned at three trial sites west of Kirkwall – Grimbister,
Hobbister and Wideford. In order to determine their effectiveness, a range of
trap types and trap housings and a range of habitats were tested. The traps
were then checked eight times between mid-December and the end of February with
number, gender and trap location of each stoat caught being recorded.
A total of 41 stoats were caught
across the three sites with nearly half (49%) of these caught at the Grimbister
site. Overall, eighty-five percent of stoats caught were captured in the double
set traps (where there were two traps in each box with an entrance at both
ends). Trap were set in improved grassland, rough grassland and moorland, with
the vast majority of stoats caught in moorland followed by on the edges of
moorland and the coast.
The main finding was that the
density of stoats in these three trial areas appears to be high compared to
other islands around the world where stoat densities have been estimated during
eradications. The estimated density of stoats in the three Orkney areas was 2-4
per km2 compared to the total density of stoats from Secretary Island and
Resolution Island in New Zealand of 1.1-1.4 per km2 and 0.7 per km2,
respectively. This difference in density is likely to be an underestimate too
as the calculated density of stoats caught would be considerably higher over
many years of trapping (like that which took place on the New Zealand Islands)
compared to the 12 week trapping trial in Orkney. This is the first time that
an indication of the abundance of stoats in Orkney has been available.
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