With this wetter warm autumn on Barrier
there has been huge food abundance in our bush which is good news for
birds, lizards, and insects, but its also great for rats. The well
documented bulge of autumn rats which has usually started to trail off
by now remains high.
In the Windy Hill Rosalie Bay Catchment
Trust sanctuary, however, we have had our lowest ever autumn results
since we began using tracking tunnels to monitor for the presence of
rats in 2004. This has been achieved with a single perimeter track using
Pest-Off (Brodifacoum) and traps at 12.5 metre spacing, with our
interior tracks using Rat-Abate in stations set 25m apart.
A key to the success of this mixed
programme has been the input of our keen volunteers Brandan Kerr and
Dave Harland. Brandon has checked bait and trap stations on the
perimeter tracks weekly – which takes fourteen hours – and this has
assisted to keep the rate of rat re-invasion into the sanctuary area
down. Dave manages part of the Benthorn Farm project area and is also
able to check traps on a weekly basis ensuring that they are continuing
to catch well.
It seems that a mix of management tools
with a high level of station checks has done the trick this autumn.
The current goal of the Trust is to find
the most effective, cost-effective, and socially acceptable way of
keeping pests at very low densities. It takes time to find this out as
each method needs at least two years of operation before the efficacy
can be assessed and seasonal variations and climatic events allowed for.
So far at Windy Hill we have trialled 6
years of trapping, 4 years of traps with short pulses of rat bait (Feracol-cholecalciferol),
18 months of Pest-Off (brodifacoum) bait, and a year of the less potent
Rat-Abate (diphacenone) which is put out and replaced three times a
Trapping only has proven to be the least
effective with a minimum of 30% and a maximum of 73% tracking tunnel
percentages recorded. This has proven that toxins are required as part
of any on-going pest management if we are to keep the rat and mice
numbers low enough for the biodiversity to be sustained or improved. The
Trust is working towards finding the least amount of toxin that can be
used that combined with other methods still achieves a good result. We
are close to finding that out – the Sanctuary rat tracking tunnel
average for 2010 was 9% and the Control, or unmanaged area, stood at
76%. That represents a lot of rats that are not eating our precious
native species in the Sanctuary.
Autumn (April) tracking tunnel
percentages for Windy Hill and the unmanaged Control Site: