Pest management projects at Glenfern
Sanctuary, Motu Kaikoura, Windy Hill Rosalie Bay, Katherine Bay, Mohunga
Peninsula, the Flat Islands, and Okiwi School are all working to keep
rats at zero or low levels so that native species have a better
opportunity to survive. Each project uses different methods and all have
the goal of finding the most efficient, cost effective, and socially
acceptable way of eliminating or minimising the impact of rats on native
flora and fauna.
Glenfern Sanctuary continues to battle
with kiore reinvading and colonising within the 230 hectare pest-proof
fenced area. Interesting dynamics between ship rats and kiore are being
observed with kiore responding more quickly to the opportunity to
reinvade and re-establish in this habitat. Rabbits have also managed to
reinvade but have been contained by gassing their burrows. A new pest-
proof fence has been added inside the Sanctuary in an effort to prevent
rats coming across from Fitzroy. Rat numbers within the Sanctuary are
still low compared to unmanaged areas however, so despite reinvasion
biodiversity gains are still being made.
Bird counts taken in October have shown a
dramatic increase in many of the native species over the last counts
done in 2006. Additionally four new black petrel burrows all with chicks
in the nests have been located.
The Motu Kaikoura Trust has not been able
to sustain its eradication of two years ago. The Island is suffering
from significant rat reinvasion and long- term management will be needed
to maintain the benefits of reduced pests. Over 600 trap and bait
stations are deployed on the island and on the ‘mainland’ property
closest to the island. Rat tracking tunnels stood at 17% density in
DNA sampling of rats has not clearly
indicated whether some of the rats present are survivors of the
eradication process or if all are re-invaders. However, one ship rat
sampled was clearly identified as having come from the Flat Islands so
those pesky ship rats are still travelling by boat!
Since the Flat Island (Rangiahua) rat eradication two
years ago there have been two reinvasions that have been quickly
detected by trap catches or residents seeing evidence of rats. These
have been responded to and the invaders dealt with by the Biosecurity
team at Auckland Council (formerly the ARC), the residents, and local
business EnviroKiwi. There are 100 stations with traps, bait, and
tracking tunnels spread between the four islands and these are checked
regularly to detect any further reinvasion.
These three projects illustrate the
difficulty in achieving their goals of eradication when rats are within
swimming distance and boats are travelling short distances between areas
with and without rats.
Okiwi School tamariki are kaitiaki for its
grounds, adjoining bush and wetlands with the goal of managing pests at
low levels. This is important work as the area supports a number of
native species including the kakariki and pateke. Tamariki operate
tracking tunnels and collect data to calculate rat density, and evidence
of indicator species such as weta and lizards. The tamariki gain a
greater understanding of the impact of rats and the resulting benefits
of controlling their numbers.
Mohunga Peninsula Restoration Trust
maintains a virtual fence consisting of a buffer zone of bait stations
across the base of the peninsular. These stations also control rat
densities in areas of native bush, which are of course important food
sources for a wide range of fauna. The Abercrombie shore line is also
controlled recognising the considerable rodent activity over tidal
areas. Residents are steadily extending the areas of predator control so
that now a major percentage of the peninsular is covered. This year we
are looking forward to the results of lizard and seabird surveys.
The Katherine Bay Restoration Trust has
been established in the Bay area with local Peter Hoey coordinating the
establishment and management of 40 trap and bait stations along trapping
routes. Pre-management tracking tunnels stood at 100% in Dec. 2009.
Cages are used to trap feral cats and a local hunter keeps pig numbers
Black rat snapped. Photo: Peter Hoey
The 620 hectare Sanctuary in the Windy
Hill Rosalie Bay Catchment now has 4800 trap and bait stations and seven
either part or full-time employees. Both plant and animal pests are
targeted with a recent focus on reducing rabbit numbers. Using a
professional contractor 32 rabbits were shot and 8 burrows gassed in
February. The rat tracking tunnel results for January from the four
project areas within the sanctuary varied from 0 to 20%. Following the
significant discovery of an adult Duvaucels gecko in a rat trap in
January a comprehensive monitoring programme is now underway with the
hopes of finding a live speciman of this highly secretive gecko.
Monitoring is also underway for short and long tailed bats using
specialized equipment on loan from DoC. The North Island robins in the
catchment had a moderately successful breeding season with 13 young
fledged with four of these remaining in the Sanctuary area.