Miramar Peninsula
Greater Wellington regional council and theWellington City Council have been working to reduce possum populations in the Town Belt and reserves since 1995. The objective being to enhance native birds and plants.
In 2002 the Miramar Peninsula was heavily infested with possums and bereft of bird life with no resident tui or woodpigeon. The peninsula was identified as a potential site for possum eradication. Wellington Airport and the sea form an excellent barrier to possums, and once possums have gone, reinvasion will be very unlikely. The Peninsula was identified as a vital link in a bird corridor from the Rimutaka Ranges to East Harbour Regional Park and across to Karori Wildlife Sanctuary
The Peninsula is 822 ha in area, 6.5k long and 2.5k wide. There are many private residential and commercial properties, as well as larger landowners eg Civil Aviation, N Z Defence Force, Miramar Golf Course, that occupy about 50% of the Peninsula.
Some large stands of native vegetation occur along the coast, exotic trees in the north and regenerating native bush in the south. Along the coast are cliffs, rocky shore platforms and gravel beaches.
Conservation values are not particularly high, presence of native bird species limited ( silver eye, fantail, grey warbler). There has been a history of possum nuisance calls to Greater Wellington regional council from residents since 1991.
Miramar - Aerial view
The possum eradication operation
After initial research into the proposal, monitoring was undertaken to get an idea of the density of possums. This was conducted by GW staff using leg hold trap, to obtain a residual trap catch. The result for the northern part of the peninsula was a high 40% and for the southern part a moderate 12%.
Note: Residual Trap Catch (RTC) is a nationally standardised possum monitoring
method using lines of leg-hold traps. The%RTC represents the percentage of traps which captured a possum. E.g. 5 possums caught from 100 trap nights would be a 5% RTC.
Bird count monitoring
A company was contracted to conduct 5 minute bird counts in Mapuia Reserve, on the Miramar Peninsula. This is a way of assessing the distribution and relative abundance of native birds present.
The numbers of each bird species (seen and heard) are recorded over a five-minute period at each of a series of marked stations located at least 200 m apart.
The counts are being continued every year, to find out if there has been any change.
Public relations
The public was generally supportive of the possum control programme. A high level of communication was maintained with residents. Individual property owners were approached and asked if bait stations could be placed on their land. If they were uncomfortable about the use of toxins, staff would discuss the reasons and offer the alternative of a kill trap, or a neighbouring property owner was approached.
Methods used
Three different poison baits and three different kinds of traps were used on the peninsula .
Where public access was limited on the large northern properties owned by Defence and Corrections Depts, the pesticide encapsulated potassium cyanide ( Feratox) was used. Brodifacoum cereal pellets ( Pestoff) and leg hold traps were used for follow up work.
Brodifacoum and cholecalciferol cereal pellets ( Campaign) were used at the southern end and on the ridges
The remainder of the peninsula was controlled using brodifacoum pellets in bait stations and kill traps.
This work began in Feb 2003, after children were back at school. Greater Wellington staff installed a total of 647 bait stations spaced at 100m intervals. Bait stations were placed on a tree or fence post, which was sprinkled with a mixture of flour, cinnamon and icing sugar to lure the possum to the bait station. Bait stations were checked regularly and refilled at least monthly until no more bait was taken.
Timms or Possum Master kill traps baited with apple, were used where a landowner was concerned about the use of poison.
Miramar - traps and bait stations; yellow circles = bait stations, red crosses = traps
The Results
A year later in Feb 2004, following 12 months of intensive possum control, no bait had been taken from any of the 647 bait stations for 2 months. A useful means of assessing possum numbers is monitoring using wax tags. These are pieces of wax with a lure, that a possum will bite. 90 tags were left for 4 nights at random points on the peninsula. The bite marks showed that only rats were present.
Several other checks for possums were made on the peninsula. All the likely possum habitats were surveyed at night using a spotlight. Possum dogs were used to check dense coastal vegetation. Pine trees were checked in the pollen season. During all these inspections no animal or fresh possum sign was seen. Some residents reported seeing possum droppings, but almost all turned out to be hedgehog droppings.
The last known possum on the Miramar Peninsula was a juvenile female trapped near the foreshore in Feb 2006, and thought to have been released.
Precautions taken to protect people and their pets
The three designated dog exercise areas on the Miramar Peninsula were trapped using kill traps placed high in trees, before bait stations were installed. This reduced the chances of possum carcases in the exercise area. Specific warning signs were installed and only brodifacoum poison was used in bait stations.
Bait stations were placed at a minimum height of 1.5m to be out of reach of dogs and children.
Information sheets were delivered to residents
Schools, kindergartens and community groups were sent letters informing them of the operation
Any residents who reported a possum carcass on or near their sections was visited and the carcass removed.
How successful?
In Jan 2004 tui were breeding on the Miramar Peninsula, the first instance of tui breeding for many decades. Both kingfisher and kereru have returned to the peninsula
What about the cost?
The costs for the Miramar Peninsula possum eradication programme were shared between Greater Wellington regional council and the Wellington City Council. Greater Wellington Biosecurity staff undertook the administration and all the control work.
Labour was the greatest cost (68%), materials (16%) vehicles (12%) and advertising (4%)
Total over 5 years = $102,190 Year 1 = $66,000
Sources: Keeping Miramar Peninsula possum free
Greater Wellington November 2005
Greater Wellington Report on the Miramar Peninsula possum eradication operation 2008
Miramar - Moa Point