HUMAN FOOTPRINTSAchievement Standard 90811

The Rotoiti Nature Recovery Project (RNRP) was established within the Nelson Lakes National Park at the northern end of the Southern Alps in 1997. The recovery project is taken place in what has been called the mainland island. This island has natural boundaries including the Travers River, the ridgeline between the Wairau River and the lake, the edge of the lake itself and also the farm land (see photo above.) which makes it difficult for pests to swim across the lake or climb over mountains to get to the forest. The Rotoiti Nature Recovery Project is restoring honeydew beech forest by Lake Rotoiti through carrying out intensive pest control to enable recovery of native species. It was launched in 1997 over an initial 825 hectares and expanded in 2002 to 5000 hectares. Over 100,000 people visit Lake Rotoiti every year and with the recovery area right beside the campground they need only walk a short distance to experience flourishing native forest and birdlife. At the national park the land is not only home to many native flora and fauna by wild life it is an important destination for visitors to the region. Neslon Lakes National Park is over 100,000 hectares and offers a huge variety of recreational activities. There are several lakes, the largest of them being Rotoiti and Rotoroa, which have one of the countries

most valuable trout fisheries, and attract hundreds of visitors each year to some of the luxury lodges that can be found in the region. Other activities include tramping, with an extensive network of huts and tracks throughout the area, including the Lakehead track on the east side and the Lakeside track on the west side. There is a water taxi service that travels the length of the lake ferrying trampers to and from the Coldwater and Lakehead huts at the head of the lake. Rotoiti is also a popular place for water-skiing, mountain biking, skiing and boating. Having this national park where it is, does have some economic benefits, these benefits include tourists travelling to and from the Lake and passing through surrounding communities. This national park is protected by the government for the enjoyment of the general public and the preservation of wildlife. "Commercial exploitation of natural resources in a national park is illegal."

A major feature of the National Parks ecosystem is the Beech Forest, with all of the NZ Beech varieties found inside the parks boundaries. Honeydew beech forests can support large numbers of native birds, the honeydew scale insect provides an energy source for nectar-feeding birds, and the scattered and intense beech seed production ("masting") provides food for large numbers of seed-eating birds. Unfortunately this unique ecosystem has been changed dramatically by introduced animals including deer, possums, cats, rats, mice, stoats, and wasps. The goal is to reduce the numbers of these pests so that the ecological processes of this honeydew beech forest can recover. “Long dry summers with the right difference in temperature over the right time triggers a beech mast.” Said Petr Carter- Department of Conservation at Lake Rotoiti. Mast events are intensive flowering bursts among forest trees, like beech, over spring and summer. This flowering leads to a rich seed fall in the following autumn and the widely available seed on the forest floor drives a rapid increase in rat and stoat numbers. Populations targeted for additional protection include two types of kiwi (great spotted kiwi and Haast tokoeka), yellowhead/mohua, kaka, long and short tailed bats/pekapeka and powelliphanta land snails. Lake Rotoiti is a treatment site and is used to measure and show their progress, and differences between pest control site (Rotoiti) and a site left to control itself (Rotoroa). The Rotoiti Nature Recovery Project focuses on 4 pests: stoats, wasps, possums and rats. They have the most impact on the biodiversity of the beech forest. They all have different impacts on the beech forest and came here for different reasons.

WASPS

Both German and Common wasps accidentally caught a boat ride to New Zealand with some aircraft parts. German wasps arrived in 1945 while Common wasps arrived more recently, in the late 1970s, and have quickly taken over as the dominant introduced wasp species. Both these introduced wasps prey on native insects and also collect honeydew and other pollens all through the warmer months when they are nesting. There is no seasonal change for honeydew; it is made all year round. Honeydew has helped wasps build up there population, (breeding quicker). This honeydew is produced by a scale insect living in the bark of certain species of beech tree and is like rocket fuel for insects, birds and reptiles (there main food source). These wasps are a competitor for the same food needed by our native birds (bellbird, tui) and insects, and are also a meat eating predator.

In addition to annoying us, wasps have a huge impact on the honeydew found in beech forests. The presence of honeydew allows them to reach huge population numbers in the forest in the summer, up to 10,000 workers per hectare. Not only do they steal the honeydew, robbing native bird’s insects and lizards of a vital food source but they also consume vast numbers or native insects and have been recorded killing native birds. They are using methods to control the amount of wasps at Lake Rotoiti. The goals for the RNRP is; to reduce the removal of valuable food sources for native animals from our forests by wasps; reduce predation by wasps on native invertebrates and bird nestlings so that the

impacts of wasps are insignificant alongside other mortality factors affecting these groups; and improve the public’s experience when visiting public conservation land.

In the later months of summer wasps change their diet from honeydew to protein. They search and kill native incest’s to take back to the nests to feed the developing wasp larvae. Wasps are currently controlled by using an insecticide, which is mixed into a protein based, either chicken or fish. It is dyed green/blue and placed in a bait station to discourage birds (see picture above). The volunteers assist the Rotoiti Nature Recovery Project with their wasp bait trials. The worker wasps collect bait and take it back to the nest, feeding it to the queen and developing larvae, killing the nest. The bait it laid in summer when the wasp numbers reach a point called the “ecological damage threshold.” This is the point at which wasps start having a severe impact on the health of the forest. These bait stations are specifically designed for wasps and to keep nosy native birds away. This control method showed a decline of wasp nest activity (see graph below). A positive consequence of this type of pest control is that there has been a decrease in the number of wasps at Lake Rotoiti in the past 3 years; see the graph for evidence, also this impacts positively on the amount of honeydew available for our bellbirds to feed on and therefore there has been an increase in native birds at Lake Rotoiti.

Lake Rotoiti has a reputation for a lot of wasps and sand flies which put some people off coming to Lake Rotoiti, also there are a number of people that would be allergic to wasps so they will not visit the lake. Less people visiting the lake, therefore less tourism and less money for surrounding communities. A positive consequence of wasp control is that due to numbers dropping there will be less competition for food for native species including bellbirds.

Brushtail possum (Trichosurus vulpecula)

Possums are an introduced pest. First introduced from Australia for the fur trade in 1858, possums are now widespread in New Zealand, with an estimated national population of 70 million. They are omnivorous, eating bird eggs, chicks and insects as well as a wide range of forest plants. In the beech forests of Rotoiti they are known to browse native mistletoe, broadleaf (Grisellenia spp.) and fuschia, and prey on kaka eggs and chicks. Possums ignore old leaves and select the best new growth. In some areas they have eaten whole canopies of rata, totara, titoki, kowhai and kohekohe. Possums compete with native birds for habitat and for food such as insects and berries. They also disturb nesting birds, eat their eggs and chicks and may impact on native land snails.

Possums are a problem at Lake Rotoiti as they are a competitor for food for our native birds. Our native birds eat berries from the mistletoe plant. Mistletoe is hemi-parasitic plants that grow on beech, and for which there is an interesting relationship with nectar feeding birds. Bellbirds had developed a technique to twist the unopened flower buds to collect the nectar, and in doing so fertilised the flower. Mistletoe is a favourite food of possums. With most mistletoe browsed-out, bellbirds were deprived of a valuable nectar source, and the mistletoe an option for seeding. When some plants did recover, the birds had lost the ability to open the buds. Mistletoe is a very slow growing plant so once the possums have eaten it all it will take a longer time for the mistletoe to grow back. This means that the possums will have to find a different food source including many of New Zealand native birds, and insects including Bellbirds.

Possums eat everything they can find. They don’t like beech trees. They eat birds, eggs and chicks, reptiles, insects, and different sorts of vegetation that is palatable to them berries flowers seeds and leaves. Possums were identified early on in the project as something they needed to control. In the early days they used bait stations that had 1080 and prefedaton, this worked really well and the possum numbers dropped using this technique. Since 2000 they have been using single action kill traps, these traps are aimed to kill and hold one animal at any time, they have to be manually reset. To monitor the possums they look at what the mistletoe trees are doing, every year they do a foliar browsing on each of their mistletoe that are tagged so that they can compare that year to year. Another technique they use is manual chew tags, they are put on the trunk of a tree and possums

come along and chew on what they think is food but is actually a waxy nob on the end of the tag, they use sugar or flour in the wax nob to attract the possums. This gives them an idea on possum numbers as nothing else can climb trees and do damage to a wax nob apart from possums. They do this every 2 years for 7 nights and they need a clear dry weather window. The future goal for possum control is to stop them reinvading from the south end of the mainland island. This year so far: 400 possums have been caught. Possum control is moved around as the population moves. See map below for trapping results. Possums are also being tracked by tracking tunnels. They don’t kill the pest; tracking tunnels are only used to keep track of numbers/ tracking rate. 1 card with print counts as 1. Docs goal is 5% or less so 5 out of each hundred cards to have a print on them. They don’t have goal of 0% because the mainland island has no predator proof boundaries or fences (no physical barrier) they would never be able to have 0% because of re invasion. 5% is the rate at which the birds can still breed successfully and produce offspring and have a healthy vibrant population. Two years ago AHB reduced their possum control in Big Bush and this may result in possum numbers gradually increasing in this key kaka breeding area The level of possum browse observed was very low and overall health had improved in all species since the last survey in 2008, with many plants having increased in size and foliage density. This indicates that the current level of control within the RNRP is successfully keeping possum numbers low. Some consequences of DOCs work with possum control is that there has been a decrease in population numbers therefore there is a small increase is native birds e.g. bellbirds. Also less

competition for food and more mistletoe available. A negative consequence to possum control is that there will be an increase in rat and mice numbers as they are a food source to possums. A cultural impact of pest control is that if its successful then there will be an expansion to the mainland island. A social impact is that if pest control is successful then more people will want to come and visit Lake Rotoiti therefore will pass though surrounding communities which is and economic impact.

Stoats

Stoats, ferrets and weasels, collectively known as mustelids, were introduced in the late 1800s, in an unsuccessful attempt to control rabbits, which had built to pest numbers on grazing land. Ferrets are generally found in the open country where as stoats (and in lower numbers weasels) are found in bushed areas. Stoats are agile climbers and aggressive killers, and are extremely damaging to the local wildlife. While they eat rats, they also feed on eggs and chicks of many birds, including kaka. Stoat and rat numbers fluctuate in response to beech tree seed fall. The Department of Conservation (DOC) are expecting at the end of the winter when the seeds have germinated the rats and stoats will turn to native birds when it’s time for birds to nest. In order to work out the relative abundance of rodents and mustelids they use tracking tunnels.

The tunnels have a foam pad in the middle soaked with ferric nitrate. The papers at each end are treated with tannic acid. The ferric nitrate collected on the animals foot reacts with the tannic acid on the paper leaving a paw print. This method even works even when the animal is wet. The tunnels are left out over 4 nights. The first night are baited with peanut butter to attract rats through the tunnels, the following 3 nights with meat to attract stoats. The percentage of tunnels tracked gives DOC a tracking index. DOC is aiming to achieve an index of 10 percent or lower with the trapping programme. Above 10 percent, rodents and mustilids start to impact seriously on the breeding success of native birds. Tracking tunnels are also used at non treatment sites (Rotoroa) to compare results with what is happening in areas in where pests are not controlled.

At the Rotoiti Nature Recovery Project, stoats are controlled by trapping. The traps are baited with a white hens egg and set in wooden tunnels. These tunnels are designed to do two things. Firstly they reduce the risk of accidently catching a non-target species such as wekas. Secondly, the way the trap is set in the tunnel ensures that the stoat is caught quickly and humanly. Stoat control lines are located are laid alongside landscape features; like the lake edge, the range tops and prominent ridges. A trap in a tunnel is placed every 100m along the lines. Lines are checked more often in summer as the stoat numbers are at its highest and native birds like weka and kiwi are nesting. The frequency in checking the traps are then decreased to once a month as the season changes to winter as the stoat numbers have decreased and the vulnerable native birds are not nesting. Stoats enter the box through a small 5cm hole in the mesh end, then through another entrance to the trap compartment where they have to travel across a trigger plate to get the bait.

South Island kaka is a large parrot which rest in holes in mature trees. The female kaka incubates the eggs and feeds the chicks with food brought to the nest by the male. Stoats are one of the main threats

Stoats are a threat to the unique ecosystem of Lake Rotoiti

to kaka, particularly to eggs, chicks and nesting females. Females incubating eggs and chicks are killed every year by a stoat, which is causing a serious gender in balance in the population. Most of the kaka you see in the wild will be male.

Mice, rats and stoats predate heavily within the forest; plant growth is slowed and bird numbers are reduced. In mast years the huge food source can cause stoats to reproduce more and stoat number vastly increase. Stoats eat the rats, if there is a higher rat numbers then that could account for higher stoat numbers. Doc is doing well compared to their non-control site, but isn’t reaching their goal of 5%.

By just doing stoat control it means rat and mice numbers will explode because of predation, thus being harmful to many of the native animals, in particular birds. You can’t just control one thing, have to keep it balanced. If doc carry on doing pest control at Lake Rotoiti for many years to come there will be a big increase in tourism as the wildlife will flourish and it will become a must see while in the nelson area

Due to the development of the mainland island in the Nelson lakes national park, an area of native bush has had special management processes put in place to look at future sustainability issues. Sustainability is the management of our natural resources so they are around for future generations. The sustainability of the mainland island is very dependent on the ongoing success of pest control in the area, if pest control is consistent then all our native bush and animals will be around or future generations. Another thing that impacts on whether the park will be sustainable is the funding from the government, if the funding goes down at any stage then the park will not be able to be maintained and therefore will not be sustainable. Personally i think that the work done by the FOR and the DOC staff has had a huge positive impact on the ecosystem at Lake Rotoiti and i hope for its future success.

Ship Rat Control

Ship Rats are an introduced pest, arriving on ships accidentally. Most native bush birds are susceptible to predation by rats as they are known to be excellent tree climbers using their long tails as a “fifth limb”. They have a huge impact on wildlife as they prey on birds and chicks and eat their eggs which consequently results in less productivity/reproduction. As well as being a predator to Native birds, in particular the south island Robin rats also feed on native fruits and seeds, in particular beech seeds at Rotoiti and are therefore competition for our Native species for food. Rats are also difficult to control as they can reproduce up to 10 offspring in a period of 8 weeks if there is an abundant food source. This also means that they can easily reinvade controlled areas making it labour intensive to control them.

Rat control has proven difficult over the years within the Mainland Island. In the years between 2000 and 2007 snap trapping was trialled as a way to control the rat population. This involved bait to lure the rats into the trap and snapping down and breaking their backs. This was repeatedly unsuccessful as it proved labour intensive and was not sustaining a less than 5% tracking rate and so consequently was stopped.

As a result of snap trappings failure it was brainstormed between the years of 2007-2010 about the best way to control the ship rat population. It was not cost effective or affordable to control them with poison and bait stations year round. It was also unsafe as it raised concerns for the safety of the short tailed bats. 2010 saw to a concentration around control within the Mainland Island with a preferred outcome of passerine productivity increasing as opposed to primarily focusing on protection. It was noted that the most predation on birds occurring during the nesting season and concerns were also raised that a year round control could lead to bait shyness and immunity. Consequently it was decided that they would sporadically control rats throughout the year, primarily in spring while birds are nesting and this was successful in increasing Passerine levels throughout the core of the Mainland Island.

Throughout 2011-2012 two control methods were carried out within the Mainland Island. The first occurred in Spring 2011to reduce the Ship Rat numbers before the South Island Robins breeding season and the second occurred in April 2012 in the anticipation of a partial beech mast. Diphacinone, commonly known as Ratabate in paper bags were placed in bait stations and the amount was dependant on the density in the area the traps were placed. The bait was placed over a period of 3-4 days and stations with bait remaining after 6 weeks were removed. The September operation was successful and met the <5% target however the April one was less successful as a believed result of their being an abundance of natural food. This was proven as Tunnels recorded rats with no peanut butter intake which further suggests ample natural food source.

The rat control grid now covers 867ha throughout the Mainland Island which is close to the effective 1000ha ground based rat control minimum.

Tracking Tunnels are used to collect data and provide an indication/monitoring system as to the quantities of rodents in an area, in this specific instance the abundance of ship rats. Rat tracking supported the 2011 Spring operation as it found a decrease of 6% in the amount of rats tracked in the core area compared to Big Bush and at Lakehead.

The rat control operation in September also had consequences on the success of the South Island Robin's breeding season. When only trapping of rodents/rats was conducted it proved a dramatic decline in the population of the Robin however the amount of Robin pairs increased when Ratabate poisoning was carried out. Before the September operation six robins (4 male and 2 female) were spotted within the focus area. However, after the operation between 9-15 chicks fledged successfully.

The increase in the amount of successful offspring within the Robin population is a direct consequence as a result of the September operation. By monitoring the Robin count the Rotoiti team are also therefore able to measure their success within their experiments as an increase will prove success and a decrease will prove unsuccessful and consequently they will have to change their control methods.

This graph shows the number of Robins and Robin pairs within the RNRP core area during each Rat control operation. It clearly shows that during 2011 and the September operation that the amount of robin pairs found in the reserve had increased rapidly.

LINKS

http://www.doc.govt.nz/conservation/restoration-projects/mainland-islands/rotoiti

http://www.doc.govt.nz/conservation/restoration-projects/battle-for-our-birds-beech-mast-2014/

http://www.doc.govt.nz/Documents/conservation/land-and-freshwater/land/rnrp-annual-report/rnrp-annual-report-2010-11.pdf

http://www.doc.govt.nz/conservation/restoration-projects/mainland-islands/rotoiti/docs-work/rotoiti-nature-recovery-project-restoration/ecosystems-and-impacts/

http://www.doc.govt.nz/conservation/restoration-projects/mainland-islands/rotoiti/

http://www.doc.govt.nz/Documents/conservation/land-and-freshwater/land/rnrp-annual-report/rotoiti-annual-report-2011-12.pdf

Also Petr Carter