History of Rotoitis biodiversity

History of Rotoitis biodiversity

Before humans arrived in New Zealand the islands had been separated from other large land masses for millions of years. This meant that the flora and fauna could become highly specialised to their specific environment with a high number of species living there that could be found nowhere else in the world. The animal community was predominantly dominated by birds and insects; it had no terrestrial mammals except bats.

Rotoiti is a beech tree forest ecosystem and before the arrival of humans supported a large variety of animals. Yellow-head, kaka, kakariki, south island snipe and other bush birds in large numbers. Several different species of kiwi moved about on the forest floor along with weka, takahe and New Zealand quail. Piopio flitted through the bush and laughing owl hunted on the ground. On the lake lived several species of endemic duck and in the lake lived grayling trout. Haast's Eagles, one of the largest known birds of prey, soared through the sky searching for their main prey, the moa.

Then a new era began with the arrival of the Maori people about 900 years ago. Long isolation with few predators meant that plants and animals did not have the adaptations needed to effectively protect them when new predators and competitors were introduced. This made them especially vulnerable to the changes that the arrival of humans brought. With the arrival of the Maori came the Polynesian rat, though whether it came as a stowaway or a food source is unknown. In the cooler south island the plants the Maori brought with them to help colonise the new land did not grow. Therefore, to survive the Maori had to rely on what they could hunt and forage. The moa, large flightless birds, were hunted to extinction and Haasts eagle that deepened on them for its food supply soon followed. Rats hunted the smaller birds and ate their eggs as well as the seed many birds deepened on for a successful breading season. Several species of birds became extinct and many others suffered a severe drop in numbers.

The Rotoiti ecosystem was left reeling, but a greater disaster was yet to arrive in the form of European settlers. Within 50 years of European arrival the New Zealand quail was extinct. Larger birds such as the Laughing owl which had survived the arrival of Maori without to much of a drop in numbers could not survive the introduction of larger predators such as cats and stoats. Predation by cats and rats caused the struggling Piopio population to decline rapidly; the last confirmed specimen was shot in 1902. The introduction of rainbow and brown trout into New Zealand waters caused the realised niche of the grayling trout to shrink into nonexistence due to heightened competition. The number and biodiversity of native and endemic animals living in the Lake Rotoiti forest area began to lessen under the combined pressure of new predators and competition from things like wasps, possums, stoats, hedgehogs and rats. The birds were beginning to fall silent and the hum of the wasps was becoming almost deafening.

Then at last things started to go in favour of the native animals in the area. It was decided to take the idea of what conservationists were doing on offshore islands and apply it to create an island in the nelson lakes national park. So, in 1997 the Rotoiti Nature Recovery Project (RNRP) was established. Initially 825 hectares of easily accessible land close to the visitors centre was selected because of its honey dew beech forest being similar to the forests that once covered New Zealands south island. In 2001 the control of mustelids and rats expanded to adjacent forest bringing the area of land under conservation to around 5000ha. Also in 2001 the community conservation group the Friends of Rotoiti (FOR) was established, this has led to a larger and more effectively covered area of pest control.

Although it was too late for some species, the future of native animals and plants living at Rotoiti is looking more promising and the conservation effort has made it possible to begin reintroducing native and endemic animals into the area. The following report will discus just what is being done in the Mainland Island, how progress is monitored and how it is affecting the biodiversity of Rotoiti.

Pest Control

One of the main things that DOC and the Friends of Rotoiti are doing in the RNRP is the killing of any pests in the area. It is impossible for them to remove all the predation and competition imposed by introduced species because Rotoiti is not isolated like a true island and pests can immigrate into the area. However, they can control the numbers of pest species living in the Mainland Island.

There are several key species of pest that they aim to control with various methods, they are:

1. Wasps

The common wasp first arrived in New Zealand in the 1970s and soon spread through the country due to its relatively mild climate, abundance of food and lack of animals that could effectively act as predators towards them. Wasps pose a double threat to the native animals living at Rotoiti. During wasps summer breading season they not only out compete birds such as bellbirds, kaka and tui for the honey dew and invertabates that they need to have a substantial population, but can also kill unprotected chicks and native insects to feed their larva protein.

In 1998 the RNRP started an operation to control the wasps in the 825ha core area using protein based bait (chicken) that is mixed with the poisons Fintiron or Fipronil (also known as Xstinguish) into a paste. As Xstinguish is the more effective of the two poisons they use this whenever available. Their aim is to bring the number of wasp nest down to less than 2 nests per hectare or drop nest sizes by 85% or more. A bait station designed especially for the wasps is nailed to a tree and 40g of poisoned bait is placed into it. The bait is left out for 3 to 4 days during the stage when the wasp larvas development requires the adults to gather protein rich foods (early February). Any leftover bait is then removed and weighed to see how much the wasps have taken, monitoring how much bait is retrieved is one of the ways that DOC can monitor how effective their methods are. Wasp control methods are not employed every year. To decide whether or not to lay the poison they set test bait (bait that has no poison in it) in the traps and see how many wasps are seen visiting the bait stations over one day. If the average number of sighted wasps is over 1.5 then the following day poisoned bait is applied to the stations. Over the 22 years that DOC and FOR have been working together on the wasp control project they have noted marked a decrease in wasp numbers. Numbers of tui and bellbirds have notably increased and in May of 2000 visitor to the park Cees Bevers stated, Ive never seen so many bellbird and tui in one place and I saw it at a low bird activity time of day just after lunch. It must just be fantastic at dawn. ( )Something that many visitors do not notice is the increase in native invertebrates population size and density. This increase can occur as a result of a decrease in predation by wasps.

2. Possums

(The sentinel kill trap) (The warrior kill trap)The Brush Tailed Possum arrived in New Zealand with the European settlers who tried to establish two populations of them in order to start a fur trade. The first group arrived in 1837 and the second group in 1858. At the time the introduction was thought very successful, but now we see them as a serious threat to the biodiversity of New Zealand native and endemic species. From early on in the RNRP possums were targeted in order to minimise as much as possible the damage they were causing through their predation of native invertebrates (particularly land snails), damage they were causing to nests by consuming eggs and young chicks and prevention of native plants being able to re-establish and reproduce due to possums eating new shoots and seeds.

The type of possum traps used in the RNRP have varied over the years as more effective means of controlling possums have been found. Currently two different traps are being used to target possums; the Warrior kill trap and the Sentinel kill trap (these are baited with aniseed paste). The more effective of the two, the sentinel trap is used in the core area, when this trap was first introduced record numbers of possums were recorded as killed.

The Philproof bait station is usualy used to control rodents but the RNRP is using it to help control possums as they can reach up through the tunnel to get at the poisoned bait. The novelty of a new object is, for a possum, as much an incentive to investigate as the smell of possible food. Therefore, all the traps used for the control of possums are moved from tree to tree at regular intervals to stimulate the possums interest in it. The Philproof bait station is especially easy to move as it is fastened to the tree with only one nail. Thus understanding about possums nature has lead to more effective trapping.

(Wax tag )Careful monitoring is also an important part of controlling the possum population, as it allows members working on the RNRP to locate areas where high numbers of possums are living. This shows where their traps and efforts need to be concentrated. One way of doing this is by using wax tags. A wax tag has a lump of wax on the pointed end of a small peace of triangle shaped plastic. The wax is shaped like an egg and to a curios possum it is a very effective likeness. When the possum takes a bite it leaves teeth marks in the soft wax, but because it finds that not everything is as it seems it leaves the tag alone. After leaving the tags nailed to the trees for a set time the tags are collected in and DOC member tally how many bites are on each tag, and how many tags in an area have bite marks, this is called the Bite Mark Index (BMI). The correlated information is then used to create a plan for where the traps will be placed.

Another way to track possums as well as other larger pests is through the use of tracking tunnels.

A white card with wet ink in its centre is placed in a tunnel that is baited with non toxic bait. When an animal enters the tunnel it walks across the ink and then leaves its paw prints on the white paper. The cards are then collected and the paw prints identified and tallied. For different animals that they wish to track different baits or tunnels are used. These are often used as a base mark for success of control measures. e.g. target of 5% or less tunnels show paw prints of a species.

(Comparative size from right to left: weasel, stoat ferret )3. Mustelid (Stoats, ferrets, weasels)

Mustelids were introduced into New Zealand in the 1880s to control rabbits. Scientists warned against the consequences, but the farming community demanded the introduction. Within six years the bird population had suffered a severe drop in numbers. Mustelidae are a threat to native birds through predation, especially for ground birds whose adaptations cannot protect them from this new threat. Mustelidae also prey on rats, mice and insects. During a beech mast the beech trees produce a bumper crop of seeds, stoats dont eat seeds but rats and mice do. In response to the increase in available food the rodent population increases. This prompts the Mustelid population to increase. When the beech mast finishes the rodent population drops sharply because of higher predation and lack of food. The mustelid population, though, dose not immediately decrease, they simply change the species they are hunting from rodents to birds.

To protect the native species of birds and insects living at Rotoiti the RNRP team has found it necessary to minimise the Mustelid population as much as possible through the use of kill traps. The RNRP runs 24 trap lines with a total of 920 traps. DOC has found that the DOC200 and the DOC250 traps are proving the most humane and effective traps, killing a much wider range of species than just mustelids. Other species include rats, mice, hedgehogs (that are decimating the population of native invertebrates as well as consuming the eggs of ground nesting birds) and feral cats (another contributor to the predation of birds). To prevent native (Smaller and with a lower trigger weight this trap more effectively kills smaller animals such as rats and mice as well as its target species stoats, ferrets and weasels.)animals from being killed the trap is enclosed in a wooden box with several key futures.

(Larger and with a higher trigger weight, this trap more effectively kills lager animals such as hedgehogs and cats as well as its target species stoats, weasels and ferrets. )1, each end of the box is wire mesh so the animal can see all the way through, therefore it will think that it can easily get in and out. 2, the entrance to the box is a hole in one corner just big enough for a mammal to get in, but to small for birds such as weak to fit through. 3, the box has a second partition wall made of wire mesh with a gap on the other side of the box to the initial entrance. This gap leads straight on to the trigger plate of the trap, ensuring the trap closes on the animals head every time. Putting two gaps that create a kinked entrance to the trap prevents birds like weak sticking their head into the box and setting off the trap by accident.

All traps set on a trap line are spaced 100m apart and are bated with a chicken egg. In a normal year traps are checked every two weeks in summer lowering to every six weeks in winter due to the lower catch rate. During a beech mast traps are checked at least every week and it is common practice to borrow traps from other DOC protected areas to keep the increased number of Mustelids under control. Thanks to the FOR the RNRP can place traps outside the reserve to prevent Mustelids from entering the controlled area.

4. Rats

There are three different kinds of rat living in New Zealand, the Norway brown rat and the ship rat (or black rat), and the pacific rat that was introduced by Maori settlers. Of these three the pacific rat and the brown rat have been eliminated from the Rotoiti area.

The black rat had arrived in New Zealand before 1800 with the European settlers or possibly sooner on one of Captain Cooks exploration ships; it threatens native fauna in several ways. Firstly, it directly affects native birds through predation, eating eggs and chicks as well as any smaller birds. (Native lizards are also under threat from predation by rats.) Secondly, they offer competition for food resources eating any seed and fruit available. This is because, as there had been no mammals other than bats living in New Zealand until rats arrival with humans, birds had filled the niches traditionally held by the black rat. The adaptations possessed by rats are proving the most effective and they are now outcompeting the native birds for the resources in niches they formally filled. Because the reproductive rate of a rat is faster than the native birds any increase in available resources is exploited by the rat population before the birds can react. Therefore bird species that rely on years with increased resource availability for a successful breading season can no longer successfully reproduce. Finally, the black threatens native fauna by carrying disease. For these three reasons the RNRP has found it necessary to implement rodent control measures. The target was to get a 5% and lower tracking tunnel index sustained throughout the year. (Although there are mice at Rotoiti they do not cause as much of a problem for native fauna as rats and therefore are not being specifically targeted.)

Rat control methods at Rotoiti are not fixed to one specific method. As a leader in research into new means of controlling rats the RNRP never sticks with one control plan for long and is constantly changing and comparing methods. Methods used to control the rat population include: 1, the Philproof rodent bait station. The RNRP spent several years testing the effectiveness of this control option. The poison bait used in these stations is 1080 and concerns about secondary poisoning make this control method less favoured by the RNRP team. The stations also have to be modified by putting in an obstacle wall that made the entrance to the bait into a kinked tunnel. This was to prevent native birds such as weka being able to reach the bait. On the up side the design of the station keeps the bait dry and up off the ground making it seem more appetising to rats and it has had a certain amount of success. However it did not bring the rat population down to target level so it was decided in 2000 that the bait station was not effective enough to warrant the risk of secondary poisoning.

2, snap trapping. From the beginning of 2000 to the end of 2007 this method of rat control was trialled. A normal rat trap was mounted on a metal sheet and slipped into a wooden box/tunnel. Being mounted on a metal sheet made for easy handling of the trap and the box stopped other animals tampering with the trap. The snap trapping had moderate success and had a lower risk of affecting native animals than the 1080 toxin method but on its own it was not effective enough to bring the rat population down to target to the level. It was decided for the 2008 year to trial a new bait and bait station; however there werent sufficient funds to cover the cost and no rat control methods were undertaken for the next 2 years.

How the RNRP has Effected the Ecosystem

When DOC first began the Rotoiti Nature Recovery Project the beech forest and surrounding area were overrun with pests. The population numbers and densities of native birds and insects were very low. Plants such as the two native mistletoes had an extremely low reproductive success rate resulting in no juvenile plants to carry on the next generation. Wasps had monopolised the honey dew and it was impossible to rest your hand on a honeydew producing beech tree without being stung by the wasps that carpeted it. High densities and numbers of rats, stoats and possums meant that bird mortality rates were high and the percentage of successfully raising a chick to adulthood was very low, too low to cover the death rate of adult birds. This meant that the population numbers of many native species were declining in the Rotoiti area. The RNRP was set up to save as much of the biodiversity as possible. For the duration of the project DOC has monitored various species that have been seriously affected by the introduction of pests. These species have been used as a base mark from which to measure their success.

Kaka

Kaka are an excellent way to monitor the effects of the RNRP on the Rotoiti ecosystem as they are affected by all the species that DOC and the FOR have identified as key threats and are working to control.

Two different types of monitoring systems have been used to judge the effect the control of pests have had on the kaka. In the initial stage of the project it was important to establish how successfully the kaka were reproducing and whether any measures needed to be taken to assist the parent birds in raising their young. Therefore, the team of DOC members monitored nests to see how many were able to successfully raise young with the new control measures. The results were compeered with the Rotoroa control free site and monitoring in done in the previous years. (Big Bush was monitored for several years before control measures were put in place, so is it used to compeer the RNRP area with as a what it was like before.)The first method used gives a more accurate idea of how the RNRP has affected the kaka population. The charts bellow show the success of control measures

TABLE 1: COMPARISON OF KAKA BREEDING SUCCESS

BIG BUSH (`85-`96)

RNRP

(1997*)

RNRP

(1998)

RNRP

(1999)

RNRP

(2001)

RNRP

(2003)

No. breading females

?

4

5

4

6

7

No. nesting attempts

19

4

4

6

7

9

No. successful nests

1

4

3

5

4

6

% nesting success

5

100

75

83

57

67

No. chicks fledged

2

12

9

14

10

?#

*this year is a one of as special effort was put into the care of these nests by the RNRP

#report doesnt say

TABLE 2: PRODUCTIVITY OF INDIVIDUAL FEMALE KAKA - RNRP

Six females monitored breeding in the project area.

FEMALE

(AS TX NO.)

COMMENTS

1997

1998

1999

TOTAL

04

No. eggs

No. chicks fledged

4

4

5

5

6*

6

15

15

21

No. eggs

No. chicks fledged

2

1

4

0#

6*

6

12

7

42

Died June 99

No. eggs

No. chicks fledged

2

2

2

2

(dead)

4

4

76

No. eggs

No. chicks fledged

(not monitored)

3

3

?*@

2

?

5

79

No. eggs

No. chicks fledged

3

3

2

2

2

2

7

7

00

Transferred from Whenua

No. eggs

No. chicks fledged

(not present)

(not present)

?@

0

?

0

* two clutches laid that season

# clutch lost to predator just prior to fledging

@ failed at egg stage

TABLE 3: CAUSES OF NESTING FAILURE

BIG BUSH (`85-`96)

RNRP (`98-`99)

ROTOROA (`98-`99)

No. females preyed on

5 (out of 7)

0 (out of 5)

3 (out of 5)

No. nests failed in incubation

12

1

5

No. nests failed in nestling period

1

1

1

Total no. failed nests

18

2

9

Interpreting the charts. Table 1 shows how the control measures put in have increased the success rate of kaka breeding. By Compeering the RNRP area (with control) and the higher success rate seen there, to big bush from 1985 1996 (which had no control during that time) and its very low success in breeding, it shows the positive influence of control in kaka breeding. Also showing this is the link between drop in breeding success rates in 1998 when control measures were reduced and again in 2001 when they were reduced still further.

Table 2 shows how, with lowered predation and competition, females are more likely to invest more energy in egg laying (females 04 and 21 laid more than the average of 4 eggs).

Table 3 shows that no females at the RNRP site were killed by predation, whereas many in uncontrolled areas were killed and most of the nests failed.

The reason pest control measures improved the success rate nests is because of the harmful effects those predators were having. Wasps were monopolising the honeydew. With this competition removed adult kakas were able to again use this resource. Females in particular benefited as the honey dew provides a needed boost of energy in the breeding season for reproducing. Mustildae, rodents and possums were killing adult birds and eating their eggs.

With the lowered predation caused by the RNRP control methods more females were alive to reproduce and were safer from predation while incubating their eggs (when females are at there most venerable). More eggs were able to develop and hatch, chicks were more likely to survive and young birds could mature to breeding age. Kakas only breed in seasons when there is beech seed available in autumn. Rats pose as another source of competition for kaka by eating the beech seed that they need to have in plentiful supply to even attempt to breed.

Kaka did not attempt to breed in the 2000 and 2002 because there was not a large enough seed fall in those years. In 2001 and 2003, though, there was a large beech fall and because of the control of rats the kaka were able to monopolise the larger availability of food that without control the rats would have already increased their numbers to exploit. Being able to exploit the beech seed means that the kaka can reproduce greater in numbers with higher success rates. All this leads to a healthier and larger population of kaka.

A negative effect of the RNRP is that when poison is used in the control of rats and possums (despite the precautions and modifications in trap use) there have been 2 recorded examples of young kaka consuming the bait with fatal consequences. Over all, though, the poison control of rats has been to the kakas advantage. (DOC has also reduced their use of poison)

Flying Insects

Insects are threatened by wasps while wasp larva are in the stage of development that requires food to be high in protein. During this time wasps will head out in droves to hunt native invertebrates to feed their young.

DOC shows no tables for the monitoring of flying insects but dose report that flying insects are showing a gradual increase in numbers. It is very difficult to measure with certainty an increase in insects due to the great variability seen in their numbers in other areas, however reputable scientists such as Sandlant have indicated that it is highly likely that there is a sustained increase occurring in native flying insects. Thus without the intense predation of wasps during the summer months more adults are alive to reproduce and so the reproductive success rate of insects is greater than the mortality rate. Many native birds depend on insects as part of their food source and the increased numbers of insects has lead to a larger population of birds with higher breading success.

Ground Invertebrates

Native invertebrates such as land snails and native weta are preyed on primarily by wasps, hedgehogs and possums, but are also eaten by rats and stoats. With the introduction of species that prey on them weta and snail numbers declined. With fewer adults to reproduce there were not enough young being born to cover the mortality rate increased by higher predation. With the control measures put in place by the RNRP predation levels have dropped and the number of land snails has increased as the number of snails dying had decreased. Researches also discovered a number of smaller snails indicating successful breading. The greater increased number of small shells also shows that the number of snails being born is increased with more adults surviving to reproduce. Two new and rare species of weta were found at Rotoiti after the control measures were put in place (in addition to increased numbers of the weta species already living there). The proportion of increase also seems to be in relation to fluctuation in predator numbers; however that has not been proved. Land invertebrates are also an important food source for birds and the increased number of insects has allowed the bird population to increase and more successfully reproduce as food is more plentiful and easier to find when there is a greater density of insects serving as food.

TABLE 1. NUMBER OF LIVE POWELLIPHANTA SNAILS FOUND IN THE SEARCH PLOTS

Date

Tussock

Bush Edge

Bush

30/04/97

11

2

-

21/04/99

10

-

0

26-27/03/03

19

9

0

Honeydew

Honeydew is produced by a native scale insect. The insect lives of the sap produced by beech trees. To get at the sap it inserts its mouth part into the tree and then it degenerates into a stationary parasite stiffening the sap of the tree. The insect though does not use all the energy in the sap so the modified excess sap is excreted out of the anal filament. This product, honey dew, forms a droplet at the end of the filament. Over time, as evaporation occurs, the honeydews concentration increases meaning there is more energy in the drop. When the drop is taken away a new drop quickly forms, but is not as concentrated as it has not yet gone through the (Bell birds feeding on honeydew )evaporation process. Honey dew is an important food resource for many native birds such as the kaka, tui and bellbird (these birds are known as honey birds). This resource is especially prized during the breeding season as it gives females easily accessible boost of energy and that may assist them to successfully reproduce. Because honeydew is easily available and is high in energy it means that birds can spend less time looking for food and more time in other activities including singing and social activities. It is theorised that spending more time socialising with their mate allows the two to communicate better and in the breeding season this familiarity helps them to raise their chicks more successfully. Honeydew is only a viable food resource for birds when the energy it contains is above 2500J/m and wasps monopolisation of the resorce lowers the energy consentration bellow this point. The RNRP has affected honey birds by lowering the number of wasps and thus the competition for the honey dew resource (see the graphs). The greater availability of honeydew to the honey birds has allowed them to return to behaviour closer to what it would have been before the introduction of pests. Therefore their adaptations are becoming more effective again as environmental conditions become closer to what these adaptations were best suited for. With increased effectiveness of (HONEYDEW ENERGY LEVELS 98/99 (NOVEMBER-APRIL))adaptation successful breeding and survival are increasingly likely.

Some insects such as moths also rely heavily on honeydew, if not entirely. The fact that wasp populations have drop due to the RNRP and are therefore providing less competition for honey dew has allowed the (HONEYDEW ENERGY LEVELS 99/2000 (NOVEMBER-APRIL))population of these moths to increase in number and density. Moths are part of the diet of many birds; therefore increase in moth numbers has allowed the number of these birds to increase as a result of more food that is easier to find, making reproduction easier as the birds are healthier and more able to feed their young.

Flow on effects in bird biodiversity

With the increased number of insects that form an important part of the Rotoiti food web there is opportunity for birds to reproduce and successfully raise more chicks. The fact that there are also now fewer predators preying on adult birds and eating eggs and chicks also provides more opportunity to survive to raise young and do so successfully. RNRP control of competitor species such as rats has also allowed another source of food, seeds, to become increasingly available as a means to survive and feed young. DOC began to monitor the numbers of a variety of bird species to see the effect of the RNRP on birds and also the forests health. The form of monitoring used is the 5 minute bird count where scientists will monitor the number of different species present in an area in 5 minute samples. although the 5MBC has its limitations, it still remains an effective method of monitoring when there is a time constrant.

Shows a reasonable increase in numbers they have reacted well to the RNRP

Have shown slow increase under the RNRP although there has been a drop in numbers in recent years this is probably just due to natural fluctuation. The overall trend is upwards.

Unaffected by RNRP they are showing a continued decrease in numbers.

This chart showing increase in kaka numbers should really be in the kaka section but fits just as well here.

Although pied tit numbers have continued to decrease most other native birds have reacted positively to the RNRP and follow similar patterns of increase to the bellbird and south island robin. This increase in native birds has had further flow on effects with native plants.

Native mistletoe species have a very specific way in which their seeds have to dispersed in order to successfully reproduce. A bird must eat the berry that the plant produces. The seed then passes through the digestive track of the bird and is then pooed (for want of a better word) onto the trunk of a young beech tree. It is important that the berry is eaten by a bird so that 1, it is more likely the seed will land on a young beech; and 2 a birds digestive track is not strong enough to destroy the seed only to simulate the seed case to turn in to a paste that will stick the seed to trunk of the sapling.

Before the RNRP was started possums were eating the berry and if their digestive track didnt destroy the seed they did not excrete the seed onto a young beech tree. Now that DOC and FOR are controlling possum numbers and bird numbers are increasing it is now possible for the mistletoe berry to go through the process required for successful reproduction.

Other plants are also benefiting from the reduction in possum numbers. Possums can kill young trees by over browsing the new shoots; they also lower the number of healthy trees in the area (also by eating the new shoots). So with the lower possum numbers cause by the RNRP there are more trees surviving to adulthood and those that do are also healthier and have more leaves to photosynthesis. This in turn heightens the energy that beech trees can produce and this increase in energy is translated into ability to produce seed. This has several run on effects. First there are more young trees growing up to replace the old. With more young trees mistletoe is more likely to be able to land on the young tree it needs to reproduce successfully. Birds that feed on beech seed also benefit as the greater availability of seed leads to a greater carrying capacity and more resources to monopolise to reproduce more successfully.

Due to the reduction in predator and competitor numbers the environment is safer for native animals and it has been possible for DOC to reintroduce a population of great spotted kiwis. These birds have successfully taken a hold in Rotoiti and their population has increased as they can access the resources of native invertebrates and are less likely to be affected by predation. The kiwis now add to the number of different species living at Rotoiti.

There have been some draw backs caused by the RNRP such as the poisoning that has in the past occurred to the occasional kaka that have somehow accessed poison bait. Sometimes also curious birds such as weka have been killed in stoat traps. However, the increase in the numbers of native animals and plants as well as DOC being able to reintroduce kiwi into the area have cause the biodiversity and health of the ecosystem to increase.

Therefore in consideration of the material presented it has been shown that the work DOC is doing in the RNRP has overall benefited the biodiversity of Rotoiti in the past and will continue to do so as long as the work continues.

Some interesting facts and developments

When DOC controls the population of rats and stoats it is important for them not to upset the balance between their numbers. Kill too many stoats and the rat population becomes impossible to control. Kill too many rats and the stoats will start to target native birds and insects as their primary food source.

RNRP is now artificially implanting mistletoe onto young beech trees. None of these plants have been planted in the wild and it will be several years before they are old enough. The results are eagerly awaited.