Update on Perth River Valley Work Programme – November 2018

In August this year we reported that the aerial predator removal phase of our programme of work in the Perth River valley had been delayed, because weather and snow conditions (experienced and forecast) had reduced our ability to fully implement the ‘1080 to Zero’ method to completely remove possums (and potentially rats). The aerial operation was originally scheduled to be carried out during winter 2018, but we now intend to carry out this work from March 2019.

The decision to delay  this operation provided us with an opportunity to continue to develop and build confidence in strategies to (i) minimise potential risks to kea from the removal operation, and (ii) completely remove possums and rats, and prevent them re-establishing in the area.

Reducing risks to kea from the aerial predator removal operation

During the last two months we have been carrying out trials to assess the effectiveness of two measures to reduce the potential risk to kea from a ‘1080 to Zero’ operation.

The use of tahr carcasses as an alternative food source or ‘distraction’ from baits

In late June we began a trial to quantify the extent to which providing a small number of tahr carcasses as an alternative food source or ‘distraction’ could reduce consumption of toxic baits by kea. The carcasses of 21 tahr (shot with a high powered rifle) were initially placed at approximately 1km intervals along the upper boundary of the 1080 to Zero treatment zone, in order to ‘lure’ kea away from baits. Each carcass was placed as high in the alpine zone as snow and weather conditions would allow. Over subsequent weeks, we replaced any heavily scavenged carcasses to maintain their availability to kea as a food source.

Kea activity at each tahr carcass was monitored using trail cameras. These camera observations during the last four months have confirmed that the carcasses are highly attractive to kea, with 56% of the banded kea population within the research area (i.e. 31 out of 55 banded birds) appearing on camera at tahr sites. Based on a mark-recapture analysis, we estimate the population of kea visiting these tahr sites during this period to be 53 birds (42-79 birds, 95% C.I.).

Four kea feeding at a tahr site, including one of the birds in our banded population (second from left) and one from our radio-monitored population (second from right)

A minor scuffle between two kea at a tahr site

Six kea feeding at a tahr site

An additional small-scale trial, to be carried out from November 2018, will involve placing tahr in known kea locations (within the research area) with and without non-toxic prefeed baits (which do not contain repellent), and monitoring kea behaviour using trail cameras.

If these trials continue to show sufficient promise, we intend to place a small number of tahr carcasses outside the 1080 to Zero treatment zone, but still within the research area, to lure kea well away from toxic baits during the aerial predator removal operation.

The use of repellents to discourage kea from eating baits

The objective of this work is to quantify whether repellent laced bait could discourage kea from eating bait and, if so, devise a strategy to use repellents when the aerial predator removal operation is carried out.

Beginning in July, we applied non-toxic prefeed bait containing a repellent, anthraquinone, along a narrow section of the alpine boundary of the research area. We are currently analysing camera footage of kea behaviour, in order to understand whether the baits are having a repellent effect (i.e. if individual marked birds reduce their interaction with the baits, this would indicate that the repellent is working).

We are also working with a bait manufacturer to produce non-toxic baits containing anthraquinone at a range of concentrations, for trials with captive kea at Willowbank Wildlife Park. These trials are intended to determine the optimal concentration of anthraquinone required to guarantee that the birds experience a short-term feeling of illness, and learn to associate this with the baits. These trials are expected to begin in early November.

Assessing the effectiveness of rivers as natural barriers to possums, rats and stoats

In April this year we began a trial to determine the likely rate of invasion by rats across the river boundary, using a 3.2km long section of the Perth River as the trial site.

We established a network of 128 ZIP automated lure dispensers at 25m intervals along the true left side of the river, lured with mayonnaise that contains the bio-marker rhodamine B. To confirm uptake of the biomarker within the resident population, we undertook two rounds of trapping, each over multiple nights. The results indicated that 82% and then 90% of the trapped rats had ingested the bio-marker. Based on these results, it is very likely that we will be able to identify any rats that do manage to cross the river. We are also pleased to note that the mayonnaise, a new lure we are testing, appears to be both attractive and palatable to rats, possums and stoats.

To date 75 rats have been trapped on the true right side of the river, none of which have shown signs of rhodamine B, which typically shows up as a glowing ‘band’ in whiskers when observed under a fluorescence microscope.

We are now planning further trials in the Perth River research area to determine the rate of rat and possum invasion across different sections of the ‘river barrier’, particularly in summer conditions or where the rivers are braided, shallow, or slow-moving.

These trials will help us to design the layout of traps and devices required to reinforce the river barrier in a range of conditions.

Learning more about what we’re up against

Elevation of possums and rats

In March and April this year we carried out monitoring to assess the relative abundance of possums and rats in the Perth River research area.

Analysis of the results of this monitoring also provided us with some insights into how high into the alpine zone these species are present. This information is helping to inform the baiting strategy for the upcoming 1080 to Zero operation in the Perth Valley, and the extent of the detection network required to detect survivors and invaders.

We established a total of 12 monitoring lines throughout the 7,500ha treatment area, each 500m in length and positioned evenly across different vegetation types and elevations, between 290 and 1,600m. Lines were widely spaced, to ensure individual animals were unlikely to encounter devices on multiple lines. Motion-sensing cameras were deployed at 100m intervals along each line, for a total of 7 days.

The camera footage gathered during this trial showed us that possums are present above 1300m (i.e. in heavy snow) while rats have not yet been seen above 1100m.

We intend to repeat this monitoring in late summer 2018, prior to the aerial removal operation, to determine seasonal variations in the population and the distribution of possums and rats.

Developing a lean detection network for stoats

A network of 124 trail cameras were also installed throughout the research area over winter, at a density of 1 camera approximately every 35 hectares – we refer to this as a ‘lean network’. The camera sites are lured with mayonnaise, delivered using the ZIP automated lure dispenser.

Approximately one quarter of the camera sites have seen stoats. Half of the sightings occurred within the first 7 days of deployment. Approximately one-third of these cameras recorded multiple visitations (although it is unclear whether these represent repeat visits from individual stoats, or multiple stoats).

Further trials using marked stoats are proposed (either at Perth Valley or at our Bottle Rock peninsula field site), in order to observe their behaviour and better understand the likelihood that individual stoats will re-visit camera sites that provide a food ‘reward’ (e.g. food dispensed from an automated lure dispenser).

More information

For more information about this work, and about ZIP’s broader research and development programme, please visit the following two sections of our website:

1. Findings, which detail new developments and key areas of learning; and

2. Updates, which provide information about progress with our work programme.

We also recently published our 2017-18 Annual Report, which summarises our work over the previous year and highlights several key projects that relate to the Perth River valley programme. 

If you have a question or feedback for the ZIP team, please contact us at info@zip.org.nz.

Update on Perth River Valley Project – assessing the effectiveness of a ‘river barrier’ for rats

In 2017, ZIP ran a promising trial in Remutaka Forest Park, which provided strong evidence that rivers are an effective barrier to possum migration.

But what about rats..?

We are currently carrying out a project in the Perth River valley to attempt to answer that very question.

The Perth River research area is bordered to the south and west by the Perth and Barlow Rivers – both fast flowing, rocky, glacial waterways that converge on the southern boundary of the research area.

Since April 2018 we have been bio-marking rats along a 3.2km stretch of the true left side of the Perth River, to enable us to identify whether any rats caught on the true right are likely to have crossed the river (see map below).

This project was designed to be carried out following the completion of a predator removal operation on the true right side of the river, which would provide a ‘clean’ side along which to measure rat crossing events. We had originally intended to complete the removal operation during winter 2018, but this has now been reprogrammed until early 2019.

We are now investigating a range of alternative methods to begin to assess the effectiveness of the Perth River as a barrier to rats, within the near future. The river is at its lowest flow during the winter months, so gaining an understanding of its effectiveness as a barrier at this time of year is important.

As to how we will measure that effectiveness – watch this space for an update soon!

In the meantime, some useful and interesting information has already been gathered from the river barrier project site. To date, we have been able to assess: (i) the relative abundance of rats immediately adjacent to the river on the true left side (to provide an indication of current rat ‘pressure’ on the river barrier), and (ii) whether enough rats will eat the bio-marker to provide robust data for this trial. These findings are outlined below.

Map of river barrier assessment site, Perth River

Measuring rat pressure on the river

ZIP-developed automated lure dispenser containing Pics peanut butter laced with rhodamine B biomarker

ZIP-developed automated lure dispensers were installed on the true left side of a 3.2km stretch of the Perth River in the first week of April 2018. Every 24 hours, these dispensed Pics peanut butter laced with non-toxic rhodamine B bio-marker, which produces a fluorescent band visible under microscope in the growing whiskers of rats after they have eaten it. These were left in place to ‘feed’ rats for a month before measuring rat relative abundance in the same area.

Rat relative abundance is a measure used in predator control to estimate the relative number of rats within an area. This measure, in turn, provides us with an indication of the invasion ‘pressure’ on the river.

Relative abundance was measured over three fine nights along the same stretch of river where the automated lure dispensers were installed. A total of 53 Victor Professional rat kill traps were deployed at 50m spacing, lured with Pics peanut butter, in single entry black corflute tunnels. Results were calculated as the mean number of rats caught per 100 corrected trap nights (C100TN).

A total of 41 rats were caught over the three nights. After accounting for sprung traps, we determined a relative abundance of 39.4 rats/C100TN.

This is a relatively high score and may well be influenced by pre-feeding with Pics peanut butter (via the automated lure dispensers) for a month before trapping. If true, this pre-feeding principle may have wider application in trapping operations, including the Remove and Protect model. If invaders can be cued onto a lure before they invade, they may then be significantly more likely to be trapped using that same lure.

As for the river barrier assessment project, we now have confidence that there are plenty of rats present in the research area, and therefore the ‘rivers as a barrier’ concept remains a real test.

Uptake of the bio-marker by rats

The rat relative abundance survey also enabled us to determine the proportion of rats that were eating from the automated lure dispensers, by looking for evidence of the biomarker in the trapped rats. Whisker samples were taken from 37 of the 41 rats caught, and an additional two rats caught at Scone Hut during the same time period. We analysed those whisker samples under a microscope at Lincoln University, looking for the bright, solid bands of fluorescence from the rhodamine B. If three or more whiskers were found to show traces of rhodamine B, the rat was deemed to have fed on the prefeed from the automated lure dispenser.

Taking whisker samples for analysis

A ship rat showing visible rhodamine B traces in belly fur

A total of 82% (32/39) of rats caught and analysed were found with traces of rhodamine B, meaning this proportion of the resident population (as a minimum) had been feeding from the automated lure dispensers. This is a very encouraging result for the rat river barrier assessment, especially considering that uptake of the bio-marked lure is likely to increase the longer the automated lure dispensers are in place.

Ensuring a high proportion of marked rats is important as it gives us the best opportunity to determine whether any rats caught on the true right side of the river have braved the icy waters to get there.  

Further Update on Perth River Valley Project – possum removal operation

Zero Invasive Predators Ltd (ZIP) will undertake the aerial 1080 predator removal phase of the research and development programme in the Perth River valley from early 2019.

This phase was originally scheduled to be completed during winter 2018, but the forecast weather and snow conditions in the valley are such that we now cannot be confident that the 1080 to Zero method can be fully implemented in a timely fashion, in order to completely remove introduced predators. After consulting with our colleagues from the Department of Conservation it was decided to carry out the aerial phase from early 2019, in order to increase the likelihood of its success.

The weather factor

As detailed in a previous Update, the baiting schedule that is the basis of the 1080 to Zero method is weather dependent. In general, the ideal weather window each time we apply bait comprises one fine, calm day, followed by at least two nights of fine weather. The weather over the past three months has presented very few suitable weather windows. Despite that, we have successfully applied non-toxic prefeed bait on two occasions (on 30-31 May and 21 June).

Weather experts have advised that there is a 70-80% chance of an El Nino weather pattern emerging this spring, which will bring a predominantly south-west airflow, with cooler and wetter than normal conditions predicted for the West Coast. If this pattern does eventuate, then it is unlikely that we will be able to complete the four remaining applications of bait.

Perth River in flood, near Scone Hut (Credit: Briar Cook)

The snow factor

Ideally, toxic bait is not applied on snow that has settled on the ground. Snow can prevent target predators from accessing bait, and the moisture in the snow begins to degrade the bait, making it less effective. 

Considerable snow has fallen within the project area. It is now estimated that the ‘permanent’ snow line, i.e. the lowest elevation of snow not expected to recede until spring, is at approximately 1,250 metres above sea level.

Intermittent snow storms are likely to continue to bring snow to lower levels, where it will melt away. The image below shows snow conditions around one of the temporary bivvies located at approximately 800 metres above sea level.

Snow at 800m above sea level, 23 July 2018 (Credit: Chad Cottle)

Comments

The programme of work we are undertaking in the Perth River valley is research and development. We are focused solely on developing and refining a new way of tackling the predator management challenge, in an attempt to halt, and ultimately reverse, the decline of our native species. We are making good progress, but there is still much to do and learn along the way.

It is important to acknowledge that the fundamental nature of research and development is that there is inherent uncertainty, and risk. In this case, we are no longer confident that proceeding with the 1080 to Zero operation under current and forecast snow and weather conditions will deliver the predator-free results sought.

Between now and early 2019, we will continue to test and refine techniques to reduce potential impacts on kea (in association with Department of Conservation scientists), and increase our confidence in successfully delivering the Remove and Protect model in the Perth River valley.

Update on Perth River Valley Project – possum removal operation

Zero Invasive Predators Ltd (ZIP) has received permission from the Department of Conservation (DOC) to proceed with the aerial 1080 phase of our programme of research and development in the Perth River valley, but weather and other conditions currently prevent the operation going ahead for the foreseeable future.

The permission will enable us to maintain our efforts to develop a promising new approach to completely and permanently remove introduced predators from large mainland areas, in order to help New Zealand’s native biodiversity to thrive.

If successful, the approach will have particular relevance for the more than one million hectares of similar landscapes in South Westland.

The permission is conditional on ZIP completing two actions in the treatment area to minimise the risk to kea, namely: (i) locating tahr carcasses to provide an alternative food source and foraging focus, and (ii) applying non-toxic repellent bait to induce an aversion to cereal baits, prior to applying the toxic bait.

Since the inception of the programme of work, we have worked with kea experts from the Department of Conservation to identify and minimise the risk to kea of the programme of work in the Perth River valley. 

We’re very grateful for their help. And we’ll continue to strive to help kea flourish, both locally and nationally.

As for when the aerial operation will go ahead, the application of the predator removal approach is subject to local environmental conditions, particularly wind, rainfall and snow cover.

We will not proceed with the aerial 1080 operation until we are confident that it will completely remove all possums and significantly reduce rats and stoats. The current conditions in the Perth River valley are, however, not suitable to proceed with the aerial 1080 operation for the foreseeable future.

Update on Perth River Valley Project – opportunities to reduce risk to kea

Updated Wednesday 19 July 2018

Zero Invasive Predators Ltd (ZIP), with the support of the Department of Conservation (DOC) and Predator Free 2050 Limited, is currently undertaking a programme of research and development work in the Perth River valley on the West Coast of the South Island.

The purpose of the work is to test and refine an approach to completely remove possums from large areas and prevent them from re-establishing, and to develop this approach for ship rats and stoats. We call the approach ‘Remove and Protect’. This is the first time such an attempt has been made on the New Zealand mainland. The results are expected to help enable New Zealand to achieve predator-free status by 2050.

The Perth River research area contains kea, which is a nationally endangered species. The purpose of this Update is to outline some new measures that we are progressing to mitigate potential impacts on kea of the work underway in the Perth River research area. 

Background

Kea are the world’s only mountain parrot and considered by scientists to be one of the most intelligent bird species in the world. The national population of kea is expected to decline by 50-70% over the next 10 years unless the causes of decline are addressed.  Predation by introduced predators like possums and stoats is considered one of the key reasons for the decline in kea numbers. 

One component of ZIP’s ‘Remove and Protect’ approach that is being tested and refined in the Perth River research area is the use of a method called ‘1080 to Zero’ to completely remove predators.

Predator control using aerial 1080 has an overall beneficial impact on kea nesting success. In one recently published study, kea nest survival at a monitored site increased from 46.4%, before the application of 1080 to 84.8% after the application of 1080 (Kemp et al. 2018). 

However, kea have an inquisitive nature, and some kea have died as a result of 1080 poisoning. Consequently, from its inception, the research and development work programme in the Perth River valley has actively considered ways to reduce risk to kea. 

Steps already taken to reduce risk to kea in the Perth River research area

Minimising the risk to kea was part of the decision making process when it came to deciding the location of the Perth River research area. We reduced the size of the original proposed research area from c.20,000ha to 12,000ha, to lessen the number of kea exposed to 1080 baits (the 1080 to Zero treatment area is only 7,500ha).

The research area was located as far as possible from the nearest kea scrounging site, Franz Josef township, which is 28km away at its closest point. We also selected an area that had a history of aerial 1080 operations – in this case five operations since 1997. The site was also selected on the basis of a number of other criteria related to our research requirements.

Since then, 30 kea have been fitted with radio transmitters (and another 25 have been banded) to monitor the impact of applying aerial 1080 on kea mortality and breeding success. Radio-tagged kea are scheduled to be monitored (using a light aircraft) after each application of prefeed and toxic bait. Monitoring was done after each of the two prefeeds that were applied on 30-31 May and 21 June.

We also recently completed a project to estimate how likely kea would be to consume baits, in order to assist DOC to decide whether the toxic bait application should proceed. In summary, the results confirmed what was already known - i.e. that kea interact with bait. However, owing to the small sample size, it was not possible to make a specific estimate of the likely level of actual consumption of toxic bait. 

Two new measures to mitigate potential impacts on kea

It was originally estimated that around 18 kea were likely to be present in the research area. During the course of our work, we discovered that there is a healthy population of approximately 75-100 kea in the research area. It is likely that the current population of kea can be partly attributed to the benefits of the previous five applications of aerial 1080 in the area.

We are committed to doing all we can to reduce the risk of kea mortality in the event that the decision is made to apply aerial 1080. Recently we have initiated two new measures to help achieve this.

Discourage kea from eating 1080 bait

To reduce the risk of birds consuming toxic bait, we are attempting to enable kea to learn that eating bait is not good for them, by applying non-toxic prefeed bait containing a repellent, anthraquinone, that makes them feel sick, before any toxic bait is applied.

Anthraquinone is a secondary repellent in that it has no smell or flavour, but makes birds feel sick after consumption. By associating the bait with the source of illness, birds will be less likely to eat it in future.

On Saturday 14th July, with the permission of the Department of Conservation, green-dyed baits laced with anthraquinone were applied within a thin band along a section of the alpine boundary of the research area.

This non-toxic bait was dyed green, in order to resemble the toxic bait as closely as possible.

We may reinforce any repellent effect with a repeat application of repellent bait, immediately prior to toxin baiting. The thinking behind doing this is that the more times kea have the opportunity to learn to avoid the bait, the greater the chance that they will avoid it in future.

Provide tahr carcasses as alternative food/distraction

Our field staff have observed, and there is substantial anecdotal evidence, that kea in this area already quickly locate and utilise dead tahr (either left by hunters or dead from natural causes) as a food source.

On Friday 29 June, the carcasses of 21 tahr shot by a DOC ranger (using a high-powered rifle – not lead shot), as part of a DOC’s wider programme of tahr control, were placed at approximately 1km intervals along the upper boundary of the 1080 to Zero treatment zone, in order to lure kea away from the baits.

Kea activity at each tahr carcass is being monitored using trail cameras, in order to help us understand whether this approach plays a role in limiting any impact from the aerial operation. Our staff have already observed a number of birds visiting the carcasses.

There is strong evidence to suggest that the risk to kea of secondary poisoning (i.e. from eating the meat of animals that have been poisoned by baits) is much lower than the risk of primary poisoning (i.e. from eating baits) following an aerial 1080 operation (van Klink and Crowell 2015).

Furthermore, it is not known if aerial 1080 impacts tahr. This is being investigated as part of a Game Animal Council-led project connected with the proposed aerial operation in the Perth River research area.

We will continue to record activity at the tahr sites from now until any toxic bait is rendered safe. From this data, it should be possible to determine whether or not the kea maintain interest in the tahr carcasses in the presence of bait.

Final thought

DOC is currently reconsidering the permission for ZIP to apply aerial 1080 as part of the Perth Valley research project.

Ultimately, the decision about whether to apply aerial 1080 in the research area will balance the risk of individual kea mortality against the potential population benefits to kea (and other native species) in the research area, as a result of predator removal, and the benefits of continuing to test, refine and develop the Remove and Protect approach and its potential contribution to a Predator Free New Zealand.

We will continue to provide updates via the ZIP website as this work progresses.

Reference

Kemp JR, Mosen C, Elliott GP, Hunter CM. (2018). The effects of aerial poisoning for pest mammal control on the productivity of the kea (Nestor notabilis). New Zealand Journal of Ecology 42.

Van Klink, P. A., & Crowell, M. D. (2015). Kea (Nestor notabilis) survivorship through a 1080 operation using cereal baits containing the bird repellent d-pulegone at Otira, central Westland. Publishing Team, Department of Conservation.

Update on Perth Valley Project - results of pre-operational monitoring

Background

Preparations continue for implementation of our ‘1080 to Zero’ operation in the Perth River Valley, South Westland. The objective of this operation is to completely remove possums (and potentially ship rats). The operation is also expected to have a substantial effect on the local stoat population; however, to what extent remains unknown.  In order to evaluate the success (or otherwise) of our operation, we need to have an understanding of relative abundance of these target species in the site pre-operation. So, at the end of March and early April, we undertook to measure the relative abundance of possums, rats, and stoats within our project area.

We also took the opportunity to measure the presence of non-target species within the area, in order to estimate whether these species are affected by the aerial operation.

Measuring predator relative abundance

The Perth River Valley site consists of 12,000ha of mountainous terrain, surrounded by substantial rivers and glaciers, up to 3,250m in elevation at some locations. An area of approximately 7,500ha within this site will be aerially treated with 1080.

Within this area a total of 12 monitoring lines were deployed, each 500m in length and positioned evenly across different vegetation types and elevations, between 290 and 1,600m. Lines were widely spaced, to ensure individual animals were unlikely to encounter devices from multiple lines.

We followed the National Pest Control Agency (NPCA) standard guidelines for monitoring possums and mustelids (in this case, stoats and weasels), and DOC standard protocol for rats.

Tracking tunnels were placed along lines at 50m intervals for rats. Tunnels were placed at 100m intervals for stoats, accompanied by motion-sensing cameras (positioned over tracking tunnels).  WaxTags™ were used for possums, deployed at 20m intervals along a 200m stretch of each line. Each monitoring line ran for 7 days. Rats were tracked on the first day, followed by three days of camera trapping and tracking for stoats. The full 7 days were used to monitor possums.

Measuring the non-target species

The same camera traps used to monitor stoats were also used to monitor the activity of various non-target species within the site. We deployed these cameras three weeks prior to the one-week abundance index surveying of target species. Cameras were not lured during this time; however, because many species prefer to follow cut tracks, the cameras were well placed to capture a variety of species.

Relative predator abundance results

In total, 59 out of 60 camera traps remained functional throughout the pre-operation target and non-target species surveys. Using the standard protocol for each target species, our results were:

• 48% possum chew across site (58/120 WaxTags),

• 12.5% tracking of rats across site (15/120 tracking tunnels), and

• 1.7% stoat tracking across site (1/60 tracking tunnels).

Stoat exiting tracking tunnel, 18 April 2018

Camera traps were used to increase confidence in results for stoats, as recent literature suggests they have a much higher sensitivity for these species than other available detection tools. However, over the course of the three-day survey for stoats, both camera trap and tracking tunnel results were the same.

 

Comparing the industry standard with camera detections

Camera traps used during the non-target species survey period were left running during the one-night tracking tunnel index for rats. When comparing only the 60 tracking tunnels paired with camera traps during this time, a total of 10 cameras across the site detected rats (16.7%), compared with only 6 tracking tunnel detections (10%). This result, although a seemingly small difference, shows once again the sensitivity of camera traps, even for smaller species such as rats.

We also observed numerous rat encounters over the course of the three-week non-target species camera survey (Table 1). Many recent studies have suggested that the length of time for device deployment is highly influential on the probability that it will detect an animal. For instance, looking only at the three days prior to the standard one-night tracking index for rats, a total of 17 cameras detected rats. Over the course of the three weeks in total, 29 out of the 60 cameras detected rats; stoats were detected on 11 cameras, and possums were detected on 37 cameras (Table 1). 

Table 1 Standard index monitoring and camera trapping results

Non-target species seen on our camera network

During the three weeks of pre-operation camera trapping, we found chamois (on 7 cameras), deer (6), Kea (2), Tomtits (3), South Island robins (7), black birds (5), and a weasel (1) on camera.

South Island robin, 24 April 2018

Chamois, 24 April 2018

The Perth Valley Project - what is it all about?

As reported in previous updates, we have recently begun working in collaboration with the Department of Conservation and Predator Free 2050 Limited on a new research programme at a 12,000 hectare site within the Perth River Valley (South Westland).

Earlier this month we worked with West Coast Film to produce a short video about this ambitious and exciting programme of work, which aims to completely remove possums (and potentially rats) from the site and prevent them from re-establishing.

For further information, please contact us at info@zip.org.nz.

Update on Perth Valley Project - May 2018

In January we reported that Zero Invasive Predators (ZIP), in collaboration with the Department of Conservation and Predator Free 2050 Limited, had started a new research programme in a 12,000 hectare area within the Perth Valley (South Westland).

The programme aims to develop an approach to completely remove possums from large areas and to prevent them from re-establishing. Possums are the initial focus of the research, but the programme will also seek to develop the approach for ship rats and stoats.

Infrastructure

Over the past few months, a small field team has been based within the Perth Valley project area. They have been establishing temporary routes to allow ease of access for ZIP staff in the project area. These routes are well below the standard of a traditional tramping track.

Three temporary bivvies are being built (in Oamaru) to provide accommodation for the field team. Once completed, the bivvies will be transported to Whataroa, and then heli-lifted onto their foundations (which are already installed), most likely during mid-May.

Satellite-based internet has been installed and working at Scone Hut, for research purposes, and will be installed at each of the three temporary bivvies.

A very high frequency radio repeater has been installed which now provides reliable radio communication across the research area for the team.

A predator gate has been installed on the Scone River swing-bridge to block possums, rats and stoats from accessing the project area. This gate is never locked and does not prevent access by people.

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Radio repeater, Perth Valley

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Predator gate, Scone River swing bridge

Complete removal of predators

DOC and the Medical Officer of Health (MOH) have recently granted ZIP permission to apply aerial 1080 at this site.

The treatment area covers approx. 7,500ha. The area to be treated includes alpine shrublands and tussocklands, because this is habitat for possums, stoats and rats. One of our field team recently took the video below of a stoat with a rat in its mouth in this habitat.

We anticipate that this operation will result in the complete removal of possums, and maybe even rats, from the research area. (Stoats are also expected to be greatly reduced; the full extent of that is less predictable and will be the subject of research).

The 1080 to Zero prescription we will use involves the following baiting schedule:

Phase 1 – early-late May (weather dependent)

Prefeed #1:   2kg/ha Wanganui #7 non-toxic 6g bait (orange lured)

Prefeed #2:   2kg/ha Wanganui #7 non-toxic 6g bait (orange lured)

Toxin #1:         4kg/ha Wanganui #7 0.15% 1080 6g bait (orange lured)

Phase 2 – early-late July (weather dependent)

Prefeed #3:   2kg/ha RS5 non-toxic 6g bait (cinnamon lured)

Prefeed #4:   2kg/ha RS5 non-toxic 6g bait (cinnamon lured)

Toxin #2:         2kg/ha RS5 0.15% 1080 6g bait (cinnamon lured)

If the 1080 to Zero treatment is successful, and we also successfully develop techniques to prevent possum and rat invaders from re-establishing, then the large-scale repeated application of aerial 1080 may no longer be necessary at this site (and could well be deployed at similar sites throughout New Zealand).

You can read more about our previous work to develop the 1080 to Zero prescription here. 

Monitoring non-target species

The research programme also includes work to investigate the impacts, if any, of the 1080 to Zero treatment on four non-target species: kea, whio, rock wren, and tahr.

Kea

We have fitted 29 kea within the project area with radio transmitters that alert staff if a transmitter has not moved for over 24 hours (indicating potential death of the animal wearing it). The kea will be monitored using Sky Ranger, a receiver mounted within a fixed wing aircraft, after each application of bait (i.e. pre-feed and the toxin).

Rock wren

As part of the work to fit kea with radio transmitters, we discovered that rock wrens are present in the research area in relatively large numbers compared to other similar sites.

With the assistance of DOC staff, we have started to visually survey rock wren numbers in selected parts of the alpine zone both within and outside the aerial baiting area. These surveys will be repeated after each of the two applications of the toxic bait (snow level allowing).

Whio (blue duck)

Sections of the Barlow, Perth and Scone Rivers, and the Bettison Stream will be surveyed by field rangers for the presence of whio. This survey will occur before the first toxic baiting, and after each toxin application to determine presence or absence of the birds.

Radio tags cannot be used in this instance, as the rivers in which the whio live are too dangerous for staff to access to catch and handle the ducks.

Tahr

A monitoring plan has been developed by the Game Animal Council, in association with ZIP, New Zealand Deerstalker Association, Professional Hunting Guides Association, and DOC.

A Game Animal Council-led team recently spent one day in the research area, with helicopter support, and attached collars containing radio transmitters to 21 tahr (made up of nannies and young males). These will also be monitored using Sky Ranger (at the same time as kea are monitored).

Measuring the effectiveness of rivers as barriers to rats

In November 2017 we reported on the results of a trial to determine whether a relatively small river is an effective barrier to possum migration. We are now running a trial to determine the effectiveness of the Perth River as a natural barrier for rats.

ZIP-designed automated lure dispensers, filled with Rhodamine B biomarker-laced peanut butter or ‘egg mayo’ (by Connovation) have been deployed along a 3.2km stretch of the river’s edge outside the research area (i.e. the true left side of the river). Kill traps have been deployed along the corresponding river edge inside the project area (the true right side). The rats caught in those traps after the first toxin application will be examined for presence of the biomarker; if it is found, then this will indicate that the rat(s) crossed the river.

Tree-mounted automated lure dispenser, Perth Valley

The lure pictured is Pics peanut butter mixed with Rhodamine B bio-marker

Detection network

Detection of survivors

We are currently using tracking tunnels, wax tags and trail cameras to detect and measure possum, rat and stoat numbers at 12 separate sites in the research area.

In order to determine success of the 1080 to Zero treatment, these tunnels, and cameras will be reinforced with chew cards deployed every 10m along approximately 25 detection lines that are 700m apart from the valley floor to the alpine zone throughout the research area.

Surviving predators, in the absence of others (i.e. 'lonely survivors'), are known to roam widely as they presumably look for mates – as such, we expect this network of devices to detect those mobile individuals. For rats, this network is expected to be able to detect any survivors and their first offspring within 15 weeks of the network being deployed (with 90+% confidence).

We do not expect to be able to reach a final conclusion about the success of the 1080 to Zero treatment until November 2018 at the earliest (weather dependent).

Lean detection network

Assuming the treatment is successful, the research focus will move to protecting the project area from reinvasion. The detection grid for this is expected to comprise of self-reporting traps (i.e. a trap that automatically informs our field team if it is sprung) deployed every 100m along the same detection lines referred to above. This self-reporting function is vital for the long-term management of this trap network over such a large project area.

For further information, please contact us at info@zip.org.nz.

Perth Project and 2018 Tahr Hunting Season - Adams Wilderness Area - Updated 2/03/2018

ZIP, in collaboration with DOC and Predator Free 2050 Ltd, has begun work on a research programme within the Perth Valley (South Westland) to test and refine an approach to completely remove possums from large areas, and prevent them re-establishing.

The 'Q&A' document and map linked below contain further information about how this work may overlap with this season’s tahr hunting experience in the Adams Wilderness Area.

The Department of Conservation is liaising with parties who hold balloted tahr hunting areas for the 2018 season that fall within the research area.

We will update the Q&A document in response to any further questions.

Perth Project and Tahr Hunting Q&A - Updated 2/03/2018

Map of Perth Valley Predator Treatment Area, Huts and Bivvies

Possum, Rat and Stoat Removal Research in South Westland - 26/01/2018

ZIP is beginning work on a research programme at a 12,000 hectare block within the Perth Valley (South Westland), to test and refine an approach to completely remove possums from large areas, and prevent them from re-establishing. The research programme will also seek to develop this predator management approach for ship rats and stoats.

If successful, the approach will have significant beneficial outcomes for native plants and animals in the valley. It could also negate the need for the repeated use of landscape-scale aerial 1080 to control these predators here and elsewhere in New Zealand, and help pave the way for a predator-free New Zealand.

The approach being developed has three main parts:

1. Reinforcing natural barriers to the movement of predators into the block (e.g. rivers, alpine tops) with a network of traps.

2. Completely removing predators within the block. This approach uses a more rigorous method of applying aerial 1080 than standard operations. The operation is scheduled for mid-2018. Approval by DOC and the Medical Officer of Health will be obtained before the 1080 treatment is undertaken. 

3. Detecting predators that either survive the 1080 treatment or reinvade the block from beyond its boundaries, and removing them before they can establish a population.

Possum browse on rata in the research area, Dec 2017

Healthy rata in flower (Photo credit: DOC)

ZIP and DOC staff are liaising with iwi, local people and other users of the valley (particularly hunters) to identify any impacts of the research programme of work on them, and discuss options to reduce any that are identified. These initial conversations with members of the community who are, or may be, directly affected by the planned research are a critical part of the planning process.

Staff are also identifying options to minimise any potential impacts of the work programme on native species including kea. Any negative impact on kea from the aerial 1080 work is expected to be small, and a sample of kea will be radio tagged and monitored through the operation in order to measure this. The kea population is expected to benefit from the combined and prolonged effect of the possum, rat and stoat removal, and ongoing protection of the site from reinvasion.

Possums are the initial focus of this work because:

1. they are known to prey on native bird species, and their eggs, including kereru and kea, as well as invertebrates such as wētā;

2. they are the major cause of the decline of trees such as kāmahi and rātā; and

3. the results of similar research at smaller sites suggest it is likely that the approach described will be successful.

The Perth Valley was selected for this research because the rivers and streams and alpine tops are expected to be strong natural barriers, and the area contains valued biodiversity; forests are dominated by kāmahi and rātā, while a full range of native birds are found in the area, including threatened species such as kea and whio/blue duck. 

Additionally, ZIP’s existing working relationship with local DOC staff, and a recent track record of successful trials in similar habitat, set a strong foundation for the programme of work.

The indicative boundaries of the research area are shown on the map below:

The work programme will be evident in the research area through:

1. The presence of ZIP field staff, who will be regularly flown into the site as they establish the required infrastructure and carry out the research programme.

2. The installation of traps, as well as detection devices such as chew cards and motion-sensor cameras.

3. The installation of satellite communication facilities at huts and establishment of some temporary routes and accommodation, for ZIP and DOC staff.

4. The installation of predator gates on swing-bridges (which will not prevent access to the site by people).

Download a print-ready information sheet about the research programme.

This work is a collaboration between Zero Invasive Predators Ltd (ZIP), the Department of Conservation (DOC), and Predator Free 2050 Ltd.

The ZIP/DOC trial in South Westland is now complete

In June 2017, Zero Invasive Predators Ltd (ZIP) began a trial within 2,500 hectares at the confluence of the Jackson and Arawhata Rivers, South Westland, to test whether a modified technique for applying aerial 1080 could completely remove possums, and potentially rats (i.e. not just suppress them to low numbers). Two applications of non-toxic prefeed bait were flown in June, and the 1080 bait was aerially applied on 5 July. Pre-operational monitoring indicated that possums were at 50%, while rat numbers were low. 

Since then, a core area of 400 hectares within the treatment zone has been intensively searched for any surviving possums and rats using chew cards, tracking tunnels and cameras.

By Friday 25 August, 52 days (and over 77,000 'detection nights') after the application of 1080, we had not recorded sign of any surviving possums, or rats! We therefore concluded that our modified technique for applying aerial 1080 is very likely to have successfully completely removed possums and rats at this site. 

Consequently, we have decided that there is no need for a second application of aerial 1080 for the purposes of this trial (we had applied prefeed on the 3rd August in case a second application was needed to target any surviving possums or rats). This trial is now complete.

We have subsequently initiated a second trial at the site, simulating a ship rat incursion into a rat-free area, to determine the spread of a first generation of ship rats (i.e. the Gen One 'footprint') across a forested landscape. The results will help inform the design of tools and techniques to respond to a rat incursion in a timely manner. This project may require the targeted use of aerial 1080 as a ‘spot treatment’ to remove these individual rats.

Update on ZIP/DOC trial in South Westland - 31 July 2017

Monitoring is showing encouraging early results for the Zero Invasive Predators Ltd (ZIP) and Department of Conservation (DOC) trial in a 2,500 ha forest block near Jackson/Arawhata in South Westland.

The trial is part of our work to develop a method to completely remove possums, and potentially rats, from mainland sites. If successful, this method of predator removal will reduce, and ultimately eliminate, the need for repeated wide scale aerial application of toxins to control predators; and provide a tool for progressing New Zealand towards its Predator Free 2050 goal.

Phase One

Phase One of the trial involved two aerial applications of non-toxic cereal ‘pre-feed’ bait in June, followed by a single application of 1080 cereal bait on 5 July 2017, to attempt to reduce predator numbers to ‘functional extinction’ (i.e. the population is no longer viable).

Intensive monitoring in a 400 ha core of the trial block is currently being undertaken with promising early results.  A team of five people are regularly checking 800 monitoring points in the block. This monitoring will continue for approximately 50 days to ensure an accurate assessment of survivorship (if any), and provide confidence around the effectiveness of the method. As at 31 July 2017, no evidence of rat or possum survival has been found.

If no surviving possums or rats are detected after 50 days, then the trial will be complete.

Phase Two

If monitoring does find survivors a second phase will consist of two further pre-feed applications of non-toxic bait and a second 1080 application. The aerial pre-feed applications of non-toxic bait will begin within the initial Phase One 50-day monitoring period, in order to ensure that the Phase Two 1080 operation, if required, happens as close to the 50-day window as possible to avoid any successful breeding by survivors.

The two phases use different cereal baits with different ‘flavoured’ lures to reduce the chance that target individuals learn to avoid the bait after trying it during the first phase. Both 1080 operations will use the same strength toxin.

For more information, please refer to our Fact Sheet on the trial.

Fact Sheet on ZIP trial in South Westland

ZIP and the Department of Conservation are investigating a method to completely remove possums, and potentially rats, from mainland sites.

If successful, this method of aerial predator control will reduce, and ultimately eliminate, the need for repeated wide scale application of toxins to remove predators; and provide a tool for progressing New Zealand towards its Predator Free 2050 goal.

The following Fact Sheet contains information and context about the proposed trial.

For more information, please contact the Department of Conservation:

B Pryor on 027 4064 998, or G Scott on 03 751 0807.       

New video from ZIP's field development site, Bottle Rock peninsula

In this video, a few members of the ZIP team talk about our work at Bottle Rock peninsula in the beautiful Queen Charlotte Sound.

Official Opening of ZIP's predator research enclosure, 9 June 2016

ZIP's new invasive predator research enclosure in Lincoln was officially opened yesterday by Hon Maggie Barry, Minister of Conservation.

This facility will play a key role in enabling us to rapidly develop new technology to remove invasive predators and their impact on our native species and the New Zealand economy.

You can learn more about the new enclosure here and here, and a few photos from the day are shared below. All photos were taken by Rory Harnden.

ZIP would like to extend a huge 'thank you' to all those who made this facility possible, and to those who joined us on the day to help us celebrate its completion.

Attendees arrive at the enclosure.

A taxidermied stoat fiercely guards the podium during speeches.

ZIP Board Chair Devon McLean addresses the group and thanks all those who made the enclosure possible. To his left stands ZIP Business Manager Phil Bell.

Minister of Conservation Hon Maggie Barry addresses the group.

L-R: Francesca Eggleton (Fonterra and Chair of Dairy Industry Working Group), Hon Maggie Barry, Devon McLean

Hon Maggie Barry cuts a ribbon to officially open the new facility.

Tom Agnew (ZIP Animal Behaviour Technician) demonstrates jumping heights of invasive predators next to the 'internal cell' in the enclosure where the team is developing a low profile predator fence for potential application on farms and at dairy production sites.

ZIP Principal Engineer John Wilks demonstrates the prototype automated lure dispenser ZIP is developing along with InFact Design.

ZIP Field Team Lead Duncan Kay demonstrating the 'ZIP-tip' prototype automated detection device to Dr James Ross of Lincoln University.

L-R: James Holborow (DOC), Devon McLean, Hon Maggie Barry, Stuart Pearson (Eleccom Design Limited), Tim Sjoberg (ZIP Animal Behaviour Technician)

Prototype TUN200 trap box (with perspex cover for display purposes), fitted with prototype automated lure dispenser and automated reporting satellite node.

Dacron bedding from female ship rat and male stoat, trialed as a 'social' lure in predator research enclosure with promising results.

The sun sets on our beautiful new enclosure.

A day in the life of a ZIP field ranger

What does a 'typical' day for a ZIP Field Ranger look like? Briar Cook offers us a window on her world in this update from the 'conservation frontline'.

The writer re-caffeinates in preparation for the day ahead... The boxes of eggs to her left were generously donated to ZIP by Koromiko Free Range Eggs for use in our stoat traps.

With winter mornings getting darker, the Bottle Rock field team start the day with a candlelit breakfast. The aroma of industrial strength coffee wafts through the field base, as the team gear up for another day in paradise.

The focus for the week is servicing the defence lines in the Bottle Rock 'virtual barrier', an intensive matrix of devices designed to prevent possums, rats and stoats from entering the protected area on Bottle Rock peninsula.

Pete is on daily leghold duty today, and with clear, still weather the previous evening, he is expecting a few catches. We take the 'side-by-side' all-terrain vehicle and set off up the track to the ridge where our lines begin. As ZIP field rangers, we are armed with trademark fluoro vests, paint scrapers to remove carcasses from traps, various lures, and knee pads the skate pros would be proud of.

Field Ranger Michael Tunnicliff and Field Team Lead Duncan Kay traversing some fairly typical Bottle Rock terrain.

Mike drops me off and I begin my journey down D3, or the third defence line, which also happens to be on the Queen Charlotte Track from historic Ship Cove to our base in Resolution Bay. Traps are intensive here, with several devices every 10 metres, providing maximum encounter opportunities for invading predators. This is where the chunky knee pad pulls its weight – with around 140 double set kill traps on the line, kneeling on rocky ground gets old fast.

View of Motuara Island from saddle lookout on Queen Charlotte Track/ D3.

I hear the morning Cougarline water taxi cross the bay below and anticipate the flow of visitors soon to come over the hill from Ships Cove. It’s a calm, sunny day, and the views from the line are fabulous. As I work, people begin to trickle past. There are young couples, families and mature groups of old friends with walking poles and friendly grins. Many are curious about what we do, what all the traps are for. Most are enthusiastic and supportive, so I spend a bit of time explaining the devices. As they leave I give them a grave warning regarding the presence of weka – the more of these cheeky feathered vandals around, the greater the likelihood that unobserved lunch items will suddenly and mysteriously disappear. I have personally witnessed one run off with a banana belonging to an insufficiently cautious member of the ZIP team who shall here remain nameless... (Ed. note: it was John)

A hungry weka eyes up a peanut butter-baited tracking tunnel.

The local karearea (New Zealand's rare native falcon) screeches overhead, and I spy a kereru in the trees above the next trap, alerted to its presence by a soft ‘coo’. Piwakawaka (fantails) and tomtits flit ahead of me, picking off the insects I disturb as I walk down the track.

A kereru, or native New Zealand woodpigeon, near the ZIP field base at Resolution Bay.

Being amongst the native flora and fauna is a huge bonus for me. My encounters with these little critters are a huge motivating factor in my work. The reason we do what we do is to ultimately make a better world for them to live in, and I’m privileged to be a part of creating better, smarter ways to do that. Even if it means weird smells, soggy boots, maggots, hook grass, bum sliding, bad jokes and washing all our clothes by hand…

'Bottle', the camp goat at Resolution Bay.

Before I know it, the day has crept past, and I’m down at the coast and the last trap for the day. The water is clear and calm, the tide is up and I reckon it’d be a good evening for a fish. I wander back towards base, calling a greeting to the camp goat on the way past, scattering the sheep while trying not to trip over the chickens. The rest of the team trickles in one by one. We exchange victory stories from the 'conservation frontline' and talk about our day, then prep our gear ready to do it all again tomorrow. No complaints here.

The view from Resolution Bay wharf on a still, quiet evening.

Welcome!

Kia ora!

Welcome to the new and improved website of Zero Invasive Predators Ltd (ZIP).

We are very excited to introduce ourselves and begin sharing our world with you: what we are up to; what we have learned so far; and what our future work programme holds.

We’ve kept a low profile to date for a few key reasons:

• We’ve been tasked with an ambitious and exciting technical challenge, which has been our primary focus to date;

• We are still very much in ‘learning mode’, gathering the data (and scientific rigour) to support our observations from the field; and

• We’ve been fortunate to secure sufficient investment for our current work programme from our founding partners, DOC and NEXT Foundation, along with Jasmine Social Investments, Morgan Foundation and a group of Dairy Companies including Fonterra, Tatua, Synlait, Westland Milk Products, Open Country and Miraka.

Starting today, we’ll be providing regular informal updates via this page. More detailed technical updates on our findings will be posted here.

Questions? Comments? We'd love to hear from you!

info@zip.org.nz