Managing animal pests
The Canterbury Pest Management Plan 2018 – 2038 (RPMP) contains five programmes under which declared pests will be managed.
In addition, there are a number of other species which have not been declared pests, however, control of these species may be considered by land occupiers to protect sites where they are impacting on natural biodiversity. These are in the list of other species of interest.
Identified pests and management programmes
For more detailed information please see the Canterbury Regional Pest Management Plan 2018–2038.
What is the Exclusion Programme?
The objective of this programme is to keep pests already present in New Zealand out of Canterbury.
Species included under the Exclusion Programme
|Common name||Scientific name||GNR|
|Koi carp*||Cyprinus carpio|
*Classified as unwanted organisms
What is the Eradication Programme?
The objective of this programme is to eradicate certain pests from Canterbury by 2038.
Species included under the Eradication Programme
|Common name||Scientific name||GNR|
What is the Progressive Containment Programme?
The objective of this programme is to contain or reduce the geographic distribution of a pest in a defined area over time.
Species included under the Progressive Containment Programme
There are currently no species included.
What is the Sustained Control Programme?
The objective of this programme is to provide ongoing control of a well-established pest to reduce its impact on values and prevent further spread to other properties.
Species included under the Sustained Control Programme
|Common name||Scientific name||GNR|
|Bennett's Wallaby²||Macropus rufogriseus rufogriseus|
|Feral rabbit||Oryctoladus cuniculus||Yes|
² Unwanted organisms status expires 20/09/2021
What is the Site-led Programme (Protecting values in places)?
The objective of this programme is to exclude, eradicate, reduce or contain pests to protect natural biodiversity at specified sites.
Species included under the Site-led Programme
|Common name||Scientific name||GNR|
|Feral goat³||Capra aegagrus hircus|
³ Feral goat means any goat that is located within the Containment Area shown in Map 14 in Appendix 4 that is not effectively constrained.
Declared Pests for Canterbury
Being a declared pest means there are specific rules that need to be met within the Canterbury region for that declared pest.
Bennett's Wallabies occupy a variety of habitats in the hill country of South Canterbury, from forested gullies, matagouri scrub and exotic forests, to tall tussock grasslands. At present, wallabies usually occur at low and moderate densities with some localised areas of high densities.
Wallabies occupy about 300,000 hectares of land in South Canterbury, centred in the Hunter Hills, but including the Two Thumb Range, the Kirkleston and the Grampian mountains. Populations also occur in Kakahu Forest near Geraldine and Pioneer Park south-east of Fairlie. There have been occasional sightings of isolated wallabies outside South Canterbury, for example on the Banks Peninsula and at Mt Oxford. Such sightings suggest that the illegal release of wallabies may be occurring.
Report wallaby sightings
At high densities (Level 4 and greater on the Guilford Scale - Appendix 6), wallabies can have significant adverse environmental effects. These include the prevention of regeneration of native bush and depleting forest understories. Wallabies also damage tall tussock grasslands, including the inter-tussock vegetation that can become depleted with a consequent increase in bare ground and increased risk of soil erosion.
They also impact on farming by eating pasture and crops, resulting in a loss of food available for livestock. Wallabies also damage exotic forests, particularly at the establishment stage, with damage being more serious in areas bordering native bush or scrub areas.
Only two toxins are registered for use for wallaby control. The most cost-effective and efficient tool for controlling wallaby to date is 1080 pellets, either aerially or hand applied.
Encapsulated cyanide, Feratox (wallaby strength not possum), is the other registered toxin. This is a ground-based control tool for use in stations or bait bags.
Both toxins require a ‘Controlled Substance Licence’ (CSL) for purchase and use. Best practice guidelines including pre-feeding, bait placement and tailored feed rates are required to ensure the best results are obtained and poison shyness is avoided.
Some people believe that the use of 1080 poison is undesirable for health and environmental reasons. Consequently, there is a continuing need to investigate, develop and implement new control tools – potentially biological agents – so that the reliance on poisons is lessened or eliminated. Shooting from a helicopter, particularly following heavy snow, can also be an effective method, but is limited to more open, tall tussock areas.
Reliance on any one method, or a method not tailored to the level of wallaby infestation, can lead to reduced kills and “educated” shy wallaby populations. For higher wallaby levels, it is best practice to pre-feed and poison, then to use shooting as follow-up control.
Recreational shooting may be useful in localised areas, subsequent to more effective control operations or when wallaby numbers are at low levels. Recreational shooting should not be used to target high levels as this creates issues of wallaby spread and shyness.
Report wallaby sightings
Containment area in Canterbury
The Containment area is from the Rangitata River to the Waitaki River, inland to the Tekapo River.
Read our Wallaby Information Sheet (PDF 529 kB) for more information on what to look for.
That no breeding populations of Bennett’s wallabies establish outside of the containment area. Ensure land occupiers in the containment area keep Bennett's wallabies numbers on their land at, or below, Level 3 on the Guilford Scale.
This scale assesses wallaby population levels.
- No faecal or track sign is seen but area known to be within feral range of wallabies.
- Infrequent faecal sign is seen. Track sign absent. One or two pellet groups when traversing 100 m. Unlikely to see any wallabies.
- Frequent faecal and track sign seen, but only in isolated pockets. Likely to see some wallabies.
- Faecal and track sign very obvious and consistent. Tracks well used. High probability of seeing wallabies.
- High densities of faecal and track sign distributed almost uniformly. Tracks well used. High probability of seeing wallabies.
Currently, there are small feral populations of goats (Capra hircus) scattered throughout the Canterbury region. Goats are social animals, they disperse slowly, and do not voluntarily cross large rivers. This results in patchy distribution and allows land occupiers to consider local eradication. They do however have high birth rates when in good condition and goat populations colonising in areas or recovering from control may roughly double every two years. The major cause of mortality is hunting, although feral pigs may prey on kids. Goats are browsing generalists and feed on woody species in forests.
Feral goats impact on indigenous ecosystems through their concentrated browsing and trampling.
Even in low numbers, their impacts on forest and scrublands can be serious – they destabilise forest ecosystems, and defoliate and eat the stems of palatable understorey species, bark saplings, and prevent regeneration of seedlings. Unpalatable shrubs increase, and on some islands, forest ecosystems have been converted to grassland.
In Canterbury, plant species most likely to be eaten include; mahoe, broadleaf, supplejack, pate, small leafed coprosma species, Asplenium bulbiferum, blackberry, and gorse. Vegetation has been seriously depleted on many of the sites occupied by goats on the Banks Peninsula, on the foothills of the Seaward Kaikouras, and in South Canterbury Department of Conservation reserves.
Goats may also affect native vertebrate and invertebrate populations by competing for food and by modifying forest habitats. Feral goats have few economic impacts, although they may occasionally compete with sheep for feed, and they have a wide range of parasites and diseases in common with sheep. Their range is limited, however, and they are controlled relatively easily, so it is not considered that they have any significant economic impact.
Goats can be controlled by shooting/hunting.
Feral Goats are listed as a pest in Canterbury’s Regional Pest Management Plan 2018–2038 as a site-led pest for the Banks Peninsula. For other locations in Canterbury, they are an ‘Organism of Interest.
Reduce feral goat numbers by at least 50% by 2038 within the Banks Peninsula containment area. It is worth noting that untagged goats are considered feral goats.
- Feral Goats - What you need to know (PDF File, 722.9KB)
- Goat Fencing Specifications - (PDF File, 42.52KB)
Rabbits occur in many parts of the Canterbury region. Their preferred habitat is grassland below an altitude of about 1000 metres, with free draining soils, sunshine, and less than 1000 millimetres annual rainfall.
Their distribution and population density are reflected by a propensity of land to harbour populations of rabbits and the potential rate of population increase.
Much of Canterbury is low-lying with rabbits being present at low densities. In these areas, night-count levels are commonly below 10 rabbits per kilometre and rabbit densities are at 3, or below, on the Modified McLean Scale.
Higher numbers of rabbits are more likely to be found on high and extremely rabbit-prone land, especially in the absence of control.
Land use can also influence the occurrence of rabbits. For example, the change from tall tussock to short tussock or improved pastures has created an environment more suited to rabbits.
Forestry, on the other hand, creates unsuitable habitat for rabbits once canopy closure is achieved, although forest margins and firebreaks can be problem areas.
The introduction of Rabbit Haemorrhagic Disease (RHD) has had a dramatic effect on rabbit populations, particularly in the highly prone areas of the Waitaki and Mackenzie.
In these two areas, rabbit levels are being maintained at very low levels, typically less than two rabbits per night-count kilometre. In most instances, the virus is capable of maintaining rabbit levels below Level 3 provided immunity levels do not develop.
In areas of high and extremely rabbit-prone land, population increase is not curbed by natural mechanisms and can quickly build to high levels. These areas occur largely in the Upper Waitaki Valley, Mackenzie Basin and the inland Kaikōura area.
Moderately rabbit-prone land is an intermediate case, although in some situations rabbits can increase to high numbers. These lands occur mainly in the free-draining hill soil areas of North Canterbury and the foothills.
Rabbits can cause a number of adverse effects. At high numbers, the control costs can be prohibitively expensive. Their impact reduces available grazing for domestic stock and subsequently decreases the financial returns to landowners and their ability to fund control.
High rabbit numbers also assist in maintaining high predator numbers. This can lead to significant costs being incurred in situations where predators carry bovine tuberculosis. On highly rabbit-prone land, and to a lesser extent on moderately prone land, rabbits, often in conjunction with other grazing animals, cause a number of environmental effects, including:
- The depletion of many plant communities and species diversity;
- An increase in areas of bare ground as well as physical disturbance of the soil, both of which increase the risk of erosion;
- A reduction in soil organic matter through overgrazing, which, in turn, results in deterioration in the physical and nutrient properties of the soil; and
- Adverse effects on indigenous and other fauna, when rabbit predators target alternative prey.
Environment Canterbury received approval to import and release the Rabbit Haemorrhagic Disease (RHD) strain, RHDV1 K5. The major nationwide release took place in March and April 2018. RHDV1 K5 is not a new virus. It is a Korean strain of the existing RHDV1 virus already widespread in New Zealand and only affects the European rabbit. RHDV1 K5 was selected for release because it can better overcome the protective effects of the benign calicivirus (RCA-A1), which occurs naturally in wild rabbit populations in New Zealand.
A vaccine (Cylap) is available in New Zealand which has been helping to protect rabbits from the current RHDV1 for many years. Studies undertaken by the Australian government indicate that this vaccine will help protect pet rabbits against the RHDV1 K5 strain.
For detailed information on control methods, implementation and monitoring for feral rabbits read ‘Best Practice rabbit control’.
Timing is important for poisoning. March to August immediately prior to breeding is the optimum time for poisoning. From August to February, it is difficult to poison due to territorial behaviours during breeding and an abundance of natural food. Bait shyness can be avoided when correct practices are used. Control history is relevant. If previous control has been unsuccessful, shyness may be developing.
Shooting can be done throughout the year as required. For night shooting to be effective at least 70% of the area needs to be accessible.
Fumigation does not require the rabbit to eat bait so is effective in areas where bait shyness is a problem. It is labour intensive but is effective when used in the breeding season to control young rabbits that do not move from the burrow. Phosphine is most commonly used.
Repellents and tree protectors
Several commercial repellents are available. Most repellents will need to be applied periodically as effectiveness reduces. For a repellent recipe visit the National Pest Control Agency website.
Effective fencing will slow the recovery of rabbit populations after control, or allow localised eradication to protect a high value resource. For details on appropriate fencing materials visit the National Pest Control Agency website.
In some situations, you may be able to make areas less suitable for rabbits to live. This is called habitat manipulation. It is useful for the home garden environment.
Keep your property clear of stacked woodpiles or rubbish in garden areas. Fix small entry gaps under buildings and sheds to prevent them from gaining access. Under prune shrubs and hedges to reduce vegetation that offers rabbits protection from the elements and predators. Maximising lawn areas makes your garden less desirable if there is not much protective cover nearby.
It is an offence to cause unnecessary suffering of animals caught in traps. Trapping is a useful technique for urban areas where other methods such as shooting or poisoning are not suitable.
A live trap is best to reduce the likelihood of killing a domestic animal. The rabbit will need to be killed humanely once captured as releasing it to another location is a biosecurity offence. A professional pest control operator experienced with trapping may be a good option if you are not able to kill the animal humanely yourself.
To reduce the negative effects of feral rabbits on production and environmental values in Canterbury.
This goal is for all Canterbury land occupiers to maintain feral rabbit population levels at or under Level 3 on the Modified McLean Scale.
As a Canterbury land occupier, you are responsible for feral rabbit control on your land. You need to keep feral rabbit populations at level 3 or lower on the modified McLean Scale on your land. (see scale below).
Environment Canterbury is responsible for monitoring feral rabbit populations within Canterbury. If we identify a land occupier is not meeting their obligation to achieve feral rabbit populations at level 3 or below on the modified McLean Scale we will discuss their options and the actions they can take to achieve this goal for their property.
We have an enforcement process available to us when it’s necessary to ensure that a land occupier meets their obligation to control rabbits. It is important to the Canterbury community that neighbours are not negatively impacted by another’s inaction for rabbit control.
Modified McLean Scale
|1.||No sign found. No rabbits were seen.|
|2.||Very infrequent, sign present. Unlikely to see rabbits|
|3.||Pellet heaps spaced 10m or more apart on average. Odd rabbits are seen; sign and some pellet heaps showing up.|
|4.||Pellet heaps spaced between 5m and 10m apart on average. Pockets of rabbits; sign and fresh burrows very noticeable.|
|5.||Pellet heaps spaced 5, or less apart on average. Infestation spreading out from heavy pockets.|
|6.||Sign very frequent with 2–3 pellet heaps often less than 5m apart over the whole area. Rabbits may be seen in large numbers over the whole area.|
|7.||Sign very frequent with 2–3 pellets heaps often less than 5m apart over the whole area. Rabbits may be seen in large numbers over the whole area.|
|8.||Sign very frequent with 3 or more pellet heaps often less than 5m apart over the whole area. Rabbits likely to be seen in large numbers over the whole area.|
Table: Modified McLean Scale credit: National Pest Control Agencies (NPCA).
For more detailed information on feral rabbits in Canterbury, read pages 50–52 of the Canterbury Regional Pest Management Plan 2018–2038.
Koi carp are an ornamental strain of the common carp (Cyprinus carpio) native to Asia and Europe. It is believed they came into New Zealand accidentally with goldfish in the 1960s.
If you think you have found Koi carp in Canterbury waters, please contact Environment Canterbury on 0800 324 636 so we can arrange control.
Koi carp is a declared pest in the Canterbury Regional Pest Management Plan 2018–2038, managed in the Exclusion Programme.
To prevent Koi carp from establishing in Canterbury
No one may sell, propagate or distribute Koi carp in Canterbury or New Zealand.
Possums (Trichosurus vulpecula) are present throughout the region, with numbers depending on the availability of suitable habitat. Throughout the mixed cropping areas of the plains and downlands and in most beech forests, their numbers are generally very low and scattered (less than one per hectare). In dry scrublands in South Canterbury and in inland native and exotic forests in North Canterbury, their numbers are generally light to medium (one to two per hectare). In forested areas of Banks Peninsula and coastal North Canterbury, their numbers are generally medium to high (two to six per hectare).
Possums begin breeding at one to two years of age, and populations can increase at a rate of 22–30% per year, indicating that a population at 20% of its carrying capacity is capable of recovering to its full carrying capacity within ten years. Juvenile possums disperse an average of six kilometres from their home but can move up to 30 kilometres per year.
Possums are one of the most serious threats to biodiversity values. Possums are primarily herbivores and feed on a variety of leaves, flower buds, fruit, ferns, and fungi. They feed also on invertebrates and opportunistically on the eggs and nestlings of birds. As a result, a very large range of both indigenous and introduced flora and fauna are affected. Despite this wide range, possums are strongly selective browsers and the majority of their diet in any one location consists of only a few species. The species most common in a habitat are not necessarily those most frequently eaten. Therefore, extensive defoliation of favoured plant species and progressive change in forest composition to less favoured species occurs.
Possum damage, is, however, not uniform across habitats. Possum damage appears to be variable within and between plant populations, communities and ecosystems, and is influenced by a range of biotic and abiotic (living and non-living) factors. These factors may predispose plant communities to possum damage, trigger damage episodes, or accelerate the rate of vegetation change.
Within forest communities, possum browsing is frequently concentrated on a few trees that may be defoliated or killed, while neighbouring trees may be unaffected. At a regional scale, plant species such as mistletoe or fuchsia can coexist with long-established possum populations, while other populations of the same species can be threatened with extinction.
Possums can also impact on native animals by predation of insect species, snails, and birds.
Possums cause economic effects by damaging exotic forests, eating pasture, and through the spread of bovine tuberculosis. Clover and pasture grasses were a major component of possum diet in a study of possum feeding on Banks Peninsula. However, the possum browsing on pasture is likely to be a minor problem apart from pasture/bush margins and is likely to be accommodated within the normal biological response rates of those systems. It may be more significant in areas, such as parts of Banks Peninsula, where the bush/pasture interface is a major feature. The damage to exotic forests also tends to be limited.
Bovine tuberculosis is the major economic impact associated with possums. There is evidence to support the link between possums and tuberculosis in farmed animals. Recent studies show that cattle and deer may lick and nuzzle tuberculosis infected possums in the terminal stages of the disease as the possums wander around open ground in daylight. Sheep do not appear to exhibit this level of curiosity, and to date have remained relatively free of the disease.
Possums are subject to management under a National Pest Management Strategy (NPMS) for bovine tuberculosis by way of feral vector control programmes. The NPMS programme is managed by the Animal Health Board (Trading as TBFree). The objective is to control bovine tuberculosis in cattle and deer. The strategy also specifies possums and other suspected carriers (e.g. ferrets) of bovine tuberculosis to be pest agents.
Possums are declared pests in Canterbury’s Regional Pest Management Plan 2018–2038 and are managed as a Site-Led Programme.
For the site in the map(s) above, the number of possums will be reduced to 5% Residual Trap Catch.
Environment Canterbury will take a lead role in bringing about the desired levels of environmental protection by working in collaboration with land occupiers and other agencies where appropriate.
Rooks belong to the family Corvidae which includes intelligent birds like crows and jays. Their natural breeding range is Europe and Asia, eastern Siberia and Mongolia. Many migrate south to winter around the Mediterranean, in Iran and the northern part of the Indian sub-continent.
Rooks are gregarious, not only when feeding together but also breeding and roosting together. These roosts are known as rookeries. They often use the same sites as in previous years and are mostly found in large pines or eucalyptus trees.
The males will forage for food in communal feeding grounds several times a day until the young can fend for themselves at three months old. During the winter months, birds from many rookeries will congregate in winter roosts which may contain up to several hundred birds.
In 1971 Rooks were declared an agricultural pest in the Hawke’s Bay. It is thought around half the population was shot (approx 35,000). Because of shooting, rooks displaced and spread more rapidly and established colonies near Miranda, Tolaga Bay near Gisborne, southern Waikato, and Northland.
In New Zealand the breeding season is August–January. Rooks tend to build their nests in the tops of very tall trees such as poplars and pines in late August. Large rookeries may contain several hundred nests. Nests are large, untidy and made of twigs, leaves, mud and lined with grass. The female incubates the eggs and is fed by the male while brooding. The eggs are bluish green, blotched with brown.
During winter, birds from several breeding rookeries will travel up to 20 kilometres each night to roost together at a large or long-established rookery, called “parishes”. In the morning they disperse to feeding grounds around their own rookeries.
Some people do not consider Rooks to be a pest as they assist in control of insect pests such as army worms and grass grubs, however when the population is allowed to reach significant numbers they can cause extensive damage to crops as their other food supply falls. Damage to crops and pasture usually only occurs where established rook populations exist and not the occasional bird, however, rook populations do increase very quickly if they nest.
Rooks show a strong preference for foraging in fields of cereals at all stages of the crop, in recently cultivated land, and in stands of walnut trees. Feeding ranges are influenced by the occurrence of highly preferred foods, with extensive flights being made to walnut trees and to recently tilled fields. The effect of large flocks of rooks is to severely damage or destroy newly emerging crops or pasture.
Historically, rooks ranged the Canterbury Plains between the Waimakariri River and the Rangitata River. In 1994, there were 1642 birds, with the largest population occurring on Banks Peninsula. Since then, small populations have been found in Kaikōura and Waikari.
Environment Canterbury organises rook control, which is a specialised task. The birds are intelligent and unsuccessful control can lead to rooks becoming wary and much more difficult to control. Rookeries can fragment and new rookeries establish.
For this reason, land occupiers are asked not to control them but to inform Environment Canterbury of their presence or any sightings. Control usually takes place in spring around the rookeries, when young birds are demanding large amounts of food from adults.
Successful control has been achieved to date through a co-ordinated approach involving the use of restricted poisons such as 3-chloro-p-toluidine hydrochloride (DRC 1339) as well as favourable weather conditions, and limited food sources. These conditions may not occur every year, hence effective control cannot be guaranteed every year.
Contact Environment Canterbury on 0800 324 636 or firstname.lastname@example.org if you suspect you have seen a rook(s). Please do not attempt to shoot or otherwise disturb the birds. Environment Canterbury staff will inspect and arrange control.
Rooks are listed as pests in Canterbury’s Regional Pest Management Plan 2018–2038 in the Eradication Programme.
To reduce the Canterbury Rook population to zero density by 2038.
Environment Canterbury is responsible for inspection and organising the control of rooks.
Those species listed in the Canterbury RPMP under this category are not declared as pests. We are monitoring these ‘organisms of interest’ to gain a picture of their presence and distribution in the region. Monitoring these species will support informed decision-making about future pest management.
It is important to note that some of the species in Canterbury’s 'organisms of interest' list may have an ‘unwanted organism status’, which can be checked on Ministry for Primary Industry’s unwanted organism register. A species that has an unwanted organism status means that you are not allowed to sell, propagate, transport or communicate that species within New Zealand.
There is room within Canterbury’s Regional Pest Management Plan to consider other ‘unwanted organisms’ not already on the ‘other organisms of interest’ list as candidates to control under future site-led programmes.
Red deer are selective feeders, with about 80 per cent of their feed obtained by browsing and the remainder through grazing. They have strong food preferences and favour Pseudopanax species (lancewoods), Coprosma species, pate, broadleaf, and the fern Asplenium bulbiferum. In most forests, these are now severely depleted and deer switch to less palatable species. They even eat relatively unpalatable beech, podocarps and woody shrubs when more palatable shrubs have been eliminated. Deer have considerably altered many forests, and the preferred browsing species are now rare. Fallow deer are thought to have severe impacts in beech forests, although the impacts are not as well studied because fallow deer are less common.
Deer affect the sustainability of the native forest ecosystems by modifying their structure and composition.
Local reductions of 50–60 per cent in stem frequency and 30 per cent in woody species have been recorded, and they eliminate the understorey, prevent or delay regeneration, and alter botanical biodiversity toward unpalatable species. Many vulnerable species will only regenerate in the near absence of feral deer, and their browsing is presumed to lead to the loss of species diversity. Feral deer populations are sustained in depleted forests by leaves falling from the canopy above, and their populations may remain at levels that are able to continue driving declining patterns of forest diversity.
Red deer may compete with native bird life, and the decline of kokako in the North Island has been attributed in part to the degraded habitat caused by deer and possums. Their effect on South Island bird populations is uncertain, but it is possible they are similarly affecting native pigeon populations.
Grazing pasture forms only a small part of feral deer feeding. As their numbers are low and confined to less productive pasture types, their economic impact is not likely to be significant.
Feral pigs may affect the viability of threatened species and affect native ecosystems and biodiversity directly by eating plants and animals. Indirect threats arise from soil disturbance while rooting for food or by competing for food with native animals. In some favoured sites pigs can root up most of the ground surface. While this may encourage the regeneration of beech species particularly, constant disturbance negates this. Predation on lambs and damage to pasture, while once a significant effect, is now isolated and largely dealt with by land occupiers.
Pigs can also contract and spread bovine tuberculosis through scavenging infected carcasses. They can maintain the disease over long periods without undue health problems, therefore they can be a problem if they are released into bovine tuberculosis free areas.
Recreational hunting provides some control on feral pig numbers. Feral pigs can be stalked and shot with a rifle, but are more often hunted with specially trained dogs. More information on the ecology, history and management of pigs in New Zealand can be found on the Global Invasive Species database.
Ferrets are common throughout Canterbury in pasture, scrublands and braided riverbeds. Their distribution generally matches that of rabbits in pasture and semi-improved grassland. Their population responds to changes in the rabbit density and can range from 2.8 to 8.4 per square kilometre in tussock grassland. Stoats and weasels are slightly smaller than ferrets, and are widely distributed but more common in forested areas. Their numbers are lower in pasture and tussock grasslands but can range between 2.2 and 70 per square kilometre in beech forest, and their population dynamics are linked to fluctuations in their primary prey – birds and small mammals in forested areas. Both stoat and ferret populations have the potential to increase rapidly and reinvade areas following control or changes in their prey density. Ferrets rely heavily on rabbits as their primary prey species, but they also feed on a variety of indigenous wildlife as secondary prey. Large-scale changes in rabbit numbers, such as following control operations, can cause substantial changes in ferret diets.
Stoats are specialised predators of small mammals and birds, although they do predate on rabbits in riverbeds and tussock grassland. In forested areas, their numbers fluctuate in response to beech seeding years.
Weasels are found occasionally in Canterbury. Because of their patchy distribution and scarcity, their impacts on biodiversity, soil and water quality and indigenous species are largely unknown compared with either ferrets or stoats. However, where they are present it is considered they do pose a threat to indigenous wildlife. They are not discussed further in this strategy.
Ferrets and stoats can have a serious impact on native fauna through direct predation. Ferrets and stoats have been known to prey on brown kiwi, weka, white-flippered penguin and pigeons in the forest/scrub/pasture mosaic. Ferret predation is the main cause of death for black stilts. Other vulnerable riverbed species include the wrybill, black-fronted tern and Caspian terns.
Ferrets also pose a threat to several species of skinks and geckos as well as the native invertebrates, such as giant wetas and grasshoppers. Stoats are considered a serious conservation pest because they threaten the long-term viability of several species of birds through predation, and in Canterbury populations of yellowhead appear particularly vulnerable. It is now well documented that ferrets can carry bovine tuberculosis and general agreement amongst the scientific community that they play a role in its transmission to cattle and deer. They are considered a major vector of bovine tuberculosis in Canterbury.
Anecdotal evidence supports feral cats causing similar effects to those of mustelids.
Hedgehogs negatively impact New Zealand’s ecology as they eat the eggs and chicks of our native ground-dwelling birds and consume large numbers of native invertebrates.
They are proven predators of the eggs of riverbed breeding birds, such as banded dotterel and black-fronted tern, and have been known to kill and eat chicks of a variety of species, up to the size of two week old chickens. Small ground-nesting species such as pipit may be particularly vulnerable. Hedgehogs have been shown to be serious predators of colonial nesting sea birds in Britain. Hedgehogs are a major predator of northern populations of New Zealand dotterel.
Hedgehogs may also have significant impacts on native slug, snail, and terrestrial insect populations. They have a voracious appetite for invertebrates on Quail Island and take many local endemic species. They are known to eat the rare giant native centipede and rare insects in the MacKenzie Basin. They have been known to eat the native snail Wainui aurnula. Lowland populations of Powelliphanta snails may also be severely affected, particularly the Patarau and Otaki sub-species. Only smaller (juvenile) snails are eaten but this severely affects recruitment and population recovery.
Hedgehogs are likely to prey on lizards, particularly in cooler periods when lizard activity slows. Hedgehogs may also be predators of native frog species, as they are known to take introduced frogs and their range overlaps with some endemic frog species.
Hedgehogs are a spill-over host for bovine tuberculosis but are not thought to transmit the disease. Hedgehogs often have lots of fleas, although the specific hedgehog flea didn’t make it to New Zealand. They can carry hedgehog ringworm, but rarely transmit it to humans. Hedgehogs suffer from hedgehog mange mite, which buries its eggs in the skin, creating scaly skin and scabs all over the body. The parasite blinds the hedgehog (so you often see these ones during the day) and kills large numbers of hedgehogs.
Magpies are particularly aggressive during the nesting season which begins in June/July and may run through to January. It is around this time that magpies display territorial behaviour as they patrol up to five hectares, bombarding people and other birds. When humans enter magpie territories they may continuously bomb and swoop while emitting a clicking sound from their beak as an additional warning.
This behaviour generally does not physically harm the intended victim but is used to scare them away. If you get in this situation or are nervous about having to walk through a magpie area, it pays to hold an object above your head (e.g., a tall stick) as they tend to swoop for the highest point.
For magpie control, contact: Excell pest control: (03) 325 1103
The most widely used poison for magpie control is Alphachloralose.
Alphachloralose is a narcotic that effectively anaesthetises birds when consumed. Winter and early spring is the best time to incorporate Alphachloralose into magpie control as the birds are more likely to accept offered food when weather is cooler.
For best poisoning results, pre-feed the birds without the bait so they become familiar with both the food source and locality and become less suspicious.
- Pre-feed magpies with small chunks of bread. Lay in open, ungrazed areas where the Magpies have been observed frequenting. Pre-feeding should last for 3–10 days or to the stage where magpies are settling into the routine of readily accepting offered bread.
NOTE: Setting bait in the open should discourage non-target native birds from feeding, as natives are generally less comfortable with foraging in open areas. Scattering small pieces of rolled tinfoil in the vicinity can help attract magpies directly to the bait.
- Keep to a fixed routine when pre-feeding. Try to put bait out at the same time everyday and approach/depart baited area via the same route.
- Note how much bait is being consumed so you are able to assess the approximate amount to be offered when poisoning.
- Cut the quantity of pre-feed baits by half the day before you poison with Alphachloralose. There should be less Alphachloralose treated bait made available than non-toxic bait used during pre-feeding.
NOTE: Try to poison during a day where weather is forecast to be cool, to reduce the likelihood of non-target birds taking bait.
- Add Alphachloralose paste to the bread following the manufactures instructions.
NOTE: One piece of Alphachloralose laced bread is approximately enough to comatose one magpie; however, scatter a few extra pieces to ensure there is enough for each bird.
- Once Alphachloralose bait is laid, observe baited area from a hidden position. Note the directions magpies leave the bait site.
- Following the departure of the last magpie (or after first sign of birds displaying narcotic symptoms), scour areas in the approximate direction(s) the magpies flew to and gather up the comatose birds in a sack at 30 minute to 1-hour intervals.
- Dispose of magpies humanely by placing in freezer, breaking neck or cutting head off with an axe.
- Bury or burn the dead birds to prevent secondary poisoning in other animals that may consume carcasses.
- Collect all uneaten bait and dispose of it.
- Following the collection of baits, check the treated area approximately 45 minutes-1 hour afterwards to ensure all magpies have been collected.
NOTE: If non-target birds have accidentally come into contact with baits you can revive them by placing in a warm area to prevent death from hypothermia that will occur if left outside in a cool environment.
Although Alphachloralose used for bird control is not highly toxic ALWAYS read and follow the manufactures warning & guide label prior use.
Permitted in rural areas only
Shooting is not recommended for eradicating a large number of birds as you may eliminate a few birds but make the rest of the population suspicious/wary of further attempts.
Suitable weapons include shotgun or at greater distances any rifle from .22 to a .223 is appropriate. ALWAYS consider your firing zone when using rifles and shotguns.
Birds can be shot as you see them or alternatively the use of a magpie's distress call can be incorporated. The use of magpie and predatory bird decoys around the hidden music player can add realism and provide a specific target area for magpies to investigate. Using this method is useful as it allows the shooter the opportunity to find /create a concealed site with a clear view of the decoys/target area.
Leave shot birds as a further attractant.
The Larsen Trap is the most popular trap for capturing magpies. A Larsen trap is generally made up of 3 or more separate compartments. One compartment is reserved for a ‘bait’ bird known as a call bird or ‘Judas’. All compartments possess their own external door set open. Doors are sprung shut when a magpie sits or disturbs a perch used to hold open the compartment door, trapping the magpie inside. Call birds are initially caught and lodged in a central compartment of the trap.
To capture a call bird
- Position the Larsen trap in an open area known for magpies and is unlikely to be disturbed.
- Scatter bread around the entranceways to the trap
- Bait the actual compartments with a piece of meat, fat or dog roll and potentially a mirror or rolled up pieces of tinfoil to act as an additional attractant.
- Once a call bird is caught, carefully extract it from the compartment and place in central section of the trap.
- Reset external entrances and wait for other magpies to be caught as the call bird acts as an attractant. Bait may also still be required to further entice other magpies.
- Check traps daily; on dark if possible, so other target birds don’t grow suspicious. It is illegal to hold a live animal in a trap for more then 24 hours.
- To extract caught magpies (thick gloves recommend), open compartment and handle the bird around the back/neck region. Kill magpies by either breaking neck or cutting the head off with a small axe or machete.
Note:: Call birds should be looked after well with an ample supply of water, food (dog roll ideal), a fixed perch and shelter from the elements (often Larsen Traps have a wooden compartment for this reason). Replace call birds reasonably regularly as they tend to become tame and their distress vocalization ceases/lessens.
Stoats occur in many parts of the Canterbury region. Their preferred habitat is grassland below an altitude of about 1000 metres, with free draining soils, sunshine, and less than 1000 millimetres annual rainfall. Their distribution and population density are reflected by a propensity of land to harbour populations of rabbits and the potential rate of population increase.
Ferrets and stoats are capable of having a serious impact on native fauna through direct predation. Ferrets and stoats prey on brown kiwi, weka, white-flippered penguin and pigeons in the forest/scrub/pasture mosaic.
Ferret predation is the main cause of death for black stilts. Other vulnerable riverbed species include the wrybill, black-fronted tern and caspian terns. Ferrets also pose a threat to several species of skinks and geckos as well as native invertebrates such as giant wetas and grasshoppers. Ferrets are considered a major vector of bovine tuberculosis in Canterbury because they carry bovine tuberculosis and play a role in its transmission to cattle and deer.
Stoats are considered a serious conservation pest because they threaten the long-term viability of several species of birds through predation, and in Canterbury, yellowhead populations appear particularly vulnerable.
Anecdotal evidence supports feral cats causing similar effects to those of mustelids.
Because ferret and stoat populations can recover quickly, increasing the frequency of control is likely to have more of an impact on numbers than doing a single annual trapping operation.
Trapping has a short-term effect.
Weasels are occasionally found in Canterbury. Because of their scarcity and patchy distribution, their impacts on biodiversity, soil and water quality and indigenous species are largely unknown compared with ferrets and stoats. However, where they are present it is considered they do pose a threat to indigenous wildlife.
Ferrets, stoats and weasels are capable of having a serious impact on native fauna through direct predation. Ferrets, stoats and weasels prey on brown kiwi, weka, white-flippered penguin and pigeons in the forest/scrub/pasture mosaic.
Weasels predation is the main cause of death for black stilts. Other vulnerable riverbed species include the wrybill, black-fronted tern and caspian terns. Weasels also pose a threat to several species of skinks and geckos as well as native invertebrates such as giant wetas and grasshoppers. Weasels are considered a major vector of bovine tuberculosis in Canterbury because they carry bovine tuberculosis and play a role in its transmission to cattle and deer.
Weasels are considered a serious conservation pest because they threaten the long-term viability of several species of birds through predation, and in Canterbury, yellowhead populations appear particularly vulnerable.
Anecdotal evidence supports feral cats causing similar effects to those of mustelids.
Because populations can recover quickly, increasing the frequency of control is likely to have more of an impact on numbers than doing a single annual trapping operation.
Trapping has a short-term effect.
Three species of introduced social wasps are present in Canterbury, although only two of these, the German wasp (Vespula germanica) and the common wasp (Vespula vulgaris) are established. The German wasp has been established since 1954 in the region, but the common wasp is a more recent arrival and it now appears to be the dominant species in the region. The common wasp has displaced the German wasp from beech forests containing honeydew although the two species appear to co-exist elsewhere.
When the common wasp was spreading in Canterbury in the late 1980s and early 1990s very high densities of the species were recorded, but since that time populations have fluctuated at lower levels. Wasps however still occur at high levels, particularly in beech forest.
Wasps feed on carbohydrates such as nectar, honeydew, ripe fruit juice, and honey from beehives to meet energy requirements.
Protein sources are required to feed developing larvae and include live invertebrates and flesh scavenged from dead animals.
Honeydew is readily available, and the number of nests can range between 10 and 36 per hectare depending on the season in beech forest.
Their numbers are typically lower in pasture, scrub, hardwood forests, and in beech forests in areas where the rainfall is high enough to wash the honeydew off the trees.
As well as having effects on biodiversity, wasps also have an effect on human activities. Wasps affect public health as their sting produces localised swelling and itching in most people, but are capable of causing a systemic hypersensitivity reaction in 3.3 % of the population. This swelling can range from large local swelling to swelling of the airways and anaphylaxis.
Deaths from wasp stings are rare – approximately two people die every three years from wasp or bee stings. Medical attention is more common, but it is not possible to attribute a specific number of hospitalisations or general practitioner visits to wasp stings. Wasps may also pose a public health hazard through transmission of disease organisms, although again this is rare.
Wasps are a significant source of damage to amenity values. Department of Conservation offices in Hanmer Springs, Mt Thomas, and Arthur’s Pass (Craigieburn and Mt White areas) all report disruption of recreational users of conservation areas by wasps. Landcare Research at Lincoln receives over 1700 calls annually regarding wasp nests in and around Christchurch.
The impact of wasps on economic wellbeing arises through their impacts on the beekeeping industry. Wasps compete with honeybees for food sources, and rob hives and honey processing facilities. In beech forest, wasps have reduced honeydew abundance to the extent that bees do not feed on it for three to four months of the year.
There are potentially some losses associated with fruit production, although these are more likely from disruption than direct damage. Other economic impacts may include the occasional stock death, possible deterrence of possum feeding at bait stations, and the impact on the tourism industry of high wasp numbers at scenic locations.