Managing animal pests

Environmental effects

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.

Economic effects

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

Wallabies sighted outside of the containment area should be reported to Environment Canterbury - Biosecurity Timaru 03 687 7800 or toll-free on 0800 324 636 or through our online app.

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.

Related documents

• Bennett’s Wallabies - What you need to know (PDF File, 402.65KB)

Bennett’s Wallabies are listed as a pest in Canterbury’s Regional Pest Management Plan 2018–2038 in the Sustained Control programme.

Goal

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.

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.

Related documents

• Bennett’s Wallabies - What you need to know (PDF File, 402.65KB)

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.

Related Documents:

• Feral Goats - What you need to know (PDF File, 722.9KB)
• Department of Conservation - Feral goats

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.

Goal

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.

Related documents

• Feral Goats - What you need to know (PDF File, 722.9KB)
• Goat Fencing Specifications - (PDF File, 42.52KB)

 

 

 

 

 

 

 

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:

1. The depletion of many plant communities and species diversity;
2. An increase in areas of bare ground as well as physical disturbance of the soil, both of which increase the risk of erosion;
3. A reduction in soil organic matter through overgrazing, which, in turn, results in deterioration in the physical and nutrient properties of the soil; and
4. 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’.

Options include:

Poisoning

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

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

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.

Fencing

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.

Habitat Modification

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.

Trapping

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.

Related documents

• Feral Rabbits - What you need to know (PDF File, 280.83KB)

Feral rabbits are listed as a pest in Canterbury’s Regional Pest Management Plan 2018–2038 in the Sustained Control Programme.

Goal

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.

Related documents

• Feral Rabbits - What you need to know (PDF File, 280.83KB)

Koi carp cause habitat loss for plants, native fish, invertebrates and waterfowl.

They do this by the way they feed like a vacuum cleaner sucking everything up and blowing out what they don’t want. This stirs up the mud from the bottom of ponds, lakes and rivers and dislodges native aquatic plants. They are opportunistic omnivores, eating a wide range of food, including insects, fish eggs, juvenile fish of other species and a diverse range of plants and other organic matter.

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.

Goal

To prevent Koi carp from establishing in Canterbury

Responsibilities

No one may sell, propagate or distribute Koi carp in Canterbury or New Zealand.

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.

Follow best practice control of possums.

Possums are declared pests in Canterbury’s Regional Pest Management Plan 2018–2038 and are managed as a Site-Led Programme.

Goal

For the site in the map(s) above, the number of possums will be reduced to 5% Residual Trap Catch.

Responsibilities

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.

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 biosecurity@ecan.govt.nz 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.

Goal

To reduce the Canterbury Rook population to zero density by 2038.

Responsibilities

Environment Canterbury is responsible for inspection and organising the control of rooks.

Contact Environment Canterbury on 0800 324 636 or biosecurity@ecan.govt.nz if you suspect you have seen a rook(s) or rookery.

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.

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

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.

Related documents:

• Ferret Management
• Predator trapping best practice

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

Trapping has a short-term effect.

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

Trapping has a short-term effect.

Wasps have a major impact on indigenous ecosystems through competition for food sources and predation on native insects.  In native forest, up to 90 per cent of the honeydew standing crop may be reduced in the peak wasp season, affecting the feeding of kaka, bellbird, tui, and silvereye.  The prey intake of wasps in northern South Island beech forest is estimated to be similar to that of the entire insectivorous bird fauna.  The impact of this predation is both on the native invertebrate biodiversity and the native insectivorous birds with which wasps have 80-100 per cent of their identified diet in common.

Health effects 

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. 

Economic impact

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.