Feral Mammal Control

Policy

The NZVA considers that the welfare of pest mammals must be given serious consideration when methods of killing them are selected.  The methods chosen must result in death as quickly as possible with a minimum of pain and distress. 

Explanation

Feral mammals considered pests include any land mammals living in a wild state if they compete with domestic or native animals for food, if they might transmit diseases to humans or animals, or if they damage or kill crops, pasture or native animals

It is reasonable to assume that pest mammals are capable of experiencing as much pain and suffering as their domestic counterparts. As veterinarians we have an obligation to ensure humane treatment of all animals, whether they are classified as “pests” or not, so methods used for destruction must be as humane as practical. They must also be as specific as possible for the pest species targeted, minimising the risk of inadvertent killing of other species and minimising damaging effects on the environment.

The NZVA also recognises that the relationship between pest mammals, other animals and the environment is complex, requiring that any pest control system should be integrated into total land management programmes that address issues such as overgrazing, erosion, land rehabilitation, prey switching, and preservation of endangered fauna and flora and their natural habitats.

Guidelines

The following guidelines are for veterinarians when advising lay-people on the best methods to use to kill pest mammals when either a veterinarian is not available or it is not practical to use a veterinarian.

Various methods are available to kill pest mammals. These include use of capture traps, kill traps, poisons, shooting, hunting with dogs and biological agents. 

1. Traps

Trapping is a commonly used method of pest mammal control.  The Animal Welfare Act 1999 defines a “trap” as a net, cage, snare, pen, pitfall or mechanical thing (not being a firearm) used for the purpose of killing, entrapping, capturing, entangling, restraining or immobilising an animal.  Section 36 (1)(a) of the Act requires that each trap must be inspected within 12 hours after sunrise on each day the trap remains set. Section 36 (1)(b) requires that trapped animals be removed or cared for properly or killed without delay.

To ensure humane destruction by trapping with minimum stress, the NZVA prefers the use of approved species-specific traps that kill instantly. Kill traps should be strategically positioned and baited to target pest species. 

Live-capture traps include cage traps and leg-hold traps - of the latter, only types like the Victor Soft Catch traps are acceptable to the NZVA while those such as Lanes Ace gin traps are not acceptable because they frequently cause extensive injuries to the trapped animal.  If animals captured in live-capture traps are to be killed, they must be killed promptly and humanely.  Euthanasia by a veterinarian may be the most humane option but this is seldom practicable.  Depending on the species and the circumstances, acceptable alternatives might be shooting in the brain with a rifle by a licensed operator or a heavy blow to the head by a skilled operator so that there is a minimum of pre-slaughter handling, fear and trauma.  It is important that anyone attempting a blow to the head first receives training or guidance from an experienced operator.  Gassing using car exhaust fumes which have been cooled by being passed along a long tube (or bubbled through water) into a plastic bag containing the cage may be relatively humane.  Drowning by immersing cages in water is not acceptable.

2. Poisons

Poisons (vertebrate toxic agents) may be acceptable if they cause a minimum of pain, fear and distress.  There has been increased research recently into the relative humaneness of poisons for pest destruction. Cyanide, for example, causes death by hypoxia and has the advantage of taking effect quickly so is considered relatively humane. The NZVA has a Position Statement on use of 1080 for pest control (B4.5.1). To minimise the risk of poisoning to non-target species, appropriate baits must be used and the stations must be appropriately designed and strategically placed.  Restrictions on the use of vertebrate toxic agents should be noted.

3. Hunting with dogs

The NZVA has concerns about using dogs to hunt feral mammals.  In particular, the welfare of feral pigs is of concern. Because of their larger size, pigs can experience severe prolonged distress if mauled by dogs before they are killed, and there is also a high risk of serious injury to the dogs. To promote more humane treatment of the animals involved, hunters should be encouraged not to use holding dogs, which physically attack the pigs, but to use only “finder” and “bailer” dogs. Hunters should be encouraged to provide their dogs with protective collars and to carry a firearm suitable for killing pigs as well as a knife.

4. Biological agents

In general, the NZVA finds the induction of a disease causing death less acceptable as a means of pest control than methods that are more humane and much faster. However, rabbit haemorrhagic disease (rabbit calicivirus) has given some degree of control of rabbit numbers in certain areas, although increasing immunity to the disease may reduce its effectiveness over time.

The NZVA is opposed to the introduction of the myxomatosis virus for the control of pest rabbits because of the degree of suffering it induces prior to death.

5. Fencing

The NZVA applauds the use of excluder fencing to protect vulnerable areas, while acknowledging that the cost of such fencing prevents its use on a widespread basis.

6. Stray and Feral Cats

While recognising the importance of cats as a companion animal in New Zealand society, the NZVA is aware that this species can pose a considerable danger to wildlife, including native and endangered species. Members are referred to The NZVA Policy on Responsible Cat Ownership, particularly sections 3 and 6.

Policy Files: 

13a - Feral Mammal Control - 20Jan06.pdf