Animals labelled as ‘pests’

Our work Animals in Aotearoa Animals labelled as ‘pests’

Animals labelled as ‘pests’

Animals who have been introduced to New Zealand are often described as pests and endure some of the worst treatment of all animals at the hands of humans. But just like other animals, these creatures think and feel and are recognised as sentient in our law.  Rabbits, stoats, cats, deer, pigs and goats were all deliberately introduced to New Zealand, and rats and mice were incidental arrivals with new groups of humans.


Introduced species represent a huge number of individual animals, so the way we treat them matters.  


Many of these introduced species, such as cats, rats, possums and rabbits, can have rewarding relationships with humans. Others are often persecuted for simply existing in the wild. Sadly, many introduced species are commonly demonised in print and broadcast media, instead of being presented as the sentient beings they are. This demonisation fuels the public’s belief that these creatures don’t matter and makes it easier for people to commit cruel acts against them.

Where there is a conflict between animal species, often between native and introduced species, there is a range of humane options available to manage these conflicts.


Possums are fascinating creatures who get a bad rap in New Zealand. They are mostly herbivorous and feed mainly on leaves. These fascinating marsupials carry their babies in their pouch for around six months. Once the babies are old enough to leave their mother’s pouch, they ride on her back until they are ready to fend for themselves.

Possums have prehensile tails, which they use to grasp branches, and sharp claws for climbing. They are nocturnal, and have a vast range of vocalisations, which range from grunts and clicks to screeches and alarm chatters. You may have been lucky enough to hear these amazing sounds while camping in the bush.

Possums in New Zealand

The possum is undoubtedly the poster child for abused introduced species. A native in Australia, possums are protected by law in that country.

They were introduced to New Zealand in the 1800s in an attempt to create a fur trade. There is now estimated to be more than 50 million possums living in New Zealand.

Use of poisons

The use of poisons to kill introduced species is sadly commonplace in New Zealand. Most of these compounds cause prolonged deaths, the animals suffering for hours or sometimes days before dying. The poison 1080 is one of those most widely used and often causes animals to have muscle spasms and seizures for up to a day or more before death. Brodifacoum is a poison that is commonly used to kill rats. This poison makes the animal slowly bleed to death internally, which can be painful and distressing. Introduced birds like pigeons are often poisoned with alphachloralose, a poison which causes seizures and paralysis – poisoned birds often die from exposure or predation.

All poisons are indiscriminate, meaning any animal that ingests the poison may be affected.

Accidental poisoning of ‘non-target’ animals, including native species, can occur, and the poisoning of pet dogs and cats can also happen. There are also concerns about environmental contamination with poisons such as 1080.

A culture of violence

Introduced species are often demonised, and killing of these animals by members of the public is commonly presented as a positive act.

School possum hunts are annual events in some regions and reinforce this idea, as well as desensitising children to the violence involved. Sadly, terrible animal welfare standards have been documented at some of these events, for example where children have been left in charge of killing baby possums by drowning.

The link between violence towards animals and violence towards humans is well documented and is an area of increasing research and public awareness. The indoctrination of children into a culture of violence around introduced species in New Zealand has been raised as concerning by psychologists working on these issues.


Traps are often used to kill introduced species, especially cats and possums. Traps that kill are tested against a welfare standard, however, this standard permits a proportion of the trapped animals to take up to five minutes to die, a time during which they could suffer severely. Leg-hold traps are also used in New Zealand and these can cause severe pain and distress for animals who become trapped.

Glue traps may also be used. These are generally only allowed to be used to trap insects, however, there are exemptions and glueboard traps have been used to trap mammals (usually mice) in New Zealand during the past five years.

Infectious diseases

Infectious diseases have been released in New Zealand to control rabbit populations. A new strain of rabbit haemorrhagic disease virus was released in 2018 – this virus causes death from internal bleeding, and the rabbit may take several hours to days to die. When this virus was released, effective vaccinations for companion rabbits were in limited supply and those available were expensive, leaving many domestic rabbits at risk from infection.

As resistance to viruses tends to spread widely within a population of animals, the wild rabbit population will inevitably return to previous levels, meaning that all the suffering these animals undergo is pointless.

The humane alternatives

There are alternatives to these cruel approaches to limiting populations of introduced species.

There are many contraceptive options available for different species, ranging from vaccines and hormonal implants in mammals to egg replacement in birds. Different approaches are required for individual situations, however, there are many innovative and effective solutions that can be used under varied circumstances. Gene drives, where infertility genes are spread throughout a population by the release of sterile individuals, are increasingly being considered as a useful approach.

More research is needed into some of these technologies and could be easily prioritised as key research areas by the government.

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