Predators

The Stoat (Kiwi Chick Predator Number One)
Mustela erminea

The Stoat was introduced in the late 1800's to control rabbits and hares. Originally from Europe, it instinctively kills to store food in order to survive the harsh European winter months.

In New Zealand the climate is mild in comparison and there is an abundance of prey that the stoat finds irresistible. Stoats kill every potential food source they see whether they are hungry or not.

• Stoats are now common in all New Zealand native and exotic forests from sea level to above the tree line.
• Stoats are wary, shrewd and notoriously difficult to trap.
• Stoats are considered the biggest threat to all New Zealand native birds.
• Stoats are awesome hunters. They are by far the most threatening predator to all kiwi chicks.
• A one week old kiwi chick, out foraging for food is a ridiculously easy target, and does not stand a chance without human help.

The Dog (Adult Kiwi Predator Number One)
Canis lupus familiaris - this term applies to both feral and domestic dogs.

The dog is the earliest domesticated mammal. A single species, the gray wolf is the common ancestor of all breeds of domestic dog. A dog’s natural abilities - exceptional hearing and sense of smell, powerful muscles, a cardiovascular system that supports sprinting and endurance - all have helped humans literally cross new frontiers in history and are the exact abilities that we need to be wary of in regards to protecting our native wildlife.

An uncontrolled, hungry dog has all of the natural instincts that will ensure its survival. They are predators, scavengers and proficient hunters. Their teeth are built to puncture and tear flesh. Dogs are a huge threat to kiwi because they can kill adult birds. In killing one adult bird, one dog can potentially kill up to 50 seasons of chick production. As an example of how costly one uncontrolled dog can be, over a six week period in 1987, one dog killed at least 500 kiwi out of an estimated population of 900 in Waitangi State Forest in Bay of Islands, devastating this population and which could have been easily prevented.

• Dogs are crepuscular. This means that they are most active at dusk and dawn.
• Dogs are omnivorous but their main food source is meat. Ground nesting birds (kiwi, weka, dotterel and variable oystercatcher) as well as their eggs all feature on a dog’s menu. Dogs will also eat fruit, vegetables, grains and eggs.
• It is estimated that there are 400 million dogs worldwide.

The Ferret
Mustela putorius furo – ‘weasel-like stinky thief’

Five ferrets were imported into New Zealand in 1879 at the request of farmers to control the rabbit population. In 1882 – 1883 five more shipments were made from London and Melbourne. En route to New Zealand, these ferrets were mated with the European Polecat, creating a number of hybrids that were capable of surviving in the wild. These hybrid ferrets ate native birds as well as rabbit. Native birds had previously had no mammalian predators and were easy prey.

Ferrets were farmed in New Zealand in the 1980’s with the vision of creating an export fur trade. When this proved to be a financial flop, the doors were literally opened and all of the ferrets were released. In Northland, this caused an invasion into prime kiwi habitat.

• Ferrets are crepuscular. This means that they are most active at dusk and dawn.
• Ferrets are carnivorous and their main food source is rabbit. Ferrets also eat lizards, insects, penguins, eggs, chicks, weta and flightless birds – including kiwi!
• Ferrets are effective hunters. Their long, lean build means accessing a burrow is easy – kiwi as well as rabbits nest in burrows! Their size means that even adult kiwi are not safe from predation.
• Ferrets have been illegal to sell, distribute or breed in New Zealand since 2002.
• While the domestic ferret has been associated with people for over 2,500 years, and the United States of America has approximately 800 000 domestic ferrets kept as pets, it is claimed.

The Domestic and Feral Cat
Felis cattus

The Cat was intentionally taken onboard ships to control rodents and arrived in New Zealand with explorers. In history, cats have been associated with people for more than 9 500 years.

The form and behavior of the domestic cat are not radically different from those of the feral cat. Domestic cats are perfectly capable of surviving in the wild because of their natural hunting instincts, excellent night vision, hearing and sense of smell.

• Cats are active both day and night.
• Cats are carnivorous and eat birds and rodents.
• Cats are exceptional hunters and are major predators of all of New Zealand’s native birds.
• Cats are the most popular pet in the world.

The Weasel
Mustela nivalis

The Weasel was introduced with the stoat and ferret in the late 1800’s to control rabbits. Their population has not thrived as well as that of the stoat.

• Weasels are active both day and night.
• Weasels are carnivorous and eat rodents, birds, eggs, chicks, lizards and invertebrates.
• Weasels are confident predators and often take on prey much larger than themselves. Nesting birds are particularly easy prey.
• Weasels have long, slender bodies and will follow their prey into burrows - kiwi nest in burrows!
• Weasels will kill more than it can eat and store it in a den for future meals.

The Pig
Sus scrofa – this term applies to the domestic and feral pig

The pig was first introduced to New Zealand in 1769 by the French Explorer Jean Francois Marie de Surville but the fate of these pigs is unknown. Captain James Cook then brought them as a gift for Maori in 1773. At this time, New Zealand had no land mammals (apart from bats), the pig had no natural competitors or predators and their population soared. European settlers also helped their population thrive by introducing them into what they saw as empty forests. By 1840 their population was well established and they became the first introduced animal to be hunted for sport.

• Pigs are mainly nocturnal but this does vary among individuals.
• Pigs are omnivorous and are known to eat fern roots, lizards, mushrooms, lambs, eggs and chicks of ground nesting birds.
• In 1988 it was estimated that over 100,000 feral pigs were killed by 23,000 pig hunters.
• Accompanying the threat of pigs to New Zealand’s native birds and animals is the threat of the dogs that work with a hunter. Often a pig hunter will have a pack of dogs to find, bail and hold. Should a dog be injured during a pig hunt or lost, it will use its natural instincts to survive.
• Many hunters now fit their dogs with transmitters before going hunting and many pig hunting clubs now insist that their members have their dogs’ avian averted.
• Refer to information provided on dogs..

The Possum (Hairy-tail little fox)
Trichosurus vulpecula

The Possum was introduced in 1837 to establish a fur trade. Originally from Australia, its population there is controlled through bushfires, predators and less palatable vegetation.

In New Zealand the natural mechanisms of population control do not exist and our possum population is estimated at 70 million. That's a lot of zeros!

• Possums are now found on 90% of the New Zealand mainland.
• Possums eat new growth on trees and can damage entire tree canopies. Their favourite native trees are totara, kowhai, rata, kohekohe and titoki.
• Possums compete with native birds for habitat and food. They eat insects, berries, eggs, chicks and disturb nesting birds.

The Norway or Brown Rat
Rattus norvegicus

The Norway or Brown Rat arrived in New Zealand before 1800, possibly on one of Captain James Cook's vessels. It is generally accepted that it originated in northern China and not in Norway as the name misleads. It has spread to every continent except for Antarctica and is considered the most successful mammal on the planet after humans.

Brown rats are active at night and are great swimmers, but very poor at climbing. In New Zealand these rats devastate our native bird population because they eat ground nesting birds as well as their eggs and chicks, and lizards.

The only brown rat-free zones in the world are the Arctic, Antarctic, some especially isolated islands, the province of Alberta in Canada and certain conservation areas in New Zealand. In New Zealand, these conservation areas are offshore islands and ecological islands on the mainland.

Before an eradication programme was launched in 2001, Campbell Island (New Zealand), in the sub-Antarctic, had the highest population density of brown rat in the world.

The Ship or Black Rat
Rattus rattus

The Ship or Black rat arrived in New Zealand with European explorers. Originally from Asia, its population in New Zealand is abundant. This is attributed to the lack of native land-based mammals, especially other rodents.

• Ship rats are nocturnal and are great climbers, but very poor at swimming.
• Ship rats are omnivorous and eat small forest birds as well as their eggs and chicks, native fruits and seeds, invertebrates and lizards.
• Ship rats are able to carry a number of pathogens, including the bubonic plague (via the rat flea).
• Ship rats are key ecosystem changers, and controlling their abundance is crucial for conservation management.

How can you tell the difference between a Norway and a Ship rat?

There are two easy ways to tell the difference between the Norway and the Ship rat:

1. 1. A Ship rat’s tail reaches his nose
2. 2. A Ship rat’s ears are big enough to cover his eyes.

A Norway rat cannot do either of these.

The Hedgehog
Erinaceus europaeus

The hedgehog was introduced to New Zealand in 1869 to control insects and garden pests. Brought from England, the population of this small mammal in New Zealand is abundant. This is attributed to a lack of natural predators and because many people do not see them as a pest and so don’t trap for them as they would a rat.

• Hedgehogs are nocturnal.
• Hedgehogs are omnivorous and their main food source is invertebrates. As their population has soared their diet has extended to include snails and worms to compensate for the lack of insects.
• Hedgehogs also eat eggs and chicks of ground nesting birds, especially shorebirds like the dotterel.
• Hedgehogs are protected in the United Kingdom.
• Hedgehogs can swim.

Further information

For more information on predators, visit the Department of Conservation website.