Stoat facts and control tips

Stoats, together with ferrets and weasels, were brought to New Zealand during the late nineteenth century in an attempt to reduce the rapidly growing rabbit population. Local scientists, including the well-known ornithologist Walter Buller, warned authorities about the possible consequences, but their concerns were not acted upon.

Once released, stoats quickly became a serious threat to New Zealand’s native birds. Their ability to hunt efficiently allowed them to spread through many parts of the country and severely affect vulnerable wildlife. In fact, until 1936, stoats, ferrets and weasels were legally protected because they were considered useful for controlling rabbits.

What Do Stoats Look Like?

Stoats are members of the mustelid family, the same group that includes weasels and ferrets. In terms of size, they fall between the two, being larger than weasels but generally smaller than ferrets.

They have a slender body, a dark brown or blackish coat, and a lighter-colored belly and throat. One of their most recognizable features is their relatively bushy tail, which ends in a distinctive black tip.

Where Do Stoats Live?

Stoats are now widely distributed throughout Aotearoa New Zealand. They are highly adaptable and can settle almost anywhere that provides access to suitable prey.

They can be encountered in high-country landscapes, coastal areas, farmland, scrub, native bush and forests. Their ability to tolerate challenging environments also allows them to live at high elevations, including areas above the natural tree line.

What Is Known About Stoat Behaviour?

Stoats have excellent vision, strong hearing and a highly developed sense of smell. They are active both during daylight and at night, and their slim bodies allow them to move rapidly through a variety of environments.

They are capable climbers and can scale trees to reach bird nests containing eggs or young chicks. On the ground, they investigate burrows, holes and other hiding places. When they encounter a ground-nesting bird, escaping from the predator can be extremely difficult.

Stoats do not always stop hunting after obtaining enough food for immediate survival. When circumstances allow, they may kill additional animals and store the remains in their dens for later consumption. Despite their relatively small size, stoats can attack and kill prey considerably larger than themselves. They also tend to establish hidden den sites that are difficult to locate.

These predators are capable of covering impressive distances. One young stoat was recorded traveling approximately 70 kilometers in only two weeks. They are also accomplished swimmers and can cross stretches of water measuring a kilometer or more in order to reach islands.

Stoats are intelligent and cautious animals, which makes population control particularly challenging. They can be wary of unfamiliar bait and traps, meaning that effective control often requires careful planning and consistent effort.

What Impact Do Stoats Have on Native Wildlife?

The Department of Conservation has described stoats as one of the most serious predators threatening New Zealand’s native birds. Their persistent hunting behavior can have a major impact on species such as wrybills, New Zealand dotterels, black-fronted terns and young kiwi.

The survival rate of brown kiwi chicks in Northland is particularly concerning. Only around 5% survive to adulthood, with stoats and feral cats identified as major causes of mortality.

Birds that nest inside tree cavities are also vulnerable. Species such as mohua, kākā and yellow-crowned kākāriki can be exposed to stoats when the predators search tree hollows for eggs and young.

Although stoats mainly prey on rats, mice, birds, rabbits, hares, possums and insects such as wētā, their diet is highly flexible. They may also consume lizards, freshwater crayfish, animals killed on roads, hedgehogs and fish when these food sources are available.

Why Are Stoats So Difficult to Control?

Another major problem is the stoat’s remarkable reproductive ability. A female can produce as many as 12 young in a litter, although four to six kits is more typical.

Even more surprisingly, a female stoat can become pregnant when she is only two or three weeks old. At this stage, she is still blind, deaf, without teeth and covered by very little fur.

Despite becoming pregnant so early, the embryos do not immediately continue developing inside her. Their development is delayed until she reaches adulthood, and the young are eventually born during the following spring.

This unusual reproductive strategy allows stoat populations to increase rapidly when food and habitat conditions are favorable.

How Can You Help Control Stoats?

The most reliable approach to reducing stoat numbers is persistent and regular trapping. Trapping programs need to be maintained over time rather than carried out only occasionally.

Use an animal-welfare-approved trap designed for stoats, such as a DOC 200, a DOC 250 from an approved supplier, or a Smart Trap from Goodnature. Suitable places for traps include along fence lines, beneath hedges, beside streams, near fallen logs and around exposed tree roots. Keep the entrances unobstructed by vegetation, leaves or other debris.

Eggs or fresh meat can be used as bait. During warmer summer conditions, salted meat can remain effective for longer. If cats are present in the area, eggs are a preferable option because using meat may create an unnecessary attraction for them.

Traps should be inspected regularly, at least once every month, and old bait should be replaced when necessary.

Always wear protective gloves when handling traps or captured animals. Regular monitoring, appropriate trap placement and continued maintenance can all contribute to reducing stoat numbers and protecting New Zealand’s vulnerable native wildlife.