Stoats in New Zealand facts for kids

Stoats are small, quick hunters that were brought to New Zealand a long time ago. They were meant to help control the large numbers of rabbits and hares that had also been brought to the country. However, stoats quickly became a big problem for New Zealand's unique native birds.

Before people settled in New Zealand, the only land mammals were bats. Later, settlers from Polynesia and Europe introduced many different animals, including rabbits and stoats. Stoats usually live in the Northern Hemisphere, but they adapted well to New Zealand. Sometimes, in a place called Southland, a stoat's fur can turn completely white. This white fur is called ermine and was once used for royal robes!

Why Stoats Came to New Zealand

European settlers brought rabbits to New Zealand for food and for hunting. By the 1870s, there were so many rabbits that they were destroying farms. Farmers needed a solution to this rabbit problem.

They asked for animals like stoats to be brought in to hunt the rabbits. Some scientists, like Walter Buller from New Zealand, warned that stoats would also hunt native birds. But these warnings were not listened to. Stoats started arriving from Britain in the 1880s. Sadly, within just six years, people noticed that bird numbers were dropping very quickly.

By 1930, a group called the Auckland Acclimatisation Society, which helped bring new animals to New Zealand, started trying to stop the protection of stoats and cats. They realized these animals were harming native wildlife.

How Stoats Spread to Islands

A famous conservationist named Richard Henry tried to move birds to safe islands. But stoats are amazing swimmers! They even swam to Resolution Island, undoing his hard work.

In the early 2000s, stoats were removed from islands like Chalky Island in Fiordland. Scientists thought stoats couldn't cross more than 300 meters of water. But they were wrong! DNA tests showed that stoats regularly swim to islands, especially in summer when there's lots of food. They prefer islands with long coastlines.

In December 2010, a stoat was seen on Kapiti Island, which was thought to be stoat-free. By August the next year, the Department of Conservation had caught and killed three stoats there. It seems unlikely a stoat could swim five kilometers from the mainland to Kapiti Island. However, experiments have shown stoats can swim for two hours without stopping, which is like swimming 1.8 kilometers!

Why Stoats Are a Threat to Birds

New Zealand has many birds that nest on the ground or cannot fly. This is because, for a very long time, there were no land animals that hunted them. Native birds developed to fill roles that mammals play in other parts of the world.

Stoats are the biggest danger to these ground-nesting and hole-nesting birds. These birds have very few ways to escape from a stoat. For example, in some areas, the whio (a native duck) population is now 70% male. This is because stoats attack the female ducks while they are sitting on their eggs.

Stoats and Food Cycles

Besides birds, stoats also eat insects, mice, and rats. Sometimes, southern beech trees produce a huge amount of seeds. This event is called a "beech mast." When this happens, there's a lot more food for rats and mice, so their numbers grow. More rats and mice mean more food for stoats, which leads to more stoat babies.

Once the stoat population grows, they eat many of the rats and mice. Then, with fewer rodents around, the stoats start hunting birds even more. For example, the wild population of the endangered takahe bird dropped by a third between 2006 and 2007. This happened after a stoat "plague" (a huge increase in stoat numbers) wiped out more than half the takahe in areas where stoats were not controlled.

Controlling Stoat Numbers

Stoats are very hard to control. They are careful about new baits and traps, and they have many babies. In areas where endangered birds live, special programs have been set up to trap stoats.

The most common way to trap a stoat is using a stoat tunnel. This is a wooden box with a small opening for the stoat to enter. An egg is often used as bait, and a trap inside the tunnel kills the stoat. New designs for traps that can reset themselves in remote areas are also being tested and look promising.

Protecting Areas from Stoats

"Mainland Islands" are special protected areas on the mainland of New Zealand. These areas have strong programs to control introduced pests. They often have stoat traps around their edges.

Another method is to build predator-proof fences. These fences use fine wire mesh to keep stoats out of protected areas. Scientists are also looking into ways to stop stoats from having so many babies.

Laws About Stoats

Even though people knew stoats could be a problem before they were brought to New Zealand, they were protected by law until 1936. Now, to protect New Zealand's unique plants and animals, there are serious penalties for bringing stoats into protected areas.

Images for kids

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  A stoat in its natural range (in this case the Ardennes in Belgium).