Before mammals arrived in New Zealand, millions of kiwi thrived as a ground dwelling, ground nesting flightless bird.

Half of All Kiwi Eggs Fail

Today about half of all kiwi eggs fail to hatch – in part due to natural bacteria, in part because the adult bird is disturbed by predators.

Once hatched, kiwi chicks are particularly at risk from stoats and cats.

Of the chicks that do hatch, about 70 per cent are killed by stoats and occasionally cats before they reach six months.  Another 20 per cent die of natural causes, or at the jaws and claws of other types of predator.  Only 10 per cent of kiwi chicks survive to six months of age, and less than five per cent survive to adulthood.

Stoats are a Formidable Predator

Stoats were introduced to New Zealand in an early and failed attempt at bio-control – one of three mustelid species brought here in the 19th century to control a plague of (also) introduced rabbits. The other mustelids are ferrets and weasels.   Tragically, New Zealand’s flightless ground nesting birds, its lizards and its insects proved easier to catch than rabbits. 

Stoats are a particularly effective predator, able to kill kiwi chicks that weigh four or five times more than they do.  Highly mobile and wily, stoats are notoriously difficult to trap.

Wild cats are most likely to kill kiwi chicks once they leave the protection of their parents' burrow, but are still small enough to be caught.  Only when young kiwi reach 1,000 grams, usually at six months of age, are they strong enough and stroppy enough to see off stoats and cats.

Dogs and Ferrets Kill Adult Kiwi

Older kiwi, with their feisty nature, sharp claws and strong legs, are better able defend themselves and can live to well over 20 years.  However, even adult kiwi remain vulnerable to dogs and ferrets. 

Ferrets, also known as fitch or polecat, are the largest of the mustelids.  In one bush patch in Northland, over three months, a single male ferret killed three of 10 breeding males and destroyed two other nests before he was trapped.

While little is currently known about the impact of weasels, the smallest of the mustelids, many experts believe that they could kill kiwi chicks in the first few months of life.

Wild Pigs

Pigs are omnivorous and eat vegetation, insects and other animals.  Although not a major kiwi predator, a pig can easily root out a kiwi burrow.  Sometimes people deliberately (and usually illegally) release wild pigs into the bush to provide hunting quarry.  The consequences for kiwi of wild pigs and pig hunting dogs is a double disaster.  While pig dogs can be trained not to hunt kiwi, wild pigs cannot.