Why were stoats and ferrets introduced to New Zealand?

The other day, a colleague of mine asked: “Why were stoats and ferrets introduced into New Zealand? Do you know?”. I put on my best “all-knowing” face, and said “To control rabbits”. But even as I said it, I wavered with uncertainty, because it seemed so preposterous – a bit like the old lady who swallowed the spider (to eat the fly). So, when I had the chance, I investigated (which wasn’t hard – even WikiAnswers helpfully provides an answer to this precise question), and confirmed that, while utterly preposterous as it may be to us in hindsight, mustelids (stoats, ferrets and weasels) were indeed introduced with the primary objective of controlling rabbits.

Rabbits had been introduced from the 1830s to provide food and sport, however, within decades they had become an agricultural pest, reaching plague proportions in some areas [see earlier post on the history of the rabbit in New Zealand]. Farmers put pressure on the government to introduce mustelids, and in the 1870s and 1880s – despite warnings about the likely impact on birds made by naturalists at the time – numerous shipments of these small but fierce hunters had been brought over.

Stoats, ferrets and weasels were the rabbits’ natural enemy in Britain, and it was assumed by most that that same relationship would play out in New Zealand. However, New Zealand’s indigenous birds, which were unused to mammal predators and many of which had no, or only limited flight, proved far more tempting and much less energy-intensive prey than rabbits. Stoats (Mustela erminea) in particular proved deadly to many of our avian fauna. Not only are they determined hunters, they are excellent climbers and good swimmers. Together with rats and cats, stoats have contributed to the extinction of huia, bush wrens, native thrushes, laughing owls and quails. They also helped to decimate the remaining populations of stitchbirds, saddlebacks, kākāpō and little spotted kiwi from the mainland of New Zealand.

By 1903 the government had changed its policy on introducing mustelids, but official protection of the animals remained under the 1886 Rabbit Nuisance Act until 1936.

See also: The attack of the killer bunny.

Photo top and above right: Looking at these photos of a stoat (top) and ferret (above right), it is hard to believe that these handsome creatures are fierce hunters that have wreaked havoc on our indigenous birdlife. Photos copyright Nga Manu Images.

Sources/further reading: Introduced animal pests, Te Ara Encyclopedia of New Zealand; Mustelids, Christchurch City Libraries.

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