Title: Exotic Intruders

Author: Joan Druett

Publication details: Heinemann, 1983, Auckland

Digital publication kindly authorised by: Joan Druett

Part of: New Zealand Texts Collection

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Exotic Intruders

The thrush, the slug and the snail

page 112

The thrush, the slug and the snail

In 1867 a Mr Fereday of Christchurch complained that he had seen ten common English slugs on one cabbage in his garden and used this as an argument for the introduction of birds such as thrushes.

Along with their close cousins, the snails, slugs had been unwittingly introduced to New Zealand in the soil around plants and other garden stuff. In spite of the introduction of birds and other enemies such as hedgehogs, they are now extraordinarily abundant and everyone is familiar with them as a pest. Suter, in the Manual of New ZealandMollusca, 1913, reported, 'In 1887 I was living on a ten-acre [four hectare] clearing in the Forty-Mile Bush, surrounded by native bush. This clearing had been laid down in grass about ten years earlier, and was used for feeding horses. Everywhere (slugs were) common, but these slugs never penetrated the native bush. They evidently must have been brought to that place with the grass seed, and no doubt in the egg state.'

The study of another introduced slug, Limax (the tiger or leopard slug) produced evidence that it was infested with a mite similar to one found infesting it in England. A theory was put forward that the animal had arrived in New Zealand in the adult state, but this seems unlikely, as it is commonly 15-20 centimetres long!

According to Mr Suter, the common or garden snail, Helix aspersa, was noticed first at coastal towns, indicating that it might have arrived attached to the underneath of shipboard crates, or even in dumped ballast. In the early colonies of North America, when snails made their appearance in the gardens, some people accused French pioneers of deliberately importing them for food. However this theory was not advanced in New Zealand, and there is no evidence that snails are more plentiful in the Akaroa area.

The hardiness of the snail family is not appreciated by most people. H. W. Kew recorded a case in England where thirteen snails were taken from the three-day-old corpse of a wood pigeon as part of the stomach contents, which were put in a bowl containing water. Most of the snails immediately began creeping about.

Thrushes are very fond of snails, which they carry to some favourite hard surface, known as an 'anvil stone', where they smash the shell so they can eat the succulent interior. Because of this they were among the earliest of exotic birds to be imported into New Zealand, being first landed in 1862 at Nelson. Many more shipments followed and the thrush established itself quickly and is now abundant throughout the country.

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