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

Preface

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Preface

It has been a special pleasure, for several good reasons, to read Exotic Intruders. Firstly, such a complete updated record of acclimatisations, successful or otherwise, has long been overdue. Secondly, it caters for that deep, nostalgic interest which begins early in life and might better be described as a natural acquisitive instinct, seeking closer acquaintance with interesting animals and plants.

Most of us will remember that youthful possessiveness—some would call it predation—which, even before we are old enough to walk, compels us to reach for and clutch a living object—a flower, a small bird, a household cat or dog. It rapidly developed in me, as a boy, in hunting for and collecting butterflies and wild birds' eggs. In my sisters, it took the form of collecting wild flowers. As young children (there were six of us) we set up and shared between us a sort of museum-zoo in a disused kitchen at the back of the house. We pressed wild plants between the leaves of exercise books and kept them on the shelves of the old kitchen dresser, alongside boxes of birds' eggs in cottonwool, and butterflies pinned in glass-covered trays.

Of continuing interest, and trouble, were living creatures. In the old sinks and wash tubs we kept the small life that we had collected in the countryside—tadpoles developing into frogs, toads or newts, and such fish as sticklebat, bully and minnow, freshwater crayfish and shrimps, and water plants. In fact we eagerly welcomed any wildlife; our meagre pocket money was sometimes spent on an exotic tortoise, imported salamander or guinea-pig, obtained at the local petshop.

Sometimes the old kitchen was a hospital for a wounded hedgehog or bird, and more than once a harmless grass-snake, picked up as a casualty on the road. In the little garden plot each of us was allowed to claim as sacred to oneself we grew what our fancy dictated. I remember mine once held captive a toad on a tiny stone island in the centre of a wooden tub half filled with a 'sea' of tapwater. We made-believe he was enchanted, waiting for the spell to be broken which would turn him into a handsome fairy prince. The truth is he was at that period in his toad life-cycle when he had no inclination to go a-wooing but was happy just to sit in the shelter of my stone island snapping up with sticky tongue passing or offered insects, too lethargic to bother to cross the 25 centimetre-wide sea and climb the wooden wall of the tub. My younger sisters were prepared to believe the fairy-tale.

Later we undertook the greater responsibility (as our parents warned us) of keeping and trying to breed a variety of pet mammals and birds. These included page break imported sorts—largely to augment our pocket money. Not infrequently some escaped into the local fields and woods, their fate rarely known.

The child is father and mother of the adult; and thus, when during the last century our pioneering Pakeha forbears emigrated, under stress of adverse economic factors (and notably in the case of New Zealand with a keen appetite for both adventure and wealth) they longed to import into their adopted land the familiar well-loved plants and animals of home, those species which the author of this book fittingly calls 'exotic intruders'.

For me as a naturalist this aspect of Pakeha settlement is of the deepest interest, not to say concern. So much so that I could wish I had been able to research and write such a book myself. Instead I am delighted Joan Druett has achieved this new comprehensive, attractively illustrated appraisal of the acclimatisation of introduced fauna and flora in New Zealand.

This she has done with a readability, spiced with humour, which is certain to make the book popular as well as authoritative. Her human characters come alive with the amusing descriptions of their hopeful, often hopeless, schemes to reconstruct the best of the living faunal and floral scenes of the land they had abandoned. They were mostly 'good' types, these pioneers of a century or more ago, many were the aristocratic sons and daughters of English and Scottish upper class, with a healthy mixture of hardy shepherds and labourers imported to assist. Many of these latter soon rose by sheer hard work to enjoy a share of the wealth and opportunities to be obtained from exploiting the resources of the virgin land. They too, enthusiastically joined the proliferating acclimatisation societies; perhaps with a keener regard for the introduced species which would be most profitable to the economy—rather than the merely ornamental which were cherished by the squirearchy. As the author relates, a positive frenzy of exotic introductions took place at this period with almost total disregard for the consequences to the endemic wildlife, and its fragile ecosystem. The word 'ecosystem' had not yet been invented but its nearest equivalent—the 'Balance of Nature'—was discussed by Darwin in The Origin of Species under the heading: 'Complex Relations of all Animals and Plants to each other in the Struggle for Existence'.

In his book first published in 1859, long after his visit to New Zealand in 1835, Darwin already foresaw the dangers and advantages of acclimatising exotic species: 'From the extraordinary manner in which European productions have recently spread over New Zealand, and have seized on places which must have been previously occupied by the indigenes, we must believe that if all the animals and plants of Great Britain were set free in New Zealand, a multitude of British forms would in the course of time become thoroughly naturalised there, and would exterminate many of the natives.'

This prophetic view, of course, accords with Darwin's theory, also held by Agassiz and other competent observers; that 'ancient' animals, isolated on small islands, and long settled in possession of their ecological niche, tend to remain ancient. They are rather like living fossils, with no defence against vigorous, aggressive intruders whose vigour and aggression in their native country have secured them success in life, making them potentially dominant as colonists in a new land.

Nothing succeeds like success. Joan Druett first documents the success of New Zealand's most formidable exotic intruder of all, the Pakeha colonist, whose superior skill in the arts of metal-working, communications, land-use and warfare at first overwhelmed the Maori tribal system. The Maori population, held in a centuries-long natural balance of numbers limited by the restricted food supply of fish, roots page break and birds, and by the practice of cannibalism, wilted to one-quarter of the number (around 100,000) estimated by Captain Cook 200 years earlier. The first Pakeha to set foot in New Zealand, Cook, correctly surmised that the tribes were too hostile to each other ever to combine effectively to fight the white colonists. Instead, well trained in tribal warfare, and utu (a head for a head) the Maori seized on the musket, not to shoot the Pakeha invader, but principally to slaughter rival neighbouring tribes.

Yet it is said that more Maoris died of Pakeha diseases than by the bullet as they had little resistance and no anti-body immunity to influenza, venereal and the many pox diseases introduced by the early visiting white seamen. So many died that it was even suggested the Maori race would disappear!

Darwin praised the orderly and English appearance of the white missionary station at the Bay of Islands, with its farmlands growing wheat and barley, its grazing cattle, and its gardens rich in many varieties of exotic vegetables and fruits. By contrast he found the Maori villagers there debased by the white traders, many of whom were escaped convicts from Australia who had become beachcombers and layabouts, selling grog and procuring wahines for visiting seamen—'the very refuse of society'.

Into this fertile land, bereft by war and disease of most of its former Polynesian population, poured the hundreds of genuine land-hungry settlers of tough British stock. There were as yet no roads, but there were safe havens for sailing ships. Joan Druett describes how the pioneers spread over the 'Promised Land' from the bridgeheads of many enclosed bays as far south as what is now Dunedin and Stewart Island (stopovers first used by British, Australian and American whaling and sealing ships in the first two decades of the nineteenth century).

Until the Treaty of Waitangi was signed in 1840 forbidding any land to be sold by the Maori tribal owners without special authority of the Queen's representative—the Governor, many settlers or groups of settlers acquired large holdings by barter of a few blankets, hatchets or muskets with local Maori chiefs, most of whom could neither read nor do more than put a mark to the deed of purchase. It is rumoured that one Australian speculator claimed he had bought the whole of the South Island in this way!

Against this early background of land-grabbing during the aggressive colonial settlement of New Zealand, the author entertains us with the full story of the ensuing massive introductions of exotic flora and fauna. At least 550 species of foreign plants have been acclimatised, including the accidental introduction of numerous common weeds whose seeds have sometimes arrived stuck to clothing, or concealed within the once-fashionable turn-ups of trousers. We learn that of about 130 species of foreign birds deliberately introduced, only thirty have become successfully established.

Of numerous introduced land mammals, excluding domesticated farm animals but including self-introduced rats and mice escaped from ships, again only thirty species have since flourished. Into New Zealand's numerous lakes and rivers the new acclimatisation societies eagerly released the larger sorts of foreign edible and sporting fish, with, at first, considerable success. Many grew twice as large as they did in their northern hemisphere homes, but at the expense of the much smaller endemic fishes, some of which are now close to extinction, and one—the New Zealand grayling—almost certainly extinct. Their decline was also due to early logging practices which choked the shady breeding streams, and filled them with silt run-off. Fire also helped to reduce the insect life on which native fish depend for survival. Today we see the result of this continuing degradation of the natural water habitat in the decline of the average weight of exotic fish taken by anglers in our lakes and rivers.

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Insects, of course, have played a highly significant part in this story of exotic intruders, both as self-introduced pests and beneficial anti-pests deliberately released. Joan Druett brings us up to date on the fascinating research into this 'biological warfare' of the DSIR and other scientists—a means of controlling insect predators plaguing forest, farm, orchard and horticultural crops. The natural external and internal parasites which accompanied their imported domestic and wild animal hosts do not escape the author's wide-ranging net. And we learn too, of the success and failure of introduced amphibians; the frogs, toads and other aquatic beasts, and of reptiles, snails and others.

Today we may review with mixed feelings the conseqences of what is called the advance of civilisation upon a once pristine mammal-less archipelago, isolated for so long in the vast Pacific Ocean. We have learned, rather too late, the lesson of randomly introducing hundreds of exotic species. But it is also true that our present, relatively affluent, well-fed and isolated society could not thrive at its present level of population (more than ten times as large as it was a century ago) without the support of the highly productive, renewable resources of exotic food, plants and animals.

Should the reader long to view briefly the living New Zealand of a thousand years ago, before the arrival of the first Maori with his dog and little Polynesian rat, when the land was tall climax forest, loud with the songs of endemic birds untroubled by mammalian predators, it is still possible to do so. By accident of isolation, exposure to weather and lack of a safe harbour and land suitable for food crops, a few small offshore islands remain as they were then. They are very few, and precious as living museums recording the state of the fauna and flora of New Zealand soon after the last glacial period, perhaps 20 000 years ago. We have visited some, including the sub-Antarctic islands of the Snares, and Adams Island in the Auckland group, which have no land mammals.

Over 70 years ago that perceptive botanist, Cockayne, in New Zealand Plants and Their Story wrote that 'the warfare between the primitive New Zealand plant inhabitants and the alien invaders is waged almost entirely under conditions where man takes a hand ... no truly primitive plant formation is desecrated by a single foreign invader.' In other words, were man to depart, were he to take with him every introduced four-footed camp follower then the New Zealand soil, where there are enough endemic trees surviving to provide the seed, would gradually revert to original forest. Natural undergrowth—the light-penetrated understorey which is such a beautiful feature of our native forest—would reappear, and the humus floor resume its soft covering of ferns, orchids and mosses.

A classic example of this regeneration of the New Zealand rainforest is Little Barrier Island, about 3050 hectares large, compact, mountainous to 722 metres and isolated in the Hauraki Gulf some 24 kilometres from the Northland shore. It was formerly exploited for its extensive kauri stand; at least a third of this forest cover was destroyed to supply timber during the development of Auckland City in the last century. But since 1894, when the Government purchased and declared the island a permanent nature reserve, and all domestic animals were removed (save a nucleus enclosed in a grass paddock for the use of the resident ranger), Little Barrier has rapidly reverted to original endemic forest. The last feral cats which had threatened with extinction the stitchbird, a handsome small honey-eater found only on Little Barrier, have lately been eliminated. Only the small kiore rat remains. It is native to many Polynesian rainforest islands, is largely vegetarian, and has little or no effect on the endemic native birds.

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Field studies at Little Barrier have monitored the effect of this removal of predatory and browsing mammals. Stitchbirds are now abundant, along with the nectar-loving bellbird and tui. Other endemic forest birds becoming scarce on the mainland are numerous: the whitehead, rifleman, kaka parrot, kakariki parakeet, pied tit, robin, and two petrels which nest in burrows on the higher ground. They are Cook's and the black petrels which are now rare, as breeders elsewhere in New Zealand, because of mammal predation.

So remarkable has been the recovery of wildlife on this island sanctuary that other rare birds, highly endangered elsewhere in their last forest haunts, are being translocated to Little Barrier—the flightless kakapo or ground parrot, the weak-winged kokako or blue-wattled crow, and the saddleback. Meanwhile botanists report that as the endemic forest of tall kauri, rata and tawhero with its ferny understorey reasserts its dominance, the few alien plants (some seeds carried on the clothes or footwear of human visitors) which appear at intervals, do not succeed in establishing. Nor do the few exotic birds which arrive and settle for a while on the strip of grassland maintained for grazing by the resident ranger's farm stock penetrate far into the maturing natural rainforerst.

There is a moral to be found somewhere in this tale of exotic intruders. The present Government prohibition upon further importations without special permit is like closing the stable door after the horse has bolted. As long ago as 1929, when discussing the ecological effects of acclimatisation in New Zealand, D.L. Poppelwell wrote that 'the remedy is to try and minimize future damage. Steps should be at once taken to destroy the animals introduced for sport only . . .'

Little did Mr Poppelwell realise that the deer which were destroying native forest at that time by devouring the understorey and regenerating saplings, would become a national asset in the present highly profitable export of venison and velvet.

Reading this light-heartedly written yet erudite history of how innumerable exotic plant and animal species arrived, thrived, or died out, you will realise that the British settlers' dream of recreating Britain in New Zealand has largely come true. Every year in almost every way the open New Zealand countryside becomes more British, more dominated by British animals and plants. Whether we like it or not the majority of truly endemic New Zealand birds, reptiles, large snails and insects are disappearing fast, some few having become extinct early in the present century. The native birds are being replaced by increasing flocks of British birds so much better equipped for surviving predation from introduced wild cats, pigs and mustelids, and from aerial predators such as the owls and hawks, which are their natural enemies at home.

Without those 'charms' of goldfinches, flurries of greenfinches, chirping yellowhammers, pretty-plumaged chaffinches, murmurations of starlings—New Zealand's paddocks, gardens, exotic bush and open shore would be duller. We can be thankful that they fill in increasing numbers the gap left by the vanishing endemics. Native bush, even large endemic forests in wild country on the mainland of New Zealand, is very nearly birdless by comparison, because of the presence of predatory introduced mammals. It often contains more exotic bush birds—blackbird, thrush, dunnock and finches than native birds; although as yet these foreigners have not thoroughly adapted to pure stands of native forest.

One detests the opossum for eating choice plants and the tops of trees, but we are obliged to live with them. Pretty as they may be with their bold eyes and baby face, they flourish excessively because they have no natural controls as they have in their page break native Australia, where eagles and large owls reduce their numbers. In Britain native red squirrels browse trees and fruit like opossums, but there they have natural controls in the arboreal mustelids pine marten, and wood owls and hawks. (Squirrels failed to acclimatise in New Zealand.)

Exotic Intruders is a splendidly comprehensive review of the history and facts of man's free-and-easy meddling with nature, one which has set the pristine ecology of New Zealand askew by releasing this Noah's Ark of exotic animals and a cornucopia of foreign plants. With engaging humour the author details the fate of the principal intruders, successful or otherwise, attributing more to good luck than good judgement. It is too late today for conservationists to lament; we must live with the result. But we must also look to the future; we must learn from our experience, exhibit more care and police more rigorously live imports and the goods containing them. Optimistically she concludes that at the present time New Zealand is settling down to a more balanced and resilient ecology than ever before. The weak and delicate among both native and introduced species have died out and our wildlife is emerging as a stronger, richer amalgam of old and new, native and introduced. It is unique, and worthy of preservation.

R.M. Lockley

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