WILD LIFE COMPLEX

Evening Post, Volume CXV, Issue 71, 25 March 1933, Page 12

WILD LIFE COMPLEX

One of the beauties—arid one of the mysteries—of Nature is the interdependence of mid life. Forest, bird, and insect are a trinity, and there is an interchange of services that is beautiful but dazzling in its complexity. Native forest birds defend forest trees from insect and fungoid pests; at the same time the birds live to some extent on the fruits and berries ;..of the trees. Both birds and insects help in pollination and seed-distribution, and have an advantage ove.r; plant-life in being mobile and in some cases migrational. There • was a balance of nature before the arrival of economic civilisation, with its improved methods of destroying bird and bush, and its introduced deer, goats, stoats, opossums, and owls. With the white man has coiiie not only these permitted additions to wild lifej but other animals and birds that have become wild (cats, new rat species, pigs, wild cattle, magpies, etc.), also many insects and fungoid organisms wholly or partly noxious, and many weeds and plants competitive with" the native vegetation. Nature is struggling towards a new balance in wild life, and it has become very difficult to draw up a balance-sheet, because services and disservices as between one wild creature and another are. hard to assess. For instance, the opossum has been charged with killing birds and eating eggs, but this is held to be not proven; only scientific observation and analysis can give satisfactory evidence and verdict. On what looks like, stronger evidence, the opossum is charged with consuming seeds and ' fruits necessary to the birds' seasonal diet and with damaging the forest trees and plant life. And today a correspondent (Mr. G. S. Phillips) says that the opossum's nocturnal rambles in summer frighten nesting birds and cause sufficiently - long nest-desertion to destroy young and eggs. On every one of these counts further evidence is wanted. The test should be scientific, and herein work might be foflnd for the new, Biological Section, of the Wellington Philosophical Society.

Complexity is created not only by ignorance as to, the true value of the above points in, the indictment,, but by many other uncertain values. Until the economic value of deer products is finally proved, the opossum stands out as our only wild animal that provides in itself economic profit and public revenue. Defenders of., the opossum say that, through trapping: revenue—and. if such revenue is earmarked or partly earmarked for wild life defence purposes—the opossum will repay to the birds twice as much as he ever robbed them of in the way of food, nest-desertion, etc. . But that calculation is only a guess until such time as science shall measure with some justice both the service and the disservice. Again, opossum-trapping brings the trapper; he may help indigenous life if he shcots deer and

goats, but not if he shoots pigeons and kakas;- he necessarily cuts the forest about to a certain extent, and the limit of the harm he may do will be set by the degree of effective control over him. On the other hand, it is urged that, as a setter of traps, he necessarily destroys vermin—rats, stoats, weasels, etc. On the evidence of trappers, acclimatisation societies have claimed a high rate of destruction of vermin by trappers, and have calculated therefrom a great saving in bird life. This whole claim should be examined again in a more scientific way. Not only are vermin caught in opossum traps; birds sometimes" are. If the rate of vermin generation, is much greater than that of birds {some of which are said to produce one young per four per year) then the destruction of a few birds may be a more serious loss to the bird, tribe than the destruction of many vermin is to the vermin tribe. The. vermin-trap-ping claim seems to be due for reexamination by disinterested parties. : Other evidence rtliat needs checking is that concerning observed increases of native bird life. Observation of the bird life in the bush seems to Be a poor way of compiling a bird-census unless such observation is carried out all through the .year and in different places. Native birds are found in different parts, of a bush at differpnt hours of the day; in different parts of the country.at different seasons. One may go into a bush at one time and find it apparently full of native birds; on another day it seems a blank. Casual observation is, therefore not /much of a guide as to -whether native birds are increasing or decreasing. Also, the observer .should hate no conscious or unconscious bias.: A man who is against deer will go into the bush and see deer-tracks and deermarks everywhere; a man wlio is for deer will find the bush triumphant and the deer insignificant. A^ an instance, what different. stpries are told of the Kaimanawa country! And the birds are mbre.mobile and elusive than even the deer. The acclimatisation societies have quoted evidence of trappers who, season after season^ noted an observed increase of native birds, "dues of course to trapping." But Mr. Phillips writes today that the Tauherenikau bush, which was trapped for years, but which was not trapped (legally) last winter, is birdless. Can it be believed that one close season, with its amnesty for vermin, has already registered a decrease of birds? Or lias there been (as the correspondent seems to think) a progressive and uninterrupted decrease of birds, unaffected by the trapping of vermin? Evidence, reports, rumours, etc., have drifted into something of a tangle. It would be a great work if the Biological Section, or any competent unbiased authority, would go into the evidence again, try to jassess services and disservices, and, draw up some sort of a Balance-' sheet of wild life to give the public an idea of the drift (for* it is little else) that is taking place and where it is leading. ,