RABBITS INCREASING

Evening Star, Issue 21721, 16 May 1934, Page 7

RABBITS INCREASING

AFTER LOW EBB REACHED SOME OF THE REASONS FARMERS POOR—SKINS CHEAP Rabbits are increasing rapidly in districts where they numbered very few some three years ago, and it is stated by officials of the Department of Agriculture that the increase is general, and that even districts hitherto practically free of rabbits, such as Taraualu and North Auckland, are now menaced. Most people hare noticed rabbits where they have not been seen for years, few though they arc at present. The rapid drop in the rabbit population of the dominion has raised the theory that large areas of country had become " rabbit-sick," owing to overcrowding, and that it was this which accounted for the practical disappearance of rabbits from some districts. This happened in the Marlborough district years ago, and even then the areas so affected were small. Instinct seems to tell the rabbits to leave such areas, and so the net effect is practically negligible. Jn Central Otago, at one time densely overrun by rabbits, no instance of • " rabbit-sick '\ areas is known. EXTERMINATION METHODS, ■ Diseases natural to rabbits at times kill off large numbers. At different times many methods of introducing disease, with the object of exterminating them, have been tried, in IS9B experiments with • chicken cholera, given to the rabbits by means of pellets containing the virus placed where sods had been turned, gave promising results at first. The rabbits found the pellets so attractive that they vanished almost as 'soon as thoy were laid; in fact, as soon as the backs of the men were turned. On some properties the pests were depleted, but for some reason the success of the experiments with rabbits in captivity was not generally duplicated, and as there was a danger of ; the disease spreading to stock the experiments were dropped. One of the reasons for the failure was that tbe rabbits migrated from ■ the affected areas'. Numbers of attempts to cope with the rabbit pest have' been made in Australia, one .idea being to kill off most of tbe does; but this selective decimation moved difficult, the critical" point was never reached, and the rabbits were never faced with the destructive polyandry planned for them. Mauv. forms of disease have, been suggested to accomplish extermination, but none has so far proved practicable and at the same time'safe for stock. The subject has not been lost sight of; indeed, the Government Laboratory at Wallaceville is now studying its problems.

WHY RABBITS ARE INCREASING. The determining factor in the numbers of rabbits is undoubtedly toe price of skins. Unfortunately the maiket is not a local one, and its prices do, not depend upon the number of rabbits in New Zealand. The great reduction of rabbits so noticeable a tew rears ago is held to be entirely due to the high prices paid tor skins sonic years previously. Exports fell from a skins a year t« 6.1(4,000 in 10-31. die falling-oil being probably caused partly by a diminution of the rabbit population when the prices were high, ami also by the effect of the world depression on prices tor skins. During the depression fanners were in many, instances unable to pay lor rabbit poison, in<r while it became more difficult to encourage men to undertake, trapping or'poisoning when the gains to themselves were smaller than iornieily. Thus the rabbits have been less molested than formerly for several consecutive voars, during which the sea--onal conditions lent themselves to rabbit increase. Tn the warmer districts there is an appreciable amount of winter breeding, and the absence or spring floods, which-account tor mil--1 ions of voting rabbits on riverbeds, has helped. The Unemployment board has at , times-, assisted farmers to employ registered unemployed fof poisoning and trapping where the prices .of skins have not formed sufficient inducement to the men themselves, and this policy Tnfiy be reverted to. ARRESTING FIGURES.

The possible danger to the farming community in a period of depression ■.vhen skiii prices are low may be esn : united from a report prepared by Messrs I) Aluiiro and 11. Wright, mallei pal ' inspectors of the Live Stock Division of the Department of Agncuitiiio. Doubling the nails in a horseshoe gives far less surprising results than the unchecked increase of rabbits. Assuming that the average litter is six,” says the report, ‘‘ and that each doe will produce in the year eight litters of equal sexes, and that the young does will breed at fifteen weeks, the total increase for the year from one pair would be 534. This total is contingent upon there being no casualties; hut, allowing that from all causes oO per cent, of this increase will become casualties before‘the beginning ot the second year, the second breeding season would thus commence with a total of 267, plus one of the original pair, a total of 268. Half of this number, 1 ‘ft, arc docs, each producing an increase j3t 634 for the season; 534 X 134=71,556. The casualties during the second year and succeeding years would be less than in the first year, as the toll taken by the natural enemy would not increase in proportion; but allowing that the losses remain at 50 per cent., the third year would start with half year s increase, equalling 35,778, plus 134 does (with which the second season started), equalling 35,912. Half of these, or 17.956, are does, each giving an increase of 534 iu the year: .1 i ,956 X 534=9,588,504. To this must he added the number at the beginning of the season—namely. 35,012 —showing a total of 0,634.416 at the end of the third year. “ It will thus be seen .that it is reasonably possible for one pair of rabbits to increase in three years to between nine and ten millions. This is a fact which it would be well for every settler to fix very clearly in bis mind. The figures stated present an interesting problem. It is estimated that six or seven rabbits will cat or destroy as much grass as would graze one sheep; but, allowing that ten rabbits equal one sheep, it is evident that one pair of rabbits is callable of reducing in_ throe years the stock-carrying capacity of our lands to 'the extent of a million sheep."