THE RABBIT PEST.

Shannon News, 28 November 1924, Page 1

THE RABBIT PEST.

ALARMING POTENTIAL INCREASE. Writing under this heading in the New Zealand Journal of Agriculture,. Mr. D. Munroe, Inspector of Stock in the Wanganui, District, contributes a highly interesting article on the dangers of this serious pest in New Zealand. Prevention Easier than Cure. The article, says Mr. Munroe, is contributed in the hope that experience may be of use to settlers, partir cularly those situated in districts where rabbits have not yet become permanently established, and who. have therefore not had the opportunity of becoming acquainted with the peculiarities and possibilities of the rabbit.

One might suppose in this country where the rabbit menace has driven numbers of men off the land and has been responsible for such a great na.tional. loss, that every settler would be conversant with the subject, and at least have sufficient knowledge to effectively prevent the pest from making further encroachment to clean territory. This, however, is not the case. It is remarkable to ? flnd how little is known concerning the rabbit in districts where it has not actually become a nuisance, and I believe that it is. largely due to this lack of knowledge that the pest is still permitted to spread; on to new country,.continues Mr. Munroe. One frequently hears the statement made (generally by men who have no knowledge of the subject) that rabbits will never do , harm in their particular, district, the reasons given being that there is too much grass, the country is too rich or too wet,the subsoil too hard in, the country too closely settled, etc. —all reasons which I heard thirty years ago in districts which are today rabbit-infested areas. There is no part of New Zealand in which it is either too wet, too dry, too hot, or too cold for the rabbit to prove a very, serious nuisance if given the opportunity of becoming established. It would be a very doubtful recommendation ■to any country to say t that it will not carry rabbits. Potential Increase of Rabbits. . , There appears to be an impression prevail nt i in the minds of settlers inexperienced in the ways of the-rabbit that for an invasion the pestt is going to advance in massed formation of battalions and divisions. I have heard it said by settlers in rabbit-infested districts that, for several years there were only a-few rabbits, and then quite suddenly they came in thousands. Such statements, "no doubt, are largply . responsible for the. mistaken idea' that the pest suddenly: migrates en masse to new country. •', .This, says r. Munroe, is not the case. In order to fully appreciate the danger of the pest it is necessary to realise the extent to which rabbits are capable of increasing in, a given time, and I have worked out a propagation chart" showing in detail what may be con-, sidered a reasonably conservative estimate of the increase from one pair of rabbits in one, two, arid three years. Ten Litters a Year. There is no doubt'that the number of litters which a doe will produce in a season is to a large extent regulated by climatic conditions, a dry, warm season being, of course, most suitable. This point is w£ll demonstrated in New Zealand, where climatic conditons vary a good deal. In the southern part of the bouth island, where the winter months a-e more severe, there is' a distinct brea fc in the breeding seasons of from three to four months. In Southland, Otago, and South Canterbury there is practically no breeding from the beginning of May to the middle of August; but in parts of the North Island, particularlyon the coastal country, where the winter is usually very mild, it is not uncommon to find numbers of nests and young rabbits all through the" winter months. Under ideal conditions it is easily possible for a doe to have ten litters i*a the year (the period of gestation being twenty-eight to thirty days), and, says Mr. Munroe, from records kept over a lengthy period I have found that the average number in the litter is six. In the. early spring months the average is approximately seven, but after November, when the young does come into bearing, the average litter will be found to drop to six. I have, seen on two occasions a litter of fourteen, and litters of ten to twelve are not uncommon.

Higher Mathematics. Assuming; then; that the average litter is six, that each dge will produce in the year eight litters of equal sexes, and that the young does will breed at fifteen weeks, the total crease for the year /from, one pair would be 534. This total i® contingent upon there befog- no casualties; but allowing that from all causes 50 per cent, of this increase will become casualties before the beginning of the second year, the second ( breeding son would thus commence with a. total of. 267, plus one of the original pair—26B. Of this number, half 134 are does, each producing an increase of 534 in the season; 534 plus ,134 equal 71,556. The casualties during the second year and succeeding years would be less than in the first year, as" the requirements of the natural enemy would not increase in proportion; but, allowing that the casualties still remain at 50 per cent., the third year would start with half of the second year's increase—3s,7Bß,. plus 134 (with which the second season started) —35,912. Half of these are does, or 17,956 does, each giving, an in T crease of 534 in the year; 17,956. multiplied by 534 equals 9,588,504. To this must be added the number at the beginning of the season —35..912 — showing a total of 9,624,416 at the end of the third year. -" -

Ten Millions in Three Years. j It will thus be seen that it is reasonably possible for one pair of rabbits to increase in three years to between. 9,000,000 and 10,000,000., This is a fact which it would be well for every settler to fix very clearly in his mind. The figures stated present an interesting problem. It is estimated that six or eight rabbits will eat or

destroy as much grass as would graze *. one sheep; but, allowing that terf;rabbits equal, one sheep, it is evident that one pair of rabbits is capable of reducing in three years thV stock-carry-ing capacity -ot. our. lands to the extent of a million sheep. This affords some indication of the enormous annual loss which the rabbit pest may represent. \