Effectiveness and economics of destruction of rabbit warrens in sandy soils by ripping.

Abstract

The practicability and success of reducing rabbit numbers in a sand-dune habitat in which they survive droughts, by destroyingtheir warrens using a hy- draulically operated ripper mounted on a relatively light-weight wheeled tractor, was examined in a 47 km paddock on a sheep-grazing property in far north- western New South Wales. During the two year experimental period the number of warrens with more than four open holes in the treated area fell from 294to 39 whilethe number in the untreated area varied between 348 and 400. Small warrens with four holes or fewer were not ripped. Their numbers in the treated area increased from 183 to 194 compared with 384 to 406 in the untreated area. However, in the treated area, more increased in size to become large warrens and more new ones were dug than in the untreated area. The total number of active holes, an index of rabbit numbers, fell on the treated area from 3,122 to 397.56% of those remainingoccurred in the unripped small warrens. In the untreated area the number of active holes fell from 3,622 to 3,073. The results show that ripping warrens with a small wheeled tractor is an effective technique for reducing rabbit numbers in sand-dune"survival"areas. Ef- fectiveness is dependent on the ripping programme operating over a series of years with follow-up re-ripping. Missed small warrens can be a source of reinfesta- tion. Examination of the economics of such a programme indicated that the expense of ripping would be more than covered by the returns from increased wool production which might be expected with the reduction in the number of rabbits and by various tax benefits flowing from the