Effectiveness and Cost-Efficiency of Control of the Wild Rabbit, Oryctolagus Cuniculus (L.), By Combinations of Poisoning, Ripping, Fumigation and Maintenance Fumigation.

Abstract

An experiment compared effectiveness, cost and cost-efficiency of factorial combinations of the four commonly used methods of rabbit control on grazing properties in the Southern Tablelands of eastern Australia. Sixteen different treatment combinations were applied to 32 sites. The treatments comprised initial control, applied over four months, followed by repeated maintenance control on half the replicates, applied after intervals of 2,6 and 12 months. Initial control comprised no treatment, or poisoning (P) with sodium monofluoroacetate (1080), or warren-ripping (R), or chloropicrin pressure fumigation (F), or combinations of these (P+R, P+F, R+F, P+R+F). Maintenance control consisted of phosphine-diffusion fumigation (M). Indices of rabbit abundance were compared one month before treatments were implemented. Treatment effects were assessed one month after completion of the initial control, and one and 5-6 months after the three maintenance controls, and additionally nine months after the second maintenance control. Control combinations that were highly effective and cost-efficient included both warren-ripping and maintenance treatment. Poisoning prior to warren-ripping, or fumigating subsequently, or both, improved effectiveness and cost-efficiency. Warren-ripping interacted positively with one or more subsequent fumigations, improving effectiveness and cost-efficiency non-additively. Control combinations that excluded warren-ripping were ineffective and cost-inefficient, and one combination interacted negatively. Single treatments of poisoning or fumigation were cost-inefficient, allowing rabbits to recolonise rapidly to densities higher than original. Only multiple combination treatments or repeated applications were highly effective and cost-efficient; single applications of any method were inefficient and costly. The most effective and cost-efficient combination comprised the maximum six applications including ripping and maintenance treatment, namely P+R+F+M. The high effort and expenditure on the initial control resulted in high effectiveness and cost-efficiency, which maintenance control sustained at low cost. Maintenance treatments sustained or achieved effective control of rabbits; the cost of maintenance treatments halved on each repetition.