A Study of the Biology of the Wild Rabbit in Climatically Different Regions in Eastern Australia VI.* Changes in Numbers and Distribution related to Climate and Land Systems in Semiarid North-Western New South Wales.

Abstract

This paper describes a dramatic fall in rabbit populations in a large area of semiarid north-western New South Wales, due to a severe drought, and the increase in numbers which followed. The reduction in numbers differed markedly in different land systems. The areas which supported rabbit populations throughout the study were limited to the proximity of swamps in sandy habitats, and close to drainage channels in stony habitats; populations became extinct over large areas of sandy habitats. In the stony habitats populations increased very rapidly in the 12 months following the breaking of the drought, whereas in the sandy habitats it took c. 3 y before a noticeable increase. The difference was probably a result of differences in survival, due mainly to the effects of predation and to the availability of open warrens. In sandy habitats drift sand buried untenanted warrens very rapidly. The environment affected not only rabbits but also their main predators, the fox and the cat. No cats and very few foxes were observed in stony habitats. The main activities of both species were confined to refuge areas in sandy habitats. The most significant correlation between indices of rabbit numbers and indices of use of rabbit warrens was the number of active burrows per unit area of habitat.