A Shortage of Water in Natural Pastures as a Factor Limiting a Population of Rabbits, Oryctolagus cuniculus (L.), in Arid. North-Eastern South Australia

Abstract

Shortage of water in natural pastures led to a sharp decline in a large rabbit population in arid, northeastern South Australia. The pastures were dry and some rabbits drank at springs and water troughs. Further from water, rabbits climbed trees and shrubs to obtain succulent leaves and twigs. Rabbits provided with water maintained their weight and apparently survived better than those which did not drink. It seems unlikely that the rabbits lost weight because the water shortage reduced the amount of dry food they could eat. In caged rabbits, water shortage limits food intake but also results in low gut fill; whereas the wild rabbits had the normal amount of digesta in their guts. It is more likely that, as the pastures became dry, rabbits ate woody twigs and bark which were moist enough to meet their water requirements but contained too little digestible energy for maintenance. The water shortage apparently arose because rabbits were numerous and had eaten out the succulent pasture plants. Normally, it takes a long drought to reduce arid-zone plants to dry straw, and overgrazing is probably the usual cause of a lack of adequate water for rabbits.