Daily food intake of free-ranging wild rabbits in semiarid South Australia

Abstract

Context Although the daily food intake of wild rabbits is broadly known, precise field estimates have not been made. Moreover, regressions based on metabolic body size and food intake of grazing herbivores in general are too imprecise to provide close predictions. Using such values could result in substantial errors when estimating grazing equivalents to sheep or cattle and resultant economic losses, or estimating the numbers of rabbits per hectare based on rates of deposition of faeces. Aim To re-analyse previously collected data on estimated food digestibility and food intake of rabbits, and provide a framework for better estimating economic and conservation losses attributable to wild rabbits. Methods Food intake of wild free-ranging rabbits was calculated from past measurements of water turnover obtained from dilution of injected tritiated water and estimates of the water content and digestibility of the food eaten. Key results During spring, male rabbits were estimated to eat 65.7 ± 12.5 g dry matter per corrected bodyweight (W–0.75) per day and lactating females ate 97.0 ± 19.4 g dry matter W–0.75 day–1. Similar results were obtained on repetition of trials at a second field site and from wild rabbits held in captivity. Conclusions The estimates of food digestibility and intake obtained, although not precise, are an improvement on theoretical expectations alone and help put previously published data in better perspective. Implications Improved estimates of food consumption provide more confidence in estimates of rabbit grazing pressure. Even moderate densities of rabbits (5 rabbits per ha) could remove about half the pasture produced in an average year in Australia’s arid-zone.