The ability of the wild rabbit to survive conditions of water restriction

Abstract

Evidence is presented showing that the wild rabbit, Oryctolagus cuniculus (L.), is able to conserve body water and live through relatively long periods of environmental heat and dryness. Rabbits were kept in a 2-acre enclosure without access to water. After the onset of extremely dry summer conditions, the rabbits lost weight slowly over a period of 2 months, when most died after losing nearly 50% of their original weight. The long survival of the rabbits under the experimental conditions is a result of the efficiency of their mechanisms of water economy. Two such mechanisms were studied; one was the ability to concentrate the urine. The data show that urine concentrations vary in response to availability of water within the range 0.35 to 1.5M urea. The maximum value recorded was 2.OM urea. During severe restriction, urine volume was greatly reduced. The other mechanism of water economy studied was reduction of evaporative water loss. Measurements of burrow temperatures and humidities emphasized the importance of this insular climate as an aid to temperature regulation and water conservation. The burrow was shown to present an environment of moderate, stable temperature and high humidity, which is determined by the temperature and moisture content of the surrounding soil.