Seasonal variation in water turnover by oryx and eland on the Galana Game Ranch Research Project

Abstract

Measurement of total body water and water turnover was based on the single injection dilution principal using tritiated water.

Under a daylight grazing regime the water turnover varied from 24 to 98 ml/kg/day in oryx and 42 to 121 ml/kg/day in eland. This large seasonal variation was most highly correlated with heat load expressed as solar radiation or mean ambient temperature. Lack of correlation between water turnover and dry matter intake, and low correlation with dietary moisture may have been due to difficulties in measuring these parameters accurately.

When preformed water was calculated by subtraction of drinking and metabolic water from total turnover, it was found to have a positive correlation with turnover rate and a negative correlation with water drunk. Thus high water turnover was not associated with high drinking requirements in either species.

The relationship between climate, pasture and water turnover, could be upset by changes in the activity of the animal from the normal day grazing pattern.

The results obtained from the domestic game animals were used to explain how wild oryx and eland could exploit a hot, semi-arid environment without drinking. To achieve this, the wild animal must obtain most of its nutritional requirements between evening and morning, and its water requirements during the period of maximum relative humidity between midnight and dawn.