The kidney fat index (KFI) was used to examine the condition of nyala over a 27-m-onth period. From a sample in which both marrow fat and KFI were examined, it was noted that, as has been found in other bovid, kidney fat was mobilized before marrow fat. Seasonal changes in condition were observed and correlated with the rainfall in the previous month. Following periods of less than 50 mm of rain, the larger adult males were in significantly poorer condition than other animals.
The sexual difference in condition is attributed to the differences in body size, where males of asymptotic body mass required 62% more kcal/day than asymptotic mass females. When die-offs occurred during periods of nutritional stress, significantly more old adults died than would be expected. Further, significantly more males died than females.