An evaluation of diet quality in two desert ungulates exposed to hyper-arid conditions

Abstract

Desert-dwelling ungulates are frequently exposed to plant communities of poor nutritional quality and low abundance. We assessed the diet quality of a large-bodied non-ruminant, the Asiatic wild ass (Equus hemionus) and that of a small-bodied ruminant, the dorcas gazelle (Gazella dorcas) in Makhtesh Ramon, Negev desert, Israel. The diet of the dorcas gazelle was significantly richer in crude protein than that of the wild ass. The level of crude protein in the faeces of dorcas gazelles was higher than that measured in the plant species, suggesting that diet selection by gazelles occurred at the level of plant parts, not species. Wild ass faecal energy was positively correlated with plant species richness and cover of forage species. Faecal digestibility (a measure of dietary fibre content) in both the wild ass and dorcas gazelle was negatively correlated with plant cover. These results are discussed in terms of the ungulates' digestive physiology and body size, as well as their habitat selection.