The forage maturation hypothesis (FMH) states that energy intake for ungulates is maximised when forage biomass is at intermediate levels. Nevertheless, metabolic allometry and different digestive systems suggest that resource selection should vary across ungulate species. By combining GPS relocations with remotely sensed data on forage characteristics and surface water, we quantified the effect of body size and digestive system in determining movements of 30 populations of hindgut fermenters (equids) and ruminants across biomes. Selection for intermediate forage biomass was negatively related to body size, regardless of digestive system. Selection for proximity to surface water was stronger for equids relative to ruminants, regardless of body size. To be more generalisable, we suggest that the FMH explicitly incorporate contingencies in body size and digestive system, with small‐bodied ruminants selecting more strongly for potential energy intake, and hindgut fermenters selecting more strongly for surface water.

Depredation by wolves (Canis lupus) could threaten survival of reintroduced wild Przewalski horses (Equus ferus przewalskii) in Hustai National Park (HNP), Mongolia. We conducted scat analysis, spatial analyses of kills, and interviews to study prey species selection and temporal and spatial factors that characterize prey choices of wolves. Diet of wolves in HNP was comprised of >50% of livestock. Diet composition varied during the year, with more livestock taken in winter. Wildlife species were selected over livestock species. From available livestock species domestic horses were predated most, whereas red deer (Cervus elaphus) and marmot (Marmota sibirica) were the preferred wildlife species. Our spatial analyses showed an unexpected significant positive relation between number of domestic horses killed and distance to the park, as well as a significant negative relation with number of gers (tents) in the area. Compared to randomly selected comparison sites (n = 36), we found Przewalski foal kills (n = 36) at sites that were closer to the forest, at higher altitudes, with lower shrub cover, higher forest cover, and higher red deer density. If the negative trend of deer numbers continues and if herdsmen protect their livestock more vigorously, depredation of wild Przewalski horses by wolves will rise. Therefore, a large red deer population could be pivotal in improving the conservation status of Przewalski horses.

Re-introduced Przewalski horses in Hustai National Park, Mongolia could suffer from food competition with other herbivore species through food resource depletion. Diet composition of the Przewalski horse (Equus ferus przewalskii), red deer (Cervus elaphus) and four livestock species (sheep, goat, cattle and horse) were studied, using micro histological analysis of faecal samples in the summer of 2005 and winter of 2006 -2007. We expected that herbivores become less selective in food choice in winter regarding to summer, resulting in a larger diet breadth, a larger similarity in diet and a larger dietary overlap in winter, potentially triggering exploitative competition by depletion of shared resources. Vegetation biomass decreased during winter, and the different herbivores species in HNP changed their diet from summer to winter. As expected diet breadth, diet similarity and dietary overlap were significantly larger in winter in comparison to summer. The existence of competition by resource depletion between the different species cannot be ruled out. Vegetation biomass was probably not a limiting factor according to the correlation between annual rainfall and herbivore species biomass, however the forage quality may be limiting, triggering competition.

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