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Competition with livestock over forage resources has been identified as a potential threat to the survival of the African wild ass (Equus africanus) in the Danakil ecosystem (Eritrea). The Messir Plateau is an important breeding area for the African wild ass but also hosts cattle, sheep, goats, donkeys, and camels. Locations and fecal samples of African wild ass and livestock were collected in dry and rainfall months. Stable carbon isotopes [δ 13C ‰] in fecal samples were used to assess diet composition and overlaps with domestic herbivores. Fecal samples also were used to assess the nutritional quality of African wild ass and domestic donkey diets. During the dry months, African wild ass were concentrated in the northern section of the Messir Plateau, approximately 9 km from the permanent water source, and overlapped spatially with local livestock. During the rainfall months, African wild ass dispersed throughout the Messir Plateau (124 km2) when a high number of livestock, particularly cattle from the highlands with herders, were concentrated in the northern section. During the rainfall months, the northern section had relatively better vegetation cover and access to seasonal water. The grass contribution to the diet of the African wild ass in both dry and rainfall months overlapped significantly with that of domestic donkeys and cattle. In rainfall months, the percent fecal nitrogen and phosphorus contents of African wild ass were significantly lower than those of domestic donkey samples. The lower nutrient levels in fecal samples of African wild ass during rainfall months may be due to their displacement from the northern sector by the high number of immigrant highland cattle with people. Our work provides evidence as to how the presence of domestic herbivores, particularly cattle, may negatively impact the nutrient level of wild equids and threaten the survival of the critically endangered African wild ass.

Globally, the African wild ass (Equus africanus) is at risk of extinction in the wild. Major threats to its survival are hunting, competition with livestock, and interbreeding with the domestic donkey. An important but rare population exists on the Messir Plateau in the Danakil ecosystem of Eritrea. Long-term data on reproduction and survival rate of African wild asses are limited, making it difficult to predict the population trend. Therefore, we assessed the population's potential viability given certain assumptions. An age-structured matrix model was used to project the population growth rate generated by assumed vital rates. The probability of population persistence over 50 years was estimated allowing for stochastic dynamics, density dependence, influences of rainfall on carrying capacity, and episodic disturbances reducing survival rates. Scenarios used either historical rainfall patterns or potential future rainfall with the same or amplified coefficient of variation. We contrasted two estimates of carrying capacity based either on recent population assessments, or on the potential capacity of the study site. Our models also compared realistic versus optimistic scenarios for age at first reproduction and potential longevity. The probability of persistence of a population of 18 females was reduced to < 50% in the worst-case scenario. With a potential carrying capacity of 37 females, persistence was projected to be almost 100% under all scenarios. The greatest threat to population viability seems to come from livestock impacts on the resources that limit the African wild ass population size under anticipated climate change scenarios. Further studies are required to assess the level of competition between African wild asses and livestock to guide effective conservation strategies

The critically endangered African wild ass (Equus africanus) occurs in the Danakil Desert of Eritrea and Ethiopia. Drinking behaviour and the costs of accessing water are critical to understanding how this threatened equid survives in an arid environment. Drinking data and distance travelled to water of 24 females and five males were recorded for 83 days during four study years. Drinking frequency per individual per water source was obtained by calculating the number of water visits of an individual per successive days of observation. The travel distance to water was estimated by measuring the distance between the morning foraging location and the water point. During the dry months, female African wild ass with young foals visited permanent water once a day, travelled on average 9 km and drank only at night. Non-reproductive adult females and males travelled to water every 5–10 days. In rainfall months, females with young foals drank twice a day and on average travelled 3 km to water, but dispersed up to 7 km from temporary water sources when livestock arrived annually. This spatial exclusion from water sources due to livestock presence may reduce female African wild ass ability to provide sufficient milk to their foals.