Group Composition and Behavior of Equus Hemionus Near a Water Source in the Negev Desert

The Asiatic Wild Ass, Equus hemionus, was once abundant in western Asia. The species declined due to hunting and habitat loss. Between 1982-93 38 E. hemionus (21♀ 17♂) were reintroduced to the Negev Desert, Israel. Saltz, Rubinstein and co-workers studied the released population till 1999. The current population in the Negev is estimated at more than 200 individuals, yet, their social structure is not known. Here we report group composition and behavior of E. hemionus near a water source. We recorded and videotaped in 2010 group composition and social interactions from a shelter, 150m from the water source. Not all wild asses were individually identified, but so far, we created 97 individual profiles (27♀ 70♂) based on photos, and recorded in which groups were they videotaped. Individuals were recognized with certainty up to 9 times, but 73 individuals were identified only once. Before reaching the water source, wild asses often aggregate in large groups and wait for the first few individuals to approach cautiously the water, and only then the rest of the individuals make a swift final approach. We did not consider these aggregations as social groups. We defined a group when individuals approached or left together the valley in which the water source is located. Female groups (including those with a male) were larger than male-only groups (9.8 and 5.1 individuals, range 2-49 and 1-34, respectively; P = 0.0191). Individuals appear on different days in groups of various sizes and compositions. The highest proportion of juveniles per female was seen in Nov. (0.74; P = 0.04) and this value is comparable to that found in the 1990’s study (0.75). Except for Sep., fewer adult females were observed compared to males (P = 0.028). Different daily activity patterns of the two sexes may explain this observation. The study of variation in social structure of wild Equids will enhance our understanding of the evolution of social systems in domestic horses and will improve the design of their boarding conditions (e.g., in better design of “Paddock Paradise”). Wild Asses that were reintroduced in the Negev Desert about 20 yrs ago show a social structure compatible with fission-fusion of groups. The ratio between juveniles and females did not change from an earlier study, soon after the release. Females were observed near the water source less frequently than males, possibly due to different activity patterns. The study of variation in social structure of wild equids will improve the design of boarding conditions for domestic horses.