Abstract: In the present study, we sought to determine the influence of stress and temperament on working memory for disappearing food in horses. After assessment of five dimensions of temperament, we tested working memory of horses using a delayed-response task requiring a choice between two food locations. Delays ranging from 0 to 20 s were tested. The duration of working memory for disappearing food was first characterized without stressors (N = 26). The horses were then divided into two groups and their performance was assessed under stressful (exposure to acute stressors prior to testing, N = 12) or control conditions (N = 12). Results showed that the duration of working memory for disappearing food lasted at least 20 s under nonstressful conditions, and that under stressful conditions this duration lasted less than 12 s. This stress-induced impairment confirms in a nonrodent species that working memory performance is very sensitive to exposure to stressors. In addition, working memory performance in horses is influenced by the temperamental dimension of fearfulness according to the state of stress: fearful horses showed better performance under control conditions and worse performance under stressful conditions than nonfearful horses. These findings are discussed in the context of the Yerkes–Dodson law of stress and performance.

Abstract: A harem of takhi (Equus ferus przewalskii) was observed during introduction to the Hustain Nuruu Steppe Reserve of Mongolia. The goals were to examine whether the harem exhibited significant behavioural synchrony, whether release had an effect on time budget, and what the implications might be regarding acclimatisation to the wild. Behaviours were scan sampled every 10 min between the hours of 06:00 and 22:00, twice before release, twice immediately after release, and twice 2 years after reintroduction. Time budgets were constructed from these data. Considerable behavioural synchrony was evidenced both before and after release. Crepuscular grazing and midday resting were typical, regardless of the date relative to release. Upon release, the amount of time spent moving doubled for all age classes. It is suggested that this increase resulted from exploration. The amount of time spent grazing and standing remained unchanged; the increased amount of time spent moving came at the expense of resting. Two years later, the horses still spent more time moving than when captive. Somewhat less time was spent grazing, although the difference was not significant. More time was spent resting in 1996 than immediately after release. These time budgets provide evidence of successful acclimatisation to the wild. Trekking between favoured sites could account for the persistent increase in time spent moving, with concomitantly less time needed to meet nutritional needs by grazing and more time available for resting. Housing captive takhi in large enclosures is evidently insufficient to permit the amount of movement exhibited by this wild harem. The time budget of the 1- and 2-year olds was more similar to that of adults than foals, indicating approaching adulthood. That 1- and 2-year olds were nursed, without loss of body condition by the dam, provided additional evidence that the takhi achieved excellent nutritional status in the wild.

Abstract: Feral asses were studied on Volcano Alcedo, Galapagos Islands, Ecuador, during the wet season of 1980. On the volcano rim during March/April, two stable groups were observed to have a `female (harem) defense' polygynous mating system [Emlen, S.T., Oring, S.W., 1977. Ecology, sexual selection, and the evolution of mating systems. Science 197 (4300), pp. 215-223] and social behavior patterns and feeding ecology similar to feral asses living in a habitat where forage and climate are similar, e.g., Ossabaw Island, Georgia [Moehlman, P.D., 1979. Behavior and ecology of feral asses (Equus asinus). Nat. Geogr. Soc. Res. Rep., 1970, pp. 405-411; Moehlman, P.D., 1997. Feral asses (Equus africanus): intraspecific variation in social organization in arid and mesic habitats. J. Appl. Anim. Behav. Sci., this issue; McCort, W.D., 1980. The feral asses (Equus asinus) of Ossabaw Island, Georgia., PhD Dissertation, Pennsylvania State University, University Park, 219 pp.].

Abstract: The behavior of feral populations of the African wild ass (Equus africanus) were studied in the Northern Panamint Range of Death Valley National Monument for 20 months from 1970 to 1973 [Moehlman, P.D., 1974. Behavior and ecology of feral asses (Equus asinus). PhD dissertation, University of Wisconsin, Madison, 251 pp.; Moehlman, P.D., 1979. Behavior and ecology of feral asses (Equus asinus). Natl. Geogr. Soc. Res. Reports, 1970: 405-411]. Maintenance behavior is described and behavior sequences that were used in social interactions are quantified by sex and age class. Agonistic, sexual, and greeting behavior patterns are described and analyzed in conjunction with the responses they elicited. Mutual grooming mainly occurred between adult males, and between females and their offspring. Five types of vocalizations were distinguished: brays, grunts, growls, snorts, and whuffles. A second population was studied for 1 month on Ossabaw Island, GA (Moehlman, 1979). This population had more permanent social groups and had a higher rate of mutual grooming and foal social play.

Abstract: In animal groups, collective movements emerge from individual interactions. Biologists seek to identify how characteristics of actors in these groups, and their relationships, influence the decision-making process. We distinguished two basic factors determining leadership in group choices: identity and state. We hypothesized that identity is more important to leadership in groups with stable relationships, which permit the development of habitual roles. In groups with fluid membership, particular individuals or subgroups are less likely to emerge as consistent leaders. Instead, we predicted that movement initiation in unstable groups depends on individual state at the time of the decision. We characterized how identity and reproductive state influenced leadership patterns in the movements of plains zebra. As in many other mammals, lactation in this species significantly alters water and energy needs. We investigated leadership in tightly knit harems and loosely bonded herds of multiple harems. Harem females tended to have habitual roles in the initiation of harem movement. In herds, however, we found no consistent leaders among harems. At both levels of social organization, lactation was a key determinant of leadership. In harems, lactating females were more likely to initiate movement than nonlactating females. In turn, harems containing lactating females were more likely to lead herd movements. Thus, we conclude that social relationships and reproductive state together shape the interactions that produce group behaviours. One benefit to lactating females of leading herd movements is preferential access to scarce water. Thus, leadership roles in group decisions may have fitness consequences.