Abstract: A behavioural study of feral horses was conducted on the Pryor Mountain Wild Horse Range in the western United States. All 270 horses on the Range were identified individually. The sex ratio was nearly balanced. Foal to adult female ratio was 43-2:100. Morality was concentrated among foals and old horses. Horses were organized as forty-four harem groups each with a dominant stallion, one to two immature stallions, one to three immature mares, one to three adult mares and their yearling and foal offspring, and 23 bachelor groups of one to eight stallions. Harem groups were quite stable year-round because of dominance and leadership by the stallions and group fidelity by mares and their offsring. Most changes occurred during the breeding season and involved immature females. Defeat of dominant stallions was infrequent. Immature males were tolerated because of their submissive behaviour. Bachelor stallion groups were inherently unstable. Mares came into heat after foaling in May/June, and were mated by harem stallions only.

Abstract: In many animal groups, certain individuals consistently appear at the forefront of coordinated movements [1-4]. How such leaders emerge is poorly understood [5, 6]. Here, we show that in pairs of sticklebacks, Gasterosteus aculeatus, leadership arises from individual differences in the way that fish respond to their partner's movements. Having first established that individuals differed in their propensity to leave cover in order to look for food, we randomly paired fish of varying boldness, and we used a Markov Chain model to infer the individual rules underlying their joint behavior. Both fish in a pair responded to each other's movements-each was more likely to leave cover if the other was already out and to return if the other had already returned. However, we found that bolder individuals displayed greater initiative and were less responsive to their partners, whereas shyer individuals displayed less initiative but followed their partners more faithfully; they also, as followers, elicited greater leadership tendencies in their bold partners. We conclude that leadership in this case is reinforced by positive social feedback.

Abstract: The mechanisms of activity synchronization in group living ungulates are not well understood. In a case study on herd of 15 Gasconne beef cows with calves observed during a total of 25 summer daylight periods in 2004 and 2005, we examined whether cows similar to each other in body weight or in reproductive status were more synchronized and whether the timing of activity switches were determined by specific leading animals. We calculated the synchronization of all possible pairs of cows in the herd and tested the effects of similarity in body weight and in reproductive status (lactating versus non-lactating) on synchronization in the pair. Further, we assessed whether any specific individuals, and especially the dominant cows, were more able, through their own activity switch, to incite another cow to follow shortly with her switch in activity. We found that body weight differences had a negative influence on pair synchronization (GLMM, F1,65 = 6.79; p < 0.05), but reproductive status did not affect the synchronization. Cows' individual identity explained only a small proportion (<2%) of variability in intervals between switches of subsequent cows. Furthermore, dominance status of an individual cow did not correlate with mean interval between her activity switches and activity switches of the next cow (lying down: Spearman correlation, rs = -0.16, n = 14, p > 0.10; standing up: Spearman correlation, rs = -0.38, n = 14, p > 0.10), indicating that there were no leading animals initiating switches in activity in our herd.

Abstract: To benefit from group living, group members need to keep the group cohesive by coordinating time and direction of travelling. Self-organization and leadership are two means of coordination and two types of decision can be made on the group level: combined and consensus. We studied the initiation process of group movements during the morning departure of a group of chacma baboons, Papio hamadryas ursinus, from its sleeping site in De Hoop Nature Reserve, South Africa. Findings from other female-bonded primate groups led us to hypothesize that females should play a major role in the decision-making process. Approximately 75% of the adults made a start attempt, with 62 of 92 attempts being by males. There was no sex difference in the probability of being successful when initiating an attempt. Lactating females initiated fewer than pregnant or cycling females. Thus, at least for this group of chacma baboons, leadership appeared to be distributed and the decision about the timing of departure and travel direction seemed to be a partially shared consensus decision with adult males contributing more to the decision outcome, with a slightly more prominent role of the dominant male. Our results do not support the [`]leading females' hypothesis. No behavioural patterns that might serve as specialized signals leading to a more successful recruitment of other group members were observed. The departure process appeared to be coordinated merely through individuals setting an example by moving off.