Bourjade, M., Thierry, B., Maumy, M., & Petit, O. (2009). Decision-making in Przewalski horses (Equus ferus przewalskii) is driven by the ecological contexts of collective movements. Ethology, 115(4), 321–330.
Abstract: We addressed decision-making processes in the collective movements of
two groups of Przewalski horses (Equus ferus przewalskii) living in a semi
free-ranging population. We investigated whether different patterns of
group movement are related to certain ecological contexts (habitat use
and group activity) and analysed the possible decision-making processes
involved. We found two distinct patterns; ‘single-bout’ and ‘multiplebout’
movements occurred in both study groups. The movements were
defined by the occurrence of collective stops between bouts and differed
by their duration, distance covered and ecological context. For both
movements, we found that a preliminary period involving several horses
occurred before departure. In single-bout movements, all group members
rapidly joined the first moving horse, independently of the preliminary
period. In multiple-bout movements, however, the joining
process was longer; in particular when the number of decision-makers
and their pre-departure behaviour before departure increased. Multiplebout
movements were more often used by horses to switch habitats and
activities. This observation demonstrates that the horses need more time
to resolve motivational conflicts before these departures. We conclude
that decision-making in Przewalski horses is based on a shared consensus
process driven by ecological determinants.
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Jacobs, A., Maumy, M., & Petit, O. (2008). The influence of social organisation on leadership in brown lemurs (Eulemur fulvus fulvus) in a controlled environment. Behav. Process., 79(2), 111–113.
Abstract: Studies on leadership during group movements in several lemur species showed that females were responsible for the travelling choices concerning time and direction. Interestingly, in these species females are dominant over males. We investigated the influence of social organisation upon leadership processes by studying a lemur species in which social organisation is characterized by the absence of female dominance: the brown lemur (Eulemur fulvus fulvus). The study was conducted on a semi-free ranging group of 11 individuals and the analysis performed on 69 group movements showed that all the individuals could initiate a group movement. In 34 cases, the whole group moved. There was no significant difference in the number of start attempts or in the number of group members involved from one initiator to another. Moreover, there was no effect of sex or age of the initiator on the number of individuals following it or on the speed of the joining process. Therefore, the leadership observed is widely distributed to all group members. These results support the hypothesis of an influence of social organisation upon the decision-making processes but still remain to be studied in a more relevant ecological context.
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