Sexual segregation in fallow deer: are mixed-sex groups especially unstable because of asynchrony between the sexes?

Abstract

In gregarious ruminants, females and males tend to live in separate groups outside the rutting season. According to the 'activity budget' hypothesis, this is due to an activity asynchrony between the two sexes reducing the lifetime of mixed-sex groups. We tested this hypothesis in a fallow deer population. Activity asynchrony was more frequent in mixed-sex than in single-sex groups. In addition, mixed-sex groups had a higher probability of splitting-up than all-female groups, and they mainly split up into singlesex groups. However, activity asynchrony did not appear as a major cause of splitting-up.

Behavioural synchrony between fallow deer Dama dama is related to spatial proximity

“…1). In another study of fallow deer recording the proportion of time mixed-or single-sex groups were completely synchronous or not, Villerette et al [42] recorded that allfemale groups were highly synchronous, and conformed totally within the group for 93.1% of the time. This value falls in the same region as the synchrony seen in the current study between the focal and its close neighbours, but is a little high when considering the action of a randomly selected control, which is likely to be due to differences in measurement criteria and definitions of group membership.…”

“…Using the strict descriptions of instantaneous observed behaviour described in Table 1 may falsely classify animals that are conducting synchronised behaviours that are masked by transient additional behaviours (so, in our classification an animal that is resting but vigilant is classified as conducting a different behaviour to one that is resting and chewing). To avoid these fine-scale mistakes, we also categorised the data into a dichotomous descriptor 'inactive' (when the deer were lying on the ground) or 'active' (all other activities; Table 1), following a system previously used for both fallow deer [42] and red deer [10]. We calculated the number of times the first-, second-and third-closest neighbour and the control individual were active or inactive at the same time as the focal individual for each fifteen-minute observation sample (note that proportions are used for plotting the figure).…”

Behavioural synchronization from an ethological perspective: Overview of its adaptive value

“…from lying to standing or the reverse) synchronously with other group members (Stoye, Porter, & Stamp Dawkins, 2012). In fallow deer ( Dama dama ), due to the social affinities hypothesis (males and females differing in their behaviour and motivation; Bon, 1992; Michelena et al, 2004) and to the activity budget hypothesis (males and females differing in the time they need for different activities; Conradt, 1998; Neuhaus & Ruckstuhl, 2004; Ruckstuhl, 1998), social cohesion between males and females appears to be correlated with a higher degree of activity synchrony in unisex groups compare to mix-sex groups (Villerette, Helder, Angibault, Cargnelutti, & Gerard, 2006).…”