Sex differences in leadership during group movement in mantled howler monkeys (Alouatta palliata)

Abstract

Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group‐defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys.

Variation in personality can substitute for social feedback in coordinated animal movements

“…In our model, these effects were an emergent property of variation in a single personality characteristic. This characteristic could represent various behavioural traits, such as boldness 27 , motivational state 29,30 , social status 53 or even vocalisation intensity 82,83 and as such, our findings may be applicable to a broad range of group-living organisms. Future studies could explore the influence of additional personality parameters, as this may lead to synergistic or stabilising effects resulting in more complex group-level responses.…”

“…1). This kind of decision process has been observed in fish 45,46 , birds 47 and mammals, including primates 9,30,38,48 , cattle 49,50 and Prezwalski horses 51 .…”

“…While not without controversy (e.g., 22 ), we use the term 'personality' here for reasons of word economy, to describe consistent individual variation in behaviour between individuals in a group, regardless of underlying cause of the variability. The available data indicate that the distribution of personality in a group can influence the outcome of various collective actions 18,[23][24][25][26][27][28][29][30][31] . For example, colonies of honeybees containing behaviourally more diverse individuals are collectively more successful foragers than less diverse colonies 13 and groups with different mixed composition of shy/ bold or social/asocial animals perform better than homogeneous groups in various taxa [31][32][33] .…”

Female reproductive energetics in mantled howler monkeys (Alouatta palliata): A follow‐up study

“…Given that female mantled howler monkeys do not seem to compete directly for food, which in other species underlies variation in energetic condition (Bergstrom et al, 2020; Rosetta et al, 2011), it is unlikely that the high C‐peptide concentrations of gestating females result from priority of access to food. However, females are more likely to lead group movements toward feeding trees when gestating than at other reproductive states (Ceccarelli et al, 2020). This raises the intriguing possibility that, as observed in other primate females (e.g., Cebus capucinus : Boinski, 1993; Propithecus and Eulemur : Erhart & Overdorff, 1999), leadership could yield foraging advantages that improve energetic condition.…”

Evaluating extinction debt in fragmented forests: the rapid recovery of a critically endangered primate

“…For this, we payed special attention to group travelling instances. These allow for the detection of individuals that may be in the periphery of the group, as howler monkeys are group living and show conspicuous and relatively cohesive group movement patterns (Van Belle et al ., 2013; Ceccarelli et al ., 2020). Typically, we would spend a complete day (never less) with each study group, but if required, and particularly with larger groups and/or if less than two travelling instances were observed, we spent additional days observing them.…”