Social aging in male and female Barbary macaques

Abstract

Aging brings about notable changes in sociality, with an increasing focus on essential partners in both humans and nonhuman primates. Several studies have shown that older nonhuman primates have fewer social partners and shift their types of interactions. The majority of these studies, however, involved only female individuals.Much less is known about the trajectory of social aging in males. We collected 2180 h of focal observation data in a large age-heterogeneous sample of 34 male and 50 female Barbary macaques (Macaca sylvanus; age range 5-30 years) living in two social groups at the outdoor enclosure at La Forêt des Singes in Rocamadour (France). To track age-related changes in social engagement of both sexes, we used classical behavioral and social network analysis to measure age-related variation in the number of partners, the frequency of affiliative interactions, and the position in the social network (eigenvector centrality and local clustering coefficient). We found that females were more central in most social network metrics than males, that is, had more social partners and were more engaged in affiliative interactions than males. We did not find notable sex differences with age: both sexes showed a similar decline in social activity and energy-demanding activities like jumping or running.Our results thereby extend our knowledge of older nonhuman primates' social life and emphasize that age can have a similar impact on female and male social behavior.

Ageing red deer alter their spatial behaviour and become less social

“…Investigating demographic structuring, selective disappearance, and spatial behaviours in primate populations (e.g. 12,27,43 ) may shed an important light on the different drivers of age-related changes in sociality across mammals and other taxa. Ultimately, broadening the selection of study organisms for age-sociality interactions to include those a wider variety of fluid and rigid social systems could help to develop generalisable insights about the causes and consequences of social ageing across the tree of life.…”

“…For example, if an animal forms relationships when it is young which are not replaced when those contacts die 25,26 , then older animals will be less socially connected as a result. Social connectedness has recently been shown to correlate with age in chimpanzees, macaques, ibex, and marmots 12,[27][28][29][30] , but the relative roles of these spatial, demographic, and withinindividual drivers have yet to be investigated. Untangling these processes could shed a light on the relative importance of within-individual age-related behavioural changes (compared to physiological or demographic processes) in determining population structure in wild animals.…”

Social ageing: exploring the drivers of late-life changes in social behaviour in mammals

“…Physical deterioration is expected to lead to declines in capacity to socially interact and reduced desirability as a social partner, leading to overall declines in social connectedness due to both social withdrawal and social exclusion. [16,35,56,57] §2a(ii) energetic deficiencies Energetic deficiencies are expected to restrict an individual's movement and therefore their ability to socially engage or the likelihood of others coming into social contact, leading to reductions in the quality and quantity of social relationships. [16,35,56,57] §2a(iii) sociocognitive decline Socio-cognitive decline may facilitate reduced social engagement owing to decreased social motivation, social attention, or inability to recognize partners.…”

“…[16,35,56,57] §2a(ii) energetic deficiencies Energetic deficiencies are expected to restrict an individual's movement and therefore their ability to socially engage or the likelihood of others coming into social contact, leading to reductions in the quality and quantity of social relationships. [16,35,56,57] §2a(iii) sociocognitive decline Socio-cognitive decline may facilitate reduced social engagement owing to decreased social motivation, social attention, or inability to recognize partners. Old individuals may be less desirable partners as a result.…”

Age-related change in adult chimpanzee social network integration

“…High measures of centrality derive from an individual's many and strong social ties and those of their direct contacts (Sosa et al, 2020). In non-human animals, centrality corresponds with greater food discovery (Paridae songbirds, Aplin et al, 2012), and has been shown to decrease with age in female yellow-bellied marmots (Blumstein et al, 2018), and in some primates (Barbary macaques, Rathke & Fischer, 2021) but not all those examined (rhesus macaques, Liao et al, 2018). In some species, embeddedness corresponds with decreased parasites and infection (Balasubramaniam et al, 2016;Duboscq et al, 2016), however, under some circumstances it can lead to greater pathogen exposure (Nunn, 2012;Page et al, 2017).…”