Cooperation and competition in wild male Barbary macaques (Macaca sylvanus) in Morocco

Content Provider	Semantic Scholar
Author	Young, Christopher
Copyright Year	2013
Abstract	Mammalian males compete for a non-sharable resource (receptive females) and are typically the dispersing sex, thus cooperation between males may appear counterintuitive. However, if both partners gain mutual benefits from cooperating, such as an increase in mating/reproductive success, then cooperation can become a feasible strategy. Coalitions can be opportunistic, in the short-term providing direct benefits or can function to increase rank positions and provide future reproductive payoffs. These coalition types are predicted to occur at different levels of within group contest potential predicted by the monopolization potential of the alpha male over access to receptive females. It has been suggested males must weigh-up the rank/strength of the potential allies and the target to recruit a partner who will provide enough combined intrinsic fighting ability to defeat the target. Alternatively, males may base partner recruitment decisions on past experiences with group members (attitudinal partner choice) and regularly recruit reliable partners. Coalitionary partner choice may be mediated via social bonds under such circumstances. The aim of this thesis was to shed light on male cooperation by examining male mating competition and social relationships and how these are influenced by coalitionary activity in a group living, wild, primate with male dispersal, the Barbary macaque (Macaca sylvanus). To this end I used a bottom-up approach, by examining the complete chain of events which led to male-male cooperation. I determined what males can ascertain about female reproductive state to gain an empirical estimate of mating contest potential within the groups. I utilised the Priority of Access model as a platform to investigate male mating competition and I examined the factors which led to deviation from the models predictions, namely female behaviour and male coalition formation. Species specific measures of male contest allowed for a critical evaluation of a mathematical model designed to predict different types of within group coalition formation (Pandit/van Schaik coalition model). Specifically, I examined how the model’s predictions fitted to empirical data across two species with variable contest potentials (Barbary and Assamese macaques, M. assamensis). Male social relationships were analysed to determine if Barbary macaque males formed long-term social relationships, even during intense periods of competition (mating seasons). Finally, male social bond strength was examined to identify if they provided an adaptive benefit in terms of cooperation through coalition formation or if coalition partners were selected by hierarchal status alone. Data were collected on two groups of wild Barbary macaques in the Middle Atlas Mountains, Morocco (Sept. 2009-Aug. 2011). I collected over 2,000 hours of behavioural focal observations on all male subjects in the two groups as well as ad libitum data and 549 coalition bouts were observed of various size and success. Additionally, 155 female faecal samples were analysed to assess dates of conception using enzyme immune assays of progestogen metabolites, as well as visual monitoring of female sexual swelling size to determine receptive synchrony. Analysis of female hormone concentrations revealed ovulation was most likely to occur during the maximum swelling period. However, male mating behaviour was further concentrated around the fertile phase implying that males infer information from more than swelling size alone. Male mating frequency increased in line with female socio-sexual behaviour. Most strikingly my results showed that males invested equally in mating during fertile and non-fertile, i.e. post-conception, maximum swelling phases. Despite these additional swelling periods reducing monopolisation potential of high ranked males mating was still skewed up the hierarchy but high ranked males did not gain as large a share as expected by the Priority of Access model. Females frequently initiated sexual encounters, predominantly with mid-ranked males, increasing their mating success while male coalitionary activity independently increased mating success. Frequent associations with females were costly to males as they were the targets of bridging coalitions, decreasing future mating opportunities for the targets. High-ranking males did not increase their mating success directly through bridging coalitions but acted to dilute the effects of female mating behaviour. Furthermore, Barbary macaque males formed long-term social bonds enduring through highly competitive mating seasons. Males who shared strong social bonds were more likely to be recruited as coalition partners suggesting that males use more than merely rank position of available partners when recruiting. Examination of the Pandit/van Schaik coalition model showed that at high contest potential opportunistic coalitions should be utilized to gain access to females monopolised by high ranked males. Whereas the empirical data did not match the predictions at mid-low contest potential where male affiliation may play a role in facilitating rank-changing coalitions which require reliable partners to defend higher rank positions once obtained. Thus, strong social bonds can provide both short- and long-term benefits by reducing the likelihood of partner defection during coalitions and providing a long-term partner to facilitate successful rank-changes and ultimately increase both status and mating/reproductive success. In sum, my thesis adds to the current literature on the links between male reproductive strategies, social bonding and cooperation in group living mammalian societies, with male dispersal. Through investigation of the complete chain of evidence from male contest competition to mating success and cooperation via male social bonding, this study united several previously separate pieces of research into one comprehensive picture and may provide a template for future research. Coalitionary activity can provide mutual benefits for both partners suggesting that cooperation may be based on previous affiliative interactions with group members brought about by attitudinal partner choice.
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://ediss.uni-goettingen.de/bitstream/handle/11858/00-1735-0000-0001-BBCB-E/PhD_Thesis%20_Chris_Young.pdf;sequence=1
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article