The effects of alpha male removal on the social behavior of a group of olive baboons: Females seem to respond to male removal showing a more affiliative and tolerant behavior

The effects of alpha male removal on the social behavior of a group of olive baboons (Papio anubis). Ester Orient & Federico Guillén-Salazar. Journal of Applied Animal Welfare Science, Aug 26 2021. https://doi.org/10.1080/10888705.2021.1968401

Abstract: In captivity, the managers of primate populations have removed individuals from their groups for medical and social reasons, but there has been little documentation regarding the consequences of this extraction on the sociality of the remaining individuals. This study provides information about the social effect of the alpha male removal in a group of olive baboons (Papio anubis) maintained at the Station of Primatology of CNRS (France). Data on social behavior was collected before and after male removal and then compared. Moreover, this social information was used to calculate the individual dominance index and the group dominance ranking. Overall, our results indicate that females seem to respond to male removal showing a more affiliative and tolerant behavior. However, the results also highlight the different coping mechanisms of females with this new social context. Therefore, this information could be useful for managers of primate populations, allowing them to anticipate the response of captive groups when facing certain sociodemographic changes. In this regard, we recommended creating a detailed procedure before the removal of the individuals that considers the characteristics of the individuals.

KEYWORDS: Male removalolive baboon (Papio anubis)small groupssocial behavior

Discussion

The results presented here show how after male removal half of the dyads increased their grooming. Moreover, the females displayed a less aggressive behavior in general terms, especially to one of the most subordinate females, and a more tolerant behavior toward the most dominant female (decreas^Bing their retreats). The social scenario after male removal therefore seems to be close to a peaceful scenario, in which females try to increase the strength of their social bonds.

The increase of the affiliative interactions observed in females are consistent with the results obtained by Chowdhury and Swedell (2017) after the male’s death in a group of chacma baboons.

However, while these authors observed that all females invested more time in grooming, we only observed the increase of the interactions in half of them. In this sense, Chism & Rogers (2002) suggest that the removal of individuals may be disruptive to the relationships of certain animals, but not in others, as observed in this study. They also claim that interactions are established between real individuals, with their own characteristics (e.g., personality, experience) and not between theoretical categories of individuals.  Our results partially agree with the description made by authors such as Keddy-Hector and Raleigh (1992) or Lemasson et al. (2005) after alpha removals, because they state that the remaining individuals increase both affiliative and aggressive interactions but, in this study, females only increased their grooming exchanges. Moreover, our results are totally opposite to those obtained by other authors who pointed out that animals become more aggressive after the removal of the alpha individual (Lowland gorilla: Hoff et al., 1982; Rhesus macaques: Judge et al., 1995; Common marmosets: Lazaro-Perea et al., 2000). As indicated previously, our females showed a more tolerant behavior after male removal, decreasing their mutual aggressions and their avoidance of the more dominant female.

Changes in the dominance hierarchy are a common outcome of the modification of the socio-demographic composition of a group [Japanese macaques (Macaca fuscatta): (Kawai, 1960; Nakamichi et al., 1995); Rhesus macaques: (Bernstein, 1964); Vervet monkeys: (Guy & Curnoe, 2011)]. After a social and demographic change, the remaining individuals try to cope with this period of social instability by re-organizing their previous relationships (Colmenares & Gomendio, 1988), which may result in a change dominance ranking. In this work, there has been a slight change in the female dominance ranking after the male removal, particularly in regard to the two females located in lower positions. This change in the agonistic behavior of these females leads to a partial modification in the dominance ranking. Therefore, our results agree partially with the idea of a social reorganization after a period of instability, stated by Colmenares and Gomendio (1988).

As pointed out by Lemasson et al. (2005), the social status of individuals and the species are determining factors in the effects of the removal of an individual. We suggest that the changes observed in female behavior could be mainly due to the absence of the male, the most dominant individual in the group. These female behavioral adjustments are in line with statements from Packer and Pusey (1979) and Dunbar (2013) regarding the lack of female control over males in the baboon genus. The big size of male olive baboons, compared to their female counterpart, seems to provide the male with some degree of influence over female behavior and, consequently, over their sociality. Nevertheless, it should be noted, that despite the possibility that males exercise a certain influence over females, the alpha male of the study seemed to have established a “friendly relationship” with the most dominant female. Strum (1974) defined this type of relationship between males and females as a typical trait of the natural behavior of male baboons. Therefore, the identification of the typical traits of baboons’ natural behavior could be used as an important indicator of animal welfare. In addition, the dominance ranking obtained before male removal and the changes observed in the females’ social behavior after male removal reinforce the idea of a male influence over females.

Unfortunately and, despite the fact that female social interactions varied after male removal, our comparisons are not statistically significative. The small size of the study group, the variability of female dyadic interactions, and the short post-removal period of observation could limit our results and its later interpretations. In this regard, it would have been interesting to increase the information about the sociality of the study group with data regarding the social behavior of young females.  However, the initial procedure designed to study the group sociality in depth, did not contemplate collecting data on the social behavior of young females. Moreover, we assume that dyads respond differently to the demographic changes and that a longer period of post-removal observation could allow us to observe an evolution of the female relationships different from that observed [e.g., the development of stronger and affiliative social relationships observed by Schel et al. (2013) in chimpanzees, one year after modifying the demographic composition of the study group].

This study may be interesting from an applied standpoint, because it shows how the description of the social behavior before and after the removal of an individual from a social group, and their later comparison, can be useful for primate managers to anticipate the behavioral response of animals when facing future modifications of the group sociodemographics. In this sense, some authors (Coe, 1993; Raleigh, McGuire, Brammer, & Yuwiler, 1984; Steklis, Raleigh, Kling, & Tachiki, 1986) have stated that those events that modify the social bonds and the dominance relationships of a group may lead to behavioral and physiological signs of distress for a long time afterward. Our results show how, after male removal, females seem to cope with this social instability by creating a more peaceful scenario. Their sociality does not seem to be negatively affected in the short term by this change. Moreover, our findings confirm that factors such as the social status, the species, and the individual’s characteristics, should be considered when planning the removal of an individual from a social group of primates. We recommend elaborating an accurate plan for the individual’s removal prior to carrying it out. This plan must collect both the knowledge acquired by animal care staff over the years and that obtained through scientific studies such as ours. As a whole, the information here presented ads to the scarce literature surrounding alpha male removal in small groups of primates.