Copulatory behavior in a free-ranging population of stumptail macaques (Macaca arctoides) in Mexico

Mating and Reproductive Success in Free-Ranging Stump-Tailed Macaques: Effectiveness of Male–Male Coalition Formation as a Reproductive Strategy

Male coalition-like formation, recently found in stump-tailed macaques (Macaca arctoides), occurs when several top-ranking males collaboratively guard females to prevent mating with other rival males and actively share secured mating opportunities with their allies. We lack a comprehensive understanding of the proximate mechanisms underlying such male coalitions, e.g., the effect of genetic relatedness. Such cooperative partner choice among males is particularly interesting in animals, such as M. arctoides, that live in matrilineal (female philopatry/male dispersal) society. Theoretically, in such a social system, females, and not males, are often related to each other by kinship. Thus, the occurrence of cooperative behavior between related females are generally common, but it would be rare between unrelated/non-kin males in such matrilineal society. Herein, for the first time, we report detailed copulatory behaviors, including mating and reproductive success, in relation to male coalition-like formation in free-ranging M. arctoides following direct behavioral observation and genetic analysis. We found that coalition-forming male–male alliances often occur among both individuals that are highly related and those that are less related. We identified two groups with different mating strategies, i.e., single-male monopoly and coalition-male monopoly groups. In both groups, nearly 80% of copulations were monopolized by a single male or by coalition males. However, the single-male monopoly strategy allows opportunistic/sneaky copulations by other males with a relatively high probability. Thus, the degree of reproductive success did not reflect mating success. In contrast, the males employing a coalition strategy successfully shared their mating and reproductive success, particularly in the largest group. Compared with single-male monopolized groups, the coalition-male monopoly groups copulated with a considerably more number of females, suggesting that coalition males can effectively guard against opportunistic/sneaky copulation by rival males. We also found that coalition-forming male–male alliances often occur regardless of the degree of kinship/relatedness, indicating the complexity and flexibility inherent in the male social bond of M. arctoides.

Tactical deception in sociosexual behaviour of stump-tailed macaques (Macaca arctoides): an exploratory study

Tactical deception (TD) is a social strategy in which a subject performs an action to its own benefit causing disadvantage for a competitor. In primates, the cognitive mechanisms involved in TD have been described at different levels. Sneaky mating is a common context within which to study TD because in many primate groups, dominant males monopolize access to females and subordinate males must find a way to copulate with females avoiding the alpha’s presence. The objective of this study was to explore which of the TD behavioural strategies are involved in the male sociosexual behaviour of a group of stump-tailed macaques (Macaca arctoides). We found that the subordinate males participated in more interactions when they were in a section of the enclosure where the alpha male was not present. The alpha male had more copulation interactions, but the beta male’s interactions lasted longer on average. Our data offer evidence in support of the hypothesis that stump-tailed macaques may use TD strategies that are related to operant conditioning.

Visitor effect on the behavior of a group of spider monkeys (Ateles geoffroyi) maintained at an island in Lake Catemaco, Veracruz/Mexico

We analyzed the effect of human visitors on the behavior of a group of spider monkeys (Ateles geoffroyi) kept on a small tourist island. Although the spider monkey is a common species in zoos, there are very few specific studies on visitor effects on these monkeys. We conducted behavioral observations on the group of spider monkeys to evaluate the effect of visitors. We also used actimetry devices to measure the variations in the spider monkeys' locomotor activity associated with human presence. With regard to the effect on behavior, we found an increase in self-directed behaviors and a decrease in vocalization, both associated with human presence. Moreover, our results suggest that when people feed monkeys, there is an increase in agonistic behaviors. On the other hand, we found that changes in activity levels in response to human presence vary among individuals. We conclude that changes in spider monkeys' behavior could provide evidence of the negative effect of visitors in our study conditions. Although we discuss the differences in activity levels due to differences in social position, further research is required this topic. Our results can be used to inform management plans for this species in captivity. Improving this relationship between humans and non-human primates through tourism education programs would benefit ecotourism and therefore species conservation programs.