This entry was written by Dean Rub as part of a project done in BIAN 6133 ‘Human Reproductive
Strategies’ at The Australian National University in 2019 Semester 2.
Introduction
Evolutionary explanations for why nonhuman primates choose their mates, are attributed through studying the behavioral complex’s within primate societies. This is due to primates being pre-dominantly social based animals. Understanding the structure of these social societies brings forth better evaluation of the behaviors that attribute to these forms of selection. This in turn, enables evolutionary biologists the ability to bring forth hypothesis’s to how mate choice occurs. The following entry looks into three key components within nonhuman primate mate choice and aims to understand and explain the evolutionary reasoning behind them. These components include social rank and how it influences chances of reproducing (Widdig et al, 2004). Inbreeding avoidance which intern is leading female dispersal (Walker et al, 2017). Mate Guarding, a defensive mechanism to strengthen one’s reproductive success (Setchell and Wickings, 2006).
In this entry, I’ll be evaluating the literature and bringing forth discussion in context of the evolutionary explanations behind these three key components, that influence nonhuman primates mate choice.
Main Text
Social Rank
When looking into mating success and social rank, firstly we must assess whether physical preference of health is related to the mate choice itself. Georgiev et al (2015) investigated the quality of health and rank within Rhesus Macaques (Macaca. mulatta) males, and their level of mating success. What they found was that generally higher-ranking males had better quality health then lower ranking males. Health and rank status coincided with each other to higher levels of mating and reproductive success, compared to lower ranking and individuals with poorer health having lower levels of reproductive success (Gerogiev et al, 2015). This pushing forth the evolutionary concept that social rank and health attributes to the reproductive success of male M. mulatta.
When looking at nonhuman primate species in context of mate choice, one important factor is the influence of social rank. Widdig et al (2004) investigated the reproductive skew within M. mulatta. What they found was 24% of infants sired, was from one individual male. 71% of the troop’s males, didn’t reproduce annually and 74% of males had at least one-half paternal sibling within their birthing unit. Furthermore, male reproductive success was heavily linked to high ranking males aged 9-11, and whom spent majority of the mating season around the females within the troop (Widdig et al, 2004). As primates live a quite socially complex life’s, social factors like rank heavily influence a female’s mate choice, this can be interpreted as evolutionary explanation for quality of the mate choice.
Chimpanzees (Pan troglodytes) have diverse population numbers, but predominantly live in large social hierarchical systems. These large social hierarchies are led by a male dominance ranking coalitions. Feldblum et al (2014) investigated coercive behaviors and the level of paternity. Interestingly what they uncovered was that there had been a strong correlation of aggressive behaviors, particularly from high ranking individuals that coincided with high levels of paternity. This had also been demonstrated in lower rankings males, although paternity had been dominated by higher rankings P. troglodytes (Fledblum et al, 2014). This pushing forth an evolutionary explanation that aggression and social rank correspond with the level of reproductive success in male P. troglodytes achieve.
Inbreeding Avoidance
P. troglodytes males are the philopatric sex within the species. This making P. troglodytes a valued study component for inbreeding avoidance. Walker et al (2017) investigated dissimilar breeding in P. troglodytes. What they found was since females are the dispersing sex, it enabled gene flow into the hierarchy. This dispersal is an important avoidance mechanism for the occurrence of inbreeding. Furthermore, natal females although similar to their fellow males, demonstrated to not be closely related to the males whom sired their offspring. Moreover, females across the study period had been less related to their sires, compared to non-sires (Walker et al, 2017). This showing that the dispersal of female P. troglodytes has in evolutionary influence for deterrence of inbreeding within P. troglodyte’s society.
Supporting evidence for the of dispersing females and its importance for inbreeding avoidance further evaluated in in Van Hooff et al (2005) investigation of Thomas Langurs (Presbytis thomasi). What they found was the dispersing of null parous females only occurred when their father became the leading resident of the community. This showed to be a biological response to seek mates elsewhere to reduce the prevalence of inbreeding. They also noted that parous females choose to flee to younger male groups, whom provided better offspring, louder vocal calls and general protection, which indicated a higher quality of mate choice (Van hoof et al, 2005). These patterns that are being demonstrated across nonhuman primate species, enables the notion that inbreeding avoidance and dispersal can be utilized as an evolutionary explanation for drastic mate choices within females.
Mate Guarding
Mate choice is more commonly seen within females, although male mate choice can be quite selective and expressed in defensive behaviors. Setchell and Wickings (2006) field study looked at mate choice within male Mandrills (Mandrills sphinx). What they uncovered was peri-ovulatory and high rankings status’s, influenced the level of mate guarding a female, moreover, the alpha male contributed to 98% of the mate guarding for the peri-ovulatory females. Furthermore, the degree of relatedness wasn’t an influencing factor for the level of mate guarding. This is a form of male sexual selection to maximize the male’s chances of reproductive success and to decrease the probability of post copulatory sexual selection (Setchell and Wikicking, 2006). This brings forth the evolutionary explanation on how male defensive behaviors are utilized in mate choice to maximize reproductive success.
Further field studies have shown presences of male mate guarding being expressed within Black Howler Monkeys (Aloautta pigra). Belle et al (2009) investigated male mate guarding and female mate choice in A. pigra. What they had found was females sexually presented to dominate males a lot more frequently than subordinate males. Moreover, Aplha males had been seen majority of the time within close proximity of the females, with regular sniffing of the genitals occurring, which suggest that mate guarding cost a lot of time and energy. Although females sexually presented towards Apha males more, subordinate males monopolized on the act more frequently when presented. This enabling the notion that subordinate males have less reproductive opportunity then alpha males, thus acting on sexual opportunities maximizes their fitness (Belle et al, 2009). The evolutionary reasoning behind mate guarding, is that nonhuman primates utilize more energy and time into reproductive protection, to maximize reproductive fitness.
The expression of mate guarding, particularly in peak mating season, can be considered a timely matter. The following field investigation from Girard-Buttoz et al (2014) looked into the feeding activity of long tailed macaques (Macaca facicularis). What they found was that the expression of mate guarding led to a decrease in time spent feeding and the overall consumption of food. This prompting that less energy was consumed during peak season. What they also noted was locomotion had declined during the expression of mate guarding, although the alpha male whom mate guarded during peak season, by the end of the season had a decline in body condition (Girard-Buttoz et al, 2014). The act of guarding as stated decreased the individuals feeding time, although this is a cost, the cost had been outweighed with the protection of one’s reproductive fitness, thus prompting the evolutionary reason behind this behavior.
Conclusion
The three important components unpacked within this entry gave some evolutionary explanations to why some of these nonhuman primate behaviors influence mate choice. Social rank showed that generally in two primate species M. mulatta and P. troglodytes impacted many aspects of life, which in turn influenced one’s level of mate choice. This attributes to some of the evolutionary reasoning behind why some of these sexual behaviors are apparent. Inbreeding avoidance showed the evolutionary reasoning behind why certain sex’s in a species disperse. In our case we looked at how P. troglodytes and P. thomasi dispersal. P. troglodytes inbreeding avoidance attributed to the gene flow into different hierarchies and avoidance in mating with similar mates. P. thomasi dispersed when females’ fathers took over the troop. This coincided with females seeking new younger mates within different troop societies, to avoid any inbreeding occurrences. Mate guarding is a form of defensive mate choice. We reviewed literature on three species of nonhuman primates in regard to mate guarding in this entry, M. facicularis, A.pigra and M. spinhx. M. facicularis showed a decrease in time feeding when mate guarding. M. spinhx showed high ranking individuals had been linked to high levels of mate guarding and reproductive success during periods of peri-ovulatory females’ presences. A. pigra alpha males spent majority of their time guarding females, although when females presented to subordinate males on rare occasion, they monopolized on it. As mate guarding is a defensive behavior for predominately male fitness, this gives some explanation in context to evolution for why this behavior occurs. Further investigations of nonhuman primate societies will bring forth a more knowledgeable approach to conducting behavioral assessments within context of these three important components, that aid in evolutionary biologists understanding of why nonhuman primates choose their mates.
Literature Cited
Belle, S. V., Estrada, A., Ziegler, T. E., & Strier, K. B. (2009). Sexual behavior across ovarian cycles in wild black howler monkeys (Alouatta pigra): male mate guarding and female mate choice. American Journal of Primatology, 71(2), 153–164.
Feldblum, J. T., Wroblewski, E. E., Rudicell, R. S., Hahn, B. H., Paiva, T., Cetinkaya-Rundel, M., … Gilby, I. C. (2014). Sexually Coercive Male Chimpanzees Sire More Offspring. Current Biology, 24(23), 2855–2860. doi: 10.1016/j.cub.2014.10.039
Hooff, J. A. V., Willems, E. P., Wich, S. A. (2005). Female dispersal, inbreeding avoidance and mate choice in Thomas langurs (Presbytis thomasi). Behaviour, 142(7), 845–868.
Georgiev, A. V., Muehlenbein, M. P., Prall, S. P., Thompson, M. E., & Maestripieri, D. (2015). Male quality, dominance rank, and mating success in free-ranging rhesus macaques. Behavioral Ecology, 26(3), 763–772.
Girard-Buttoz, C., Heistermann, M., Rahmi, E. (2014). Mate-guarding constrains feeding activity but not energetic status of wild male long-tailed macaques (Macaca fascicularis). Behavioral Ecology and Sociobiology, 68(4), 583–595.
Setchell, J. M., & Wickings, E. J. (2006). Mate Choice in Male Mandrills (Mandrillus sphinx). Ethology, 112(1), 91–99.
Walker, K. K., Rudicell, R. S., Li, Y., Hahn,. (2017). Chimpanzees breed with genetically dissimilar mates. Royal Society Open Science, 4(1), 160422.
Widdig, A., Bercovitch, F. B., Streich, W. J. (2004). A longitudinal analysis of reproductive skew in male rhesus macaques. Proceedings of the Royal Society of London. Series B: Biological Sciences, 271(1541), 819–826.