For reasons I explain later, this seniority system is common in large groups of macaques. In these groups some alpha males are never challenged and maintain their status for years. Some males on Cayo Santiago have held alpha rank past the age of twenty years, even as they start to look decrepit. This wouldn’t happen in the wild, where male macaques are lucky if they live past ten or twelve years. In the forests of Asia, where the macaques live, alpha males are never left to die of old age but instead are challenged in a duel—as in the Wild West of Sergio Leone and Clint Eastwood’s “spaghetti western” movies—by a lone stranger who appears on his white horse out of nowhere and takes over the town by shooting the sheriff and his deputies, wasting no time in talk or politics.
THE CHALLENGER IMMIGRANT
In 1975, primate researcher Bruce Wheatley studied the behavior of a group of long-tail macaques in a region of Borneo, Indonesia, called East Kalimantan for several months. The group Wheatley had been following included three adult males, two subadult males, and ten adult females with offspring of various ages. On March 10, he observed the following events. Three strange adult males and one subadult male entered the tree where Wheatley’s macaque group was sleeping and threatened its members. One of these four intruders, named Rambo (Wheatley actually named this male GL, but Rambo sounds better), performed many branch-shaking displays in the parts of the tree where everyone could see him. The following morning the four strange males followed the troop as it foraged in the forest, and Rambo continued to act cocky and defiant, walking around with his shoulders straight and his tail up. That afternoon, when the group stopped to rest in a tree, Rambo attacked and chased the group’s alpha male up and down the tree, until the alpha male eventually abandoned both the tree and the group. In merely two days, and without any bloodshed (or any help), Rambo became the group’s new alpha male—the deposed king was never seen again.
Rambo was a large male, probably around seven or eight years old, in his physical prime. He had self-confidence and good fighting skills, and he was attractive to females, which explained why they readily accepted him as the new alpha male. He remained the alpha male of that group for two years, during which he mated copiously and sired many offspring. Two years later, however, a new lone stranger rode his horse into town. He challenged Rambo, as Rambo himself had done. When Rambo was seriously wounded in the fight, he was kicked out of the group. After his wounds healed, Rambo approached another group and once again challenged the alpha male. This was a group, however, of over eighty macaques, including more than ten adult males. The resident males supported the alpha male against Rambo’s challenge, and Rambo got his butt kicked once again. After he wandered alone in the forest for a couple of days, one of his wounds became infected; the following day, Rambo died quietly behind a bush.
Challenger immigrants—sometimes called bluff immigrants—such as Rambo are males in their physical prime. They are strong and impulsive and have no patience for waiting in line. Their challenges may be successful when they join a small group, but they almost invariably fail—for reasons I will explain—when a large group is involved. In large groups, the most common way for a male immigrant to rise in rank is through succession. But not everyone is as lacking in ambition as Billy. For all the impatient ones, there is another option—illustrated by the following story of Max the challenger resident.
THE CHALLENGER RESIDENT
Dutch primatologists Maria van Noordwijk and Carel van Schaik studied long-tail macaques in the forests of Sumatra, Indonesia, in the early 1980s. They followed several groups of these monkeys, every day, for a few years. In one of these groups, they observed an adult male they named Max successfully challenge and dethrone the alpha male.
Unlike Rambo, Max did not challenge the alpha male the day after he tried to join his group. Max had joined the group a couple of years earlier, when he was still a subadult and had not yet reached full adult size. He immigrated into the group unobtrusively, accepting a low-ranking position in the hierarchy. He had been accepted because he behaved submissively to the resident males and tried to make friends with the females, some of whom, as they got to know him better, liked him even better than the group’s high-ranking males. Max kept a low profile for a couple of years, concentrating on eating good meals, sleeping well at night, and occasionally having sex with a couple of females who seemed to like him. He was careful not to do it in the presence of the alpha male, so he didn’t get into too much trouble. During these two years, presumably, he carefully observed the behavior of the alpha male and the other adult males and females, creating a mental record of who was friends or enemies with whom.
One morning Max felt confident enough to launch his attack on the alpha male. The alpha male was stunned by Max’s impudence, presumably became very angry, and fought back. He was helped in the process by the beta male, and their counterattack was initially successful. Max, however, did not give up his ambitions of group domination. He continued to challenge the alpha male, day after day, for two months, until finally the alpha male gave in and left the group with his tail between his legs.
As with the challenger immigrants, successful challenger residents are fully grown adults in their physical prime. They are generally more successful in takeovers than challenger immigrants, perhaps because of the amount of social knowledge they have been able to accrue. Having spent a year or more in the group, the challenger residents know the others and are known by them as well. Challenger residents do not attempt to challenge alpha males who have recently attained their status because they know these alpha males are strong. Knowing your opponent’s strength is crucial if you want to take the risk of challenging him for the top spot. Challenger residents also probably know whose attacks can be ignored, who is likely to form strong defensive coalitions, and who should be defeated first.
Alpha males never give up their status without a serious fight, and challenges sometimes take place over the course of several weeks or even months. But because of their knowledge and strategizing, challenger residents are often successful. They launch their challenges when their chances of success are highest—for example, after the incumbent has been dominant for more than a year and has lowered his guard, making some enemies within his own group.
Models of Ladder-Climbing Strategies
The stories of Billy, Rambo, and Max show that male macaques, like new Microsoft employees or young researchers at the beginning of their academic career, have at least three different strategies to attain high rank after they immigrate into a new group. But why do these strategies exist in the first place, and how do monkeys make decisions about which strategy to use? As usual, the answer has to do with the costs and benefits. A monkey chooses a particular strategy when its benefits are greater than its costs and when the benefit-to-cost ratio of this strategy is higher than that of the others.
For the macaques, the main cost of challenging an alpha male is the risk of injury or death. To understand the benefits of being the alpha male or of being high-ranking in general, we need to understand the nature of male-male competition in the macaque world. Male macaques compete with one another to mate with females and produce offspring the way people compete with one another for money. Primatologists distinguish between two kinds of competition: contest and scramble. Imagine a group of one hundred macaques with ten adult males and fifty fertile females. One way in which the ten males can compete to impregnate the fifty females is by fighting with each other and establishing a dominance hierarchy that regulates access to the females, so that the top-ranking male mates a lot and the others mate less; the lower their rank, the less they mate. This is contest competition. Alternatively, each male could try to mate with and impregnate as many females as possible without directly interfering with the other males and fighting with them. This is scramble competition.
The extent to which male-male competition is by contest or scramble varies across different species of primates, and even across different groups of the same species. At one e
nd of the continuum is the “super-contest.” This is essentially a winner-take-all market: the alpha male mates with all the females, while the other males get little or no action. A good human example of a winner-take-all market is the Hollywood film industry, in which a select few actors and actresses receive multimillion-dollar paychecks for every film they make, while thousands of other actors are perpetually unemployed or get paid minimally for their performances. (This is also the case in the book publishing business, in which a handful of best sellers make millions of dollars, while millions of best seller–wannabe books sell only a few hundred copies or don’t get published at all.) In a winner-take-all market, the odds of making it to the top are extremely low, but the benefits of being at the top are so high that many people—and many macaques—are willing to try to play the lottery.2 All actors and actresses dream of being as successful as George Clooney and Angelina Jolie, and all male macaques dream of being alpha males.
At the other end of the competition continuum is the “super-scramble.” This is a situation in which dominance rank has no effect on the ability to mate because males of all ranks have equal probabilities of impregnating females. In a group in which male-male competition is by super-scramble, dominance hierarchies don’t exist because there is no clear benefit in having them (unless rank confers other advantages, like eating better food and living a longer, healthier life). An example of scramble competition in humans would be a berry-picking contest in which a group of people walk through a forest carrying baskets and each person tries to pick as many berries as possible without interfering with the other contestants.
Carel van Schaik and his colleagues developed a mathematical model that shows that, as male-male competition shifts from super-contest to super-scramble, corresponding changes occur in male strategies of rank acquisition.3 In the model, they use a variable—represented by the Greek letter beta—to indicate the extent to which competition in a species or a group is a contest or a scramble. In the model, beta is a number between 1 and 0. When beta equals 1, we have a super-contest, and when beta is 0 we have a super-scramble. The value of beta depends mainly on how many females live in a group and whether mating takes place every month of the year or during a restricted breeding season. In the real world, beta can be estimated by examining the DNA of all the adult males and all the infants born within a group: if all the infants have the same DNA as the alpha male, it means that beta is 1, whereas if the DNA analysis shows that the infants have been fathered by many males within the group, beta is low.
When beta is close to 1—as in a winner-take-all market—there is strong pressure to use high-risk tactics of rank acquisition, because the potential benefits of alpha status are high. When beta is close to 0 and the monkeys are picking berries for their baskets, low-risk tactics like the queuing system are popular. It is important to clarify that in a winner-take-all market it is worth challenging only the alpha male, who has all the power, and no one else. This is why, when challenger immigrants join a new group, they invariably challenge the alpha male. They would not try to enter the male dominance hierarchy in the middle by challenging some of the low-ranking males. Challenging other males and risking an injury is simply not worth it because the benefits of winning are so low. Being in a winner-take-all market, however, doesn’t necessarily mean that a male will challenge any alpha male he encounters any place, any time. Smart males decide to launch a challenge only when the probability of success is high.
A macaque male who wants to immigrate into a group with high contest competition must decide whether he should challenge the alpha male immediately or wait a while. Two things seem to affect this decision: the immigrating male’s own resource holding potential (see Chapter 2) and the RHP of the alpha male. To succeed in attaining top rank through a challenge, a male must be in prime physical condition. The immigrant male can assess his own RHP from his age and size—whether he’s big and strong or small and skinny—and also whether he feels good about himself or is low on self-confidence. Interestingly, male macaques who were born to high-ranking females in their group of origin seem to be more successful at obtaining alpha status as challenger immigrants than males who were the sons of low-ranking females in their group of origin. Although their mothers are not there to help them in their challenge, the sons of high-ranking females may be in better physical condition (because they ate more and better food growing up) and have more self-confidence than the others.
The real problem for an immigrant male considering an immediate challenge is to determine how much RHP the alpha male has—that is, whether he will be a tough opponent or a weak one. Primatologist Joe Manson has argued that an immigrant male can use the number of males in the group as an estimate of the RHP of its alpha male.4 Manson developed a mathematical model that shows that the more males there are in a group, the more powerful the alpha male must be. Furthermore, the alpha male’s RHP increases fairly slowly with an increasing number of males, but does so quickly for small groups that contain, say, between three and ten resident males. So an immigrant male macaque who understands math and is familiar with Manson’s model should know that if there are only three males in a group, the alpha male is probably not that strong and an immediate challenge may be worthwhile. In a group of five or six males, the alpha male is probably stronger and has more support from the other males, so an immediate challenge may be too risky. The immigrant male may be better off waiting a few months before launching a challenge. By waiting, the immigrant male also has the opportunity to gather cues as to whether he might receive political support from other group members if he attempts a takeover (or whether they will at least refrain from joining coalitions against him).
Again, the sons of high-ranking females seem to have more success as challenger residents than the sons of low-ranking females, perhaps because they have expectations, based on their experience in their natal group, that they will receive effective support if they are involved in a fight. In large groups with more than fifteen or twenty males, the RHP of the alpha male ceases to be an issue. With so many males in the group, it is virtually impossible for an alpha male, regardless of how powerful he is, to monopolize the mating market. This means that there is scramble competition for mating—beta is low—and being the alpha male is not particularly beneficial; therefore, an immediate challenge for alpha status is simply not worth the cost. In this situation, males are expected not to take risks and to immigrate unobtrusively.
Does this mean that in large groups of macaques males have no option but to wait in line—sometimes for years—for their turn to rise to alpha rank? Not necessarily. Although males must choose between different strategies for rank acquisition at the time of immigration, there may be opportunities for advancement at any point during their residence in the new group—opportunities to cut the line and reach alpha status quickly, even overnight. While immigrating males, regardless of the chosen strategy, typically act alone, males who have been resident in a group for a long time can obtain the support of other group members, typically other males. In male macaques as in humans, a successful politician is able to form coalitions or political alliances with others. And these coalitions aren’t formed only in monkey species in which males transfer between groups, such as macaques and baboons, but also in species, such as chimpanzees, in which adult males remain in their natal groups all of their lives. Chimpanzee males form political alliances with other males—sometimes with brothers, other times with unrelated males—to gain power and climb the dominance ladder in their group, to help others gain power, or to maintain the power they already have. As in human societies, struggles for power among chimpanzees rarely involve individuals acting alone; ambitious and successful individuals always operate with a strong base of political support.
Primate Politics
Before I go on about male-male coalitions in primates, it may be helpful to introduce some definitions. A coalition involves two or more males fighting together against a target, which in most cases is a
single individual but occasionally is another coalition of two or more individuals. If a male is under attack, another male comes to his defense, and together they fight against the aggressor, these two males have formed a defensive coalition. If, instead, two or more males join forces to initiate an attack against a male who didn’t previously attack either one of them, the coalition is called offensive.
Let’s forget about defensive coalitions for the moment and focus on the offensive ones. Offensive coalitions can be formed for different reasons. As we saw in Chapter 2, when a high-ranking male baboon spends a lot of time near a female in estrus, males may pair up to form an offensive coalition against him, so that one of them might get a chance to mate with the female. In other situations, males form offensive coalitions because they want to maintain or change their dominance relationship with the target. In these cases, the fight is about power. There are three basic types of offensive coalitions: those in which the two coalitionary males are higher-ranking than the target (conservative coalitions); those in which one coalitionary male is higher-ranking and the other is lower-ranking than the target (bridging coalitions); and those in which the two coalitionary males are both lower-ranking than the target (revolutionary coalitions), which, unsurprisingly, turn out to be the most interesting.
Let me illustrate how revolutionary coalitions work. In June 2009, my research collaborator James Higham was studying a large group of rhesus macaques on the island of Cayo Santiago when he observed a series of revolutionary coalitions that resulted in drastic changes in the male dominance hierarchy within the group.5 Over a period of two and a half months, a bunch of middle-ranking males repeatedly ganged up against four higher-ranking males (this was a large group comprising over twenty adult males) and eventually managed to change the dominance hierarchy and outrank the targets. Before the coalitionary attacks began, the four targets were ranked one, two, seven, and ten, so they included the alpha and beta males. The main “revolutionaries” were five males who ranked just below the tenth-ranked male, although at times they were supported by a few lower-ranking males and even some females.
Games Primates Play: An Undercover Investigation of the Evolution and Economics of Human Relationships Page 12
