There are a million stories in the naked jungle. Some of the strangest ones take place on the savanna street corners where baboons hang out. People need look no further for weird, even kinky, tales of life among the feral, fierce, and furry.
Baboons’ odd practices offer more than vicarious thrills for nature buffs, though. In the wild, these regal-looking, powerfully built monkeys behave in ways that raise intriguing questions about what goes on in their minds.
Consider this peculiar sight: An adult male baboon strides stiff-legged up to another male while flashing a “let’s-make-nice” facial expression, turns around, and permits the other fellow to briefly touch his genitals. In the macho world of male baboons, guys otherwise avoid each other between the skirmishes that determine the privileges of social authority, such as prime access to mates. Why would the greeting monkey place his reproductive future literally in the palm of an opponent’s hand?
Adult female baboons exhibit a perplexing habit of their own. Understandably, they often emit a full-throated barking sound if separated from either their troop or their infants. However, if a youngster that has wandered off starts screeching in distress, its mother stays mum. Sure, she looks toward her child’s call and may rush off in that direction. Yet despite the threat of predators and infanticide-minded male baboons, the mom refuses to employ the search tactic of calling back and forth with the disoriented tyke. Why not reach out and bark to someone?
Separate research teams are trying to figure out what these puzzling behaviors signify about baboons’ mental states. Preliminary explanations vary widely in their implications for how the animals think.
“Male baboons engage in common, highly variable, and complex ritual greetings,” asserts anthropologist Barbara B. Smuts of the University of Michigan in Ann Arbor. “We know little about these rituals, but they’re a rich source of information about how baboons communicate and think.”
Smuts suspects that trust builds from successful completion of greetings, which are most common among older males. Such salutations may even act as a nonverbal promise to help each other in driving young, dominant males away from sexually receptive females. After dispatching a young suitor, members of these “over-the-hill” gangs alternate in approaching the female.
In contrast, female baboons’ silence in the face of their lost infants’ cries suggests that these adult monkeys fail to grasp that other individuals have thoughts and feelings, contends psychologist Drew Rendall of the University of Lethbridge in Alberta.
“Complicated-looking behavior in baboons, including male greetings, may not require sophisticated social and cognitive capacities,” he says.
Monkeys and apes—even chimpanzees trained to use simple languages—remain mute on the subject of whether they ponder either their own thoughts or those of others. Until several years ago, many scientists were receptive to the idea that a variety of nonhuman primates can understand, to some extent, that they and others have motives and intentions.
A new breed of laboratory experiments, however, has challenged that assumption (SN: 1/20/96, p. 42). For example, when confronted with two people pointing to different cups, chimpanzees choose randomly and don’t seem to realize that they can snag a snack by heeding the person whom they previously saw hiding food under one of the cups.
Although groups of chimps appear to pass on their own traditions of tool use and social communication (SN: 6/19/99, p. 388), monkeys may not do so. Field observations have yielded no conclusive evidence that monkeys impute thoughts or emotions to others, intentionally imitate what others do, or teach each other even simple food-gathering skills.
Still, it’s too early to draw firm conclusions about the mental workings of nonhuman primates, Smuts says. Greetings between pairs of male baboons provide glimpses of what look to Smuts like learned performances. Each greeting incorporates a set of conventional behaviors while still allowing for on-the-spot negotiations about who does what to whom and how far to go.
Smuts and anthropologist John M. Watanabe of Dartmouth College in Hanover, N.H., have documented, over a 4-month period, 637 greetings among 12 adult males in a troop of 150 baboons in Kenya. Smuts has also videotaped 400 such greetings in another baboon troop of comparable size.
Watanabe summarized his and Smuts’ findings in February at the Annual Meeting of the American Association for the Advancement of Science in Washington, D.C. A typical greeting begins with one male walking upright rapidly toward another with a straight-legged, rolling stride. The approaching male looks directly at his intended partner while making friendly gestures, such as smacking his lips, flattening his ears back, and narrowing his eyes.
Often, the second male maintains eye contact and smacks his lips in return. In that case, the animals get up close and personal. They often begin with a quick hug or nuzzle. One then presents his hindquarters; the other grasps them, mounts the reversed partner, and touches his scrotum or gently pulls his penis. Sometimes, participants exchange active and passive roles during a single greeting.
After a completed greeting, which usually lasts no more than a few seconds, both males walk away using the stiff-legged gait characteristic of the approach.
Greetings tend to proceed in ways that reflect the animals’ willingness to cooperate with one another, Watanabe says. Young adult males—each in his physical prime and able to obtain mates on his own—seldom team up, and pairs of these toughs usually fail to complete greetings.
They often circle each other, jockey to position themselves as the active partner, and end up either walking away or getting into a minor scuffle. Young adult males sometimes approach older males and almost always take the active role in the ensuing encounter. The older males, being less dominant, usually accept this arrangement but exhibit signs of wariness and worry. Younger males may seek to buddy up to senior comrades who have influential female friends within the troop, the researchers suggest.
Such a strategy seems plausible. Young adult males move from their native troops into new troops, whereas females stay put, living among close relatives. Older males typically have lived in the same troop long enough to have forged opposite-sex bonds. In her earlier work, Smuts charted strategic friendships that develop between baboons that enable the male to benefit, for example, from the female’s greater access to food resources, and the female to gain protection by the male.
Greetings among pairs of older males stand out dramatically in the emotionally charged atmosphere of male baboon society. Older male partners stayed relatively relaxed during the large majority of their mutual greetings, Smuts and Watanabe say.
Two older males in particular, Alex and Boz, greeted each other much more often than any other pair did. Familiar to one another after having lived in the same troop for 7 years, they took turns at adopting active and passive roles in successive greetings. Neither made any attempts to dominate the other. Alex and Boz were the only pair of males observed defending one another in fights with other males.
Older males mated at least as often as, and in some cases more often than, socially dominant younger males, Smuts and Watanabe report. Two or more older males jointly harass a younger individual about to mate with a female and drive him off. The abandoned female usually proves willing to mate with the older male who steps in, while his cronies keep the younger male at bay.
The older males who had the most such liaisons had participated in the most completed greetings with one another, the investigators say.
Male baboon greetings resemble the human ritual performances that the late cultural anthropologist Roy Rappaport considered essential for establishing social trust and symbolic communication, Watanabe contends.
As Rappaport saw it, people perform ritual acts that include a limited set of nonverbal gestures imbued with a shared meaning and then used in specific situations to signal an intention to cooperate.
Male baboons do much the same thing, Smuts and Watanabe theorize. The creatures appear to borrow gestures from other situations to compose greetings that have a new meaning. The lip smacking, nuzzling, and embracing come from the intimacy of mother-infant relations, and the presenting of hindquarters, mounting, and genital contact derive from mating behavior.
Each partner who follows through on a greeting conveys cooperative intent while assuming that the other shares his aims, Smuts proposes. Finished greetings may even serve as promises of future aid in hijacking mates from the young bucks, in her view.
Comparable behavior exists in human societies, the researchers note. The words testicle, testify, and testimon share the common Latin root testis, meaning witness. This may reflect the Roman practice of a man swearing to tell the truth by touching his forefinger to his testicles to bring sterility upon himself if he lies, the researchers propose.
Moreover, in certain populations of Australian Aborigines, men visiting from neighboring communities pledge their good intentions in a ceremony during which each presents his penis to a lineup of his male hosts, each of whom briefly grasps the genitalia of those men whom he trusts.
Much simpler types of ritual behavior have long been noted in a variety of animals, such as the cringing torso and downcast eyes favored by dogs trying to avert fights. If Smuts and Watanabe have found that baboons go further by inventing and passing on behavioral conventions for forming alliances, “that would be very interesting,” remarks zoologist Frans B.M. de Waal of Emory University in Atlanta. “It’s possible.”
Richard W. Byrne, a primatologist at the University of St. Andrews in Fife, Scotland, disagrees. Male baboon greetings represent “normal communicative behaviors, not ritual,” he asserts. Comparable coalition-building occurs when male and female baboons choose grooming partners, without necessarily considering one another’s motives or assuming that the act implies some kind of a promise, according to Byrne.
The unanswered cries of lost youngsters may underscore baboons’ inability to recognize that other animals have knowledge, thoughts, and feelings, says Rendall.
Over a 14-month span, Rendall—working with Dorothy L. Cheney and Robert M. Seyfarth, both of the University of Pennsylvania in Philadelphia—recorded calls produced by 22 females in a baboon troop in Botswana.
Females regularly belted out barks when they became separated from the group, the researchers say. In contrast, the same baboons usually made no response to calls of others, even their own infant wailing pitifully from some unknown location.
In one experiment, mothers heard recordings of distress calls from either their own infants or unrelated infants of the same age and sex as their own. Mothers only reacted to the cries of their own infants and sometimes hurried in the direction of the calls, the researchers report in the March Journal of Comparative Psychology. But the baboon moms remained silent.
“Somehow, they don’t make the connection that ‘if I call, it will affect what my kid knows,'” Rendall contends. An internal sense of fear associated with separation from the group, rather than an appreciation of others’ mental perspectives, probably causes baboons to bark in distress, he theorizes.
Alternatively, baboon mothers may not return their infants’ calls because they don’t want to tip off predators and adult baboon males to the presence of an isolated child. Young adult males, relatively unencumbered by opposite-sex friendships, will kill infants if given the chance so that their mothers will become sexually receptive more quickly.
Rendall doubts this explanation, however. Adult males and females in several baboon species that have been studied also let each other’s calls go unanswered, he says.
Even though Byrne doesn’t think that baboons consider what another animal might be thinking, he suspects that female baboons know that responses are sometimes appropriate to another’s call. Female baboons indeed often bark in response to calls that they recognize as coming from a close adult relative, Byrne says.
“It seems nuts that mothers wouldn’t immediately respond vocally to the distress calls of their infants,” he maintains. “I don’t have a good explanation for Rendall’s finding.” In many species of birds and mammals, particularly those that nest or give birth in colonies, mothers and their infants exchange individually distinctive calls or sounds to find one another when they get separated, Smuts notes.
For instance, wild bottlenose dolphin mothers and their wandering infants whistle to one another, most often when they get close to each other just before reuniting. Dolphin infants do most of the whistling, probably to convey information about their identity, location, and desire to reunite, Smuts and two colleagues found in a 1993 investigation.
Communication between baboon mothers and infants, who likewise live in tightly knit groups, remains poorly understood, Smuts asserts. For that matter, she says she has only scratched the surface of male baboon greetings.
Both she and Rendall plan to continue their respective lines of research on baboon cries and greetings. As the plot thickens, stories in the naked jungle will undoubtedly add new chapters.