When Science Goes Awry

Two-thirds of the way through my field study of chacma baboons in the Okavango Delta, my dissertation research was collapsing. To rescue the project, we began darting and immobilizing the study animals to collect blood samples and other physiological data. During one anesthetization, a mother lay unconscious while her infant was grabbed and killed by a recently arrived adult male. Two weeks later, I witnessed a related event that fundamentally changed how I understood chacma baboons — and sent my research in an entirely new direction.

A Failing Dissertation Project

In 1977, I began my dissertation research in a remote area deep in the Okavango Delta of Botswana. The three-year study of baboon diet and nutrition was directed by Professor William J. “Bill” Hamilton III of U.C. Davis and funded by the NIH.

I was joined in the field by fellow students Steve Smith and Barbara Kus. Together, we established a new camp and eventually gained the confidence of two troops of chacma baboons totaling roughly 140 animals. For two years I followed the baboons on foot through this pristine habitat, recording everything they ate.

The work was painstaking and, at times, monotonous. Often I found myself more interested in sleeping beneath baboon sleeping sites at night, hoping to document leopard attacks. The nutrition study itself was producing less insight than we had hoped, and by 1979 my dissertation project was in trouble.

To strengthen the study, Bill brought in Derek Melton, a postdoctoral researcher, and his wife Carol to collect blood samples and physiological measurements that could be correlated with dominance hierarchies and social behavior. Their arrival injected new energy into camp, both scientifically and socially.

Derek and Carol somehow transformed our isolated bush camp into a functioning field laboratory. Bill also brought in Dr. Murray Fowler, a renowned veterinarian from U.C. Davis, who arrived with everything needed to dart and anesthetize large numbers of baboons. During a week-long crash course, he trained us to use a simple yet ingenious blow-dart system: a three-foot aluminum tube and syringe darts loaded with carefully measured doses of Ketamine.

Betraying the Baboons’ Trust

The darting plan was, in a sense, insidious.

For two years Steve and I had worked patiently to gain the baboons’ trust. The animals had gradually learned that humans on foot posed no danger. Now we were preparing to exploit that trust. The baboons had no idea what was coming.

The first darting appeared to go perfectly. Derek casually positioned himself behind an adult male sitting on the ground with his back turned. He inserted the dart into the blowpipe, raised it to his lips, and fired.

The dart struck the baboon in the lower back and remained lodged in the muscle. The startled animal ran about twenty yards, stopped, sat quietly for a moment, and then slowly collapsed as the drug took effect (photo).

Blood samples were collected, dental impressions made, and body measurements recorded. An hour later the baboon was walking again, though groggy, and soon rejoined his troop wearing brightly colored plastic ear tags.

At first the process seemed manageable, but complications soon emerged. One darted baboon climbed high into a tree before the Ketamine fully took effect and fell heavily to the ground like a limp mannequin. Fortunately, the deep sand broke the fall.

After that, whenever a darted animal climbed a tree, four of us sometimes stood beneath it holding a blanket stretched tight like a fire net, hoping to catch it before it hit the ground. It was quite unnerving, but during the first several dartings the baboons suffered no apparent injuries.

We even successfully darted a mother carrying a small infant (photo), which calmly clung to her throughout the procedure.

Then disaster struck.

The Death of Muni’s Infant

On September 1, 1979, we darted a female named Muni (CMU), who carried a four-day-old infant. Before the drug took effect, she disappeared into dense vegetation and we lost sight of her.

Nine minutes later we heard loud calls and the sounds of two males fighting.

We found Muni unconscious in tall grass. Her infant was gone.

Moments later we spotted the adult male Bamm-Bamm (CBB) sitting in a nearby tree, biting into the infant’s lifeless body (photo).

The possibility of infanticide in baboons had barely been on our radar. Such behavior was best known in monkeys like langurs that lived in single-male groups. Reports from baboons existed, but they were rare and largely anecdotal.

The evolutionary explanation was disturbing but straightforward. When a new male entered a troop and rose to dominance, he could increase his own reproductive success by killing unweaned infants fathered by other males. The death of the infant caused the mother to return to fertility sooner, allowing the new male an opportunity to sire offspring of his own.

The idea ran counter to older notions that animals behaved “for the good of the species.” Yet by the late 1970s, evidence supporting infanticide as a male reproductive strategy was steadily accumulating across many mammals.

After the trajedy of Muni’s infant, Bill immediately halted all darting of mothers carrying infants. At first we assumed the incident had been an isolated tragedy triggered by human interference.

But only nine days later, Bill and Steve witnessed another attack near camp at dusk. An adult male bit a nine-month-old infant, which died overnight from a puncture wound below the ear.

Something far more important was happening within chacma baboon society than we had understood.

Diminishing Returns

By then our darting operations were also becoming more difficult. The baboons had grown wary of Derek and no longer allowed him to approach closely. Steve and I eventually took over much of the darting ourselves.

Over the next four months, each of us darted roughly twenty-five baboons.

For two years these animals had allowed us to observe their lives at close range. We knew them individually. We recognized personalities, family relationships, and dominance hierarchies. Now we were betraying the trust we had carefully built.

It was painful. Some nights I lay awake knowing that the next day would be my turn with the blowpipe.

In the 1970s, darting wild animals was widely accepted in field biology and even celebrated in wildlife documentaries. Today, new technologies have largely replaced such methods. GPS tracking, noninvasive hormone studies, genetic analyses from fecal samples, and remote monitoring techniques have transformed the field. Darting wild baboons to gather physiological data would now be much harder to justify.

The Observation on White Island

Thirteen days after the death of Muni’s infant, I was following our other study troop on White Island. It was a quiet afternoon. The baboons spread peacefully through open grassland dotted with acacia trees.

At one point I focused on a female named Farah (WFR) and her seven-week-old daughter, Fanni (WFI). Nearby sat Captain Kirk (WCK), the troop’s second-ranking male and the only male I had seen consorting with Farah during the period when Fanni had been conceived.¹

Although irrelevant to my nutrition study, I strongly suspected that Captain was Fanni’s father.

As the three rested together, another male approached through the grass. It was Norbert (WNR), the new alpha male who had immigrated into the troop roughly two and a half months earlier. Since baboon gestation lasts about six months, Norbert could not have fathered Fanni.

As Norbert drew closer, young Fanni climbed onto Captain’s lap. Captain lifted the infant and stood facing Norbert in a stiff, defensive posture. Fanni clung upside-down to Captain’s belly while both males stared at one another.

Farah remained calm.

At the time, this type of interaction was known as “agonistic buffering.” In several baboon and macaque species, lower-ranking males were known to hold infants during tense encounters with more dominant opponents. The standard explanation was that the infant acted as a kind of social shield, reducing the chance of aggression toward the male holding the infant.

I had occasionally seen similar interactions in our baboons, but I had paid them little attention.

Then, suddenly, the pieces fit together.

Captain was not protecting himself. He was protecting Fanni.

A New Direction

Sitting there on White Island, with the recent infanticides fresh in my mind, I realized that I had spent two years watching baboons without fully understanding what I was seeing.

The patterns suddenly became obvious.

Mothers often stayed close to likely fathers and appeared calm and relaxed in their presence, as did their infants. In striking contrast, mothers — but not other adult females — showed clear anxiety around newly arrived males, especially by raising their tails, avoiding them, or sometimes screaming as they approached.

During interactions between males involving an infant, the male holding the infant had almost always been present — and often had been observed mating with the mother — when the infant was conceived. The opposing male, by contrast, was typically a recent immigrant who could not possibly have been the father.

And, as we had just discovered, such immigrant males could pose a mortal threat to infants.

I sat watching Captain, Farah, and Fanni for more than an hour while my mind raced through the implications. Norbert wandered away and the tension gradually eased. Fanni resumed stumbling and playing near Captain, often within inches of him.

During the long hike and drive back to camp, new research questions flooded my mind. Before I even reached camp, I knew I wanted to abandon my dissertation on baboon diets and focus instead on relationships between adult males, mothers, and infants.

When I told Bill what I had seen, he was skeptical at first. The next morning we drove out together to White Island and followed Norbert for a few hours. Everywhere he went, mothers with young infants reacted nervously, especially by raising their tails when he neared.

By the end of the day, Bill had seen enough and he agreed to let me change my dissertation topic.

A Discovery Hidden in Plain Sight

For the next nine months I focused almost entirely on interactions between mothers, infants, and adult males. I documented which males mothers associated with, how females reacted to immigrant males, and how infant handling varied depending on probable paternity.

Unlike the feeding study, this was exhilarating work.

The darting project had begun as an attempt to rescue a struggling nutrition study. It inadvertently exposed a hidden and deeply unsettling feature of chacma baboon society. By temporarily disabling a mother’s ability to protect her infant, we unintentionally revealed a danger that normally remained concealed by the checks and balances of baboon life.

It was a discovery born from a mistake — one that permanently changed both my research and my understanding of these animals.

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1. Studies of baboons have shown that females are most likely to conceive during a brief three-day period immediately before their perineal swelling begins to detumesce. This timing suggests that the peak swelling phase serves as a reliable visual signal of ovulation and maximum fertility.
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2. The home ranges of our two study troops, White Island (W) and Camp (C), barely overlapped. They rarely encountered each other, and no males transferred between the troops during the study period. ↩︎