Tag: Animal Culture & Knowledge

  • The Ngogo Chimpanzee War: The First Documented Civil War in a Non-Human Species

    On the last full day of his life, a chimpanzee named Basie woke at dawn in a tree nest he’d built from branches and leaves, surrounded by other chimps dozing in their own nests, as he’d done nearly every day for 36 years in the Kibale National Park rainforest in Uganda. He spent an ordinary day swinging between trees and eating figs. As daylight faded, a patrol of about 13 adult chimpanzees from the opposing faction arrived. Three surrounded him. He jumped from a tree. Ten piled on him on the ground, biting him. Basie’s killers were chimpanzees he had grown up with — individuals he had groomed, traveled with, and defended territory alongside for decades. His death in 2019 was the second casualty in what researchers now call the Ngogo chimpanzee civil war, an eight-year conflict that has killed at least 28 chimpanzees, including 19 infants, and that a study published in Science on April 9, 2026, has documented in detail that primatologists say is unprecedented.

    What happened

    The Ngogo chimpanzee community was the largest known group of wild chimpanzees on earth — approximately 200 individuals living in relative cohesion in Kibale National Park for at least 20 years under continuous scientific observation since 1995. Chimpanzee communities typically number around 50. Ngogo was four times that. The group operated through a fission-fusion social structure — small parties formed and dissolved throughout the day as individuals moved around the territory foraging and socializing, but everyone belonged to the same community, shared the same territory, and collectively defended it against neighboring groups. Within the community, social relationships clustered around two primary neighborhoods that researchers named the Central and Western groups, but the boundary was porous. Chimps changed which cluster they associated with. Males groomed partners from both groups. Females mated across the divide. Key individuals — socially connected males who maintained relationships in both clusters — served as bridges holding the community together.

    Then those bridges collapsed. Several of the bridging males died from disease. A new alpha male rose to power, shifting the community’s political center of gravity. A respiratory disease outbreak further destabilized social networks. By approximately 2015, chimps in the Western and Central clusters began avoiding each other. The avoidance hardened into separation. By 2018, the division was permanent — two distinct communities with separate territories, separate social hierarchies, and no remaining social bonds between them.

    What followed was not a border skirmish between strangers. It was coordinated lethal violence between former companions. The Western faction — numerically smaller, starting at about 76 individuals — launched targeted raids into Central territory. Groups of adult males would patrol into enemy territory, locate isolated individuals, and attack with overwhelming numbers. The violence was graphic: sustained group assaults, biting, mutilation. From 2021, the Western raiders began targeting and killing infants — a pattern that primatologists associate with territorial expansion, as infanticide eliminates the offspring of rivals and can make females sexually receptive sooner.

    The Western faction’s campaign has been described as a “one-sided rout.” Their numbers grew from 76 to 108 over the course of the conflict. The Central faction suffered a stepwise decline. John Mitani, a professor emeritus at the University of Michigan who had been studying the Ngogo chimps for two decades when the violence started, told NBC News he is concerned the Central group is “doomed.” The war is ongoing. The 2026 Science paper covers data through 2024, but lead author Aaron Sandel of the University of Texas at Austin confirmed that further attacks have occurred in 2025 and 2026.

    Why it matters

    This is only the second documented case of a chimpanzee community splitting and going to war with itself. The first was the Gombe Chimpanzee War of the 1970s, observed by Jane Goodall in Tanzania, where a community called the Kasakela fissioned and the splinter group (the Kahama) was systematically hunted and destroyed over four years. The Gombe war was groundbreaking but limited by the observational methods available in the 1970s. The Ngogo study benefits from 30 years of continuous demographic data, 24 years of systematic behavioral observations, a decade of GPS tracking, and structured social network analysis — a dataset that Gombe never had. Genetic evidence suggests that permanent community fissions in chimpanzees are extraordinarily rare, occurring roughly once every 500 years. Researchers have now documented two in 50 years of field primatology, which either means the estimate is wrong or scientists have been spectacularly unlucky — or lucky, depending on your perspective.

    The social network data is what makes the Ngogo study new. The 2026 Science paper mapped the social ties between individuals across the entire community for years before, during, and after the split. What they found is that the division didn’t happen along genetic lines, or resource boundaries, or any clear ecological gradient. It happened along social network lines. When the bridging individuals who maintained connections between the two clusters died or were removed, the network fragmented — and fragmentation preceded violence by approximately three years. The chimps didn’t fight and then separate. They separated and then fought. Avoidance came first. Identity formation second. Lethal violence third.

    Aaron Sandel told BBC Science Focus that the study provides “a window into the chimpanzee mind that’s really rare” — the transition from friend to enemy, visible in behavioral data over a decade. The implication for understanding human conflict is the part that’s getting the most attention. In humans, collective violence is typically explained by cultural differences — ethnicity, religion, language, ideology — that bind groups together and generate hostility toward outsiders. But the Ngogo chimps had no cultural markers distinguishing the two factions. They spoke the same calls, ate the same food, lived in the same forest, and had mated with each other for years. The split wasn’t driven by what made them different. It was driven by the decay of what had kept them connected.

    Sandel’s conclusion is pointed: if chimpanzee civil wars emerge from the breakdown of interpersonal relationships rather than from intergroup differences, then human peace interventions that focus on cultural diplomacy — learning about the other side’s traditions, bridging ideological divides — may be missing the more fundamental mechanism. “What we have to do is maintain interpersonal relationships,” Sandel told Scientific American. “If we can reunite — even in the face of conflict — then I think that’s a recipe for maintaining peace.” Liran Samuni of the German Primate Center, who was not involved in the study, noted that even before the split, the Ngogo community was “one of the chimpanzee communities that was most violent in terms of encroaching on neighbors” — they had previously killed at least 21 chimpanzees from other groups and expanded into their territory. The civil war is new. The violence isn’t.

    The Gombe parallel

    Anne Pusey, who conducted fieldwork at Gombe until 1975 during the beginning of that war, told the Washington Post that the circumstances preceding both conflicts were “similar and shocking”: a shortage of mating-age females, the death of socially central older males, a change in alpha male, and disease. In both cases, social bonds that had been stable for years degraded rapidly once key connective individuals were removed from the network. Joseph Feldblum, an evolutionary anthropologist who has studied the Gombe data, said the Ngogo findings validate the earlier observations: “This sort of behavior, while rare, is part of the natural course of chimpanzee behavior.”

    The baboon politics research on coalition formation and dominance hierarchies, the chimpanzee tool use literature documenting cultural transmission across generations, and the dolphin signature whistle work demonstrating individual identity in non-human social systems all converge on the same insight the Ngogo war makes visceral: complex social cognition isn’t an abstract capacity. It’s the infrastructure that holds societies together — and when the infrastructure fails, the consequences in chimpanzee communities look disturbingly like the consequences in human ones. Former friends become lethal enemies not because something changed about who they are, but because the relationships that made them “us” instead of “them” stopped being maintained.

    We cover the Ngogo war alongside mirror neurons, corvid intelligence, animal deception, and 20 other investigations into what animal minds reveal about the architecture of social life across our Animal Culture & Knowledge course — where the question isn’t whether animals have societies but what happens when those societies break.

  • Deception in Animals: Which Species Lie and What That Tells Us About Cognition

    A male mourning cuttlefish wants to mate with a female. A rival male is watching. The cuttlefish does something that should be impossible for a creature with a 10-month lifespan and no social upbringing: he splits his body display in half. On the side facing the female, he shows courtship coloration — bright, patterned, unmistakably male. On the side facing the rival, he simultaneously displays female patterning — muted, cryptic, a disguise designed to convince the rival that no competition is present. Two contradictory signals, broadcast from one body, targeted at two different audiences at the same time. That’s not camouflage. That’s not instinct in any simple sense. That’s an animal producing a lie calibrated to two different observers with two different perspectives, and executing it in real time with chromatophores instead of words.

    The question of whether animals deceive each other is settled — they do, constantly, across hundreds of species. The question that matters is what kind of deception they’re performing, because the answer tells you something fundamental about what’s happening inside their nervous systems. And a May 2025 paper in Trends in Ecology & Evolution by Drerup, Garcia-Pelegrin, Clayton, and colleagues just reframed the entire field by proposing cephalopods — not primates, not corvids — as the ideal model organisms for studying the most cognitively demanding form of deception.

    The spectrum

    Not all deception is created equal, and the distinctions matter more than the examples. At the bottom of the spectrum, you have deception that requires no cognition at all. Harmless butterflies evolving wing patterns that mimic toxic species is deception — it communicates false information to predators — but nobody claims the butterfly is “lying.” The misinformation is encoded genetically over evolutionary time, not produced by an individual making a decision. A stick insect that looks like a twig is deceiving every bird that passes without doing anything except existing. This is deception without a deceiver.

    One step up, you get deception that involves behavioral flexibility but may still be conditioned rather than cognitively strategic. Firefly femmes fatales — females of the genus Photuris that mimic the flash patterns of Photinus females to lure Photinus males close enough to eat them — produce species-specific flash codes that attract prey. The behavior is adaptive, it’s flexible (the predator adjusts flash timing to match different prey species), but it may operate through relatively simple learning mechanisms rather than any representation of what the victim “believes.”

    At the top sits tactical deception — deceptive behavior that is flexibly adjusted based on the identity, perspective, or inferred knowledge of the observer. This is the category that implies something approaching theory of mind, the capacity to understand that another individual’s knowledge or perspective differs from your own and to exploit that asymmetry. Tactical deception has been documented primarily in two vertebrate groups: primates and corvids.

    The primate evidence

    Primates are the best-studied tactical deceivers. Research across 18 species has demonstrated a strong correlation between the frequency of tactical deception and the size of the neocortex — suggesting that the capacity to deceive conspecifics was itself a selection pressure driving brain evolution, a hypothesis known as the Machiavellian intelligence theory. Chimpanzees suppress food calls when dominant individuals are nearby, concealing discoveries rather than sharing them. Subordinate males lead dominant rivals away from hidden food by walking confidently in the wrong direction, then doubling back to retrieve it when the dominant is out of sight. Baboons have been observed using false alarm calls — predator warnings issued when no predator exists — to scatter competitors away from food resources.

    The key distinction is context-dependence. A chimpanzee doesn’t suppress every food call — she suppresses them selectively, when a specific dominant individual is present and when the social cost of sharing outweighs the benefit. The behavior varies with audience, which means the animal is tracking who knows what, who can see what, and what the consequences of being detected are. Whether that constitutes genuine “mind-reading” or a sophisticated learned association between behavioral cues and outcomes is the debate that has occupied comparative cognition researchers for decades. The behavior looks like theory of mind. Proving it is theory of mind rather than behaviorally flexible conditioning is extraordinarily difficult, because the observable output is identical.

    The corvid evidence

    Corvids — jays, ravens, crows — match primates in deceptive sophistication despite being separated by 320 million years of evolution. Nicola Clayton’s lab at Cambridge has produced some of the field’s most striking results. Western scrub-jays that have been observed caching food by another jay will return later, when the observer is absent, and re-cache the food in a new location — but only if the cacher has personal experience of having stolen food from others. Jays that have never stolen don’t re-cache. The implication is that the cacher is projecting its own experience of thievery onto the observer — reasoning, in effect, “I would steal from that cache, so this jay probably will too.”

    Ravens observed by Thomas Bugnyar show similar patterns. They monitor the gaze direction of competitors during caching events and adjust their concealment strategies based on whether they believe the competitor has visual access to the cache location. A 2016 study demonstrated that ravens can track whether an observer can see through a peephole — adjusting their caching behavior based on whether the peephole is open or closed, even when no actual observer is present. The researchers argued this showed an understanding of another’s visual perspective independent of behavioral cues, though the interpretation remains contested.

    Garcia-Pelegrin’s work at Cambridge has added another dimension: using magic tricks as experimental tools. Jays were shown sleight-of-hand coin vanishes and real transfers. The birds tracked the real transfers accurately but were fooled by the sleights — demonstrating that they form predictions about object permanence and manual actions that can be violated, just as human audiences are fooled by the same techniques. The cognitive architecture that makes you susceptible to a magic trick is the same architecture that allows you to deceive others.

    The cephalopod frontier

    The 2025 Drerup et al. paper in Trends in Ecology & Evolution argues that cephalopods — octopuses, cuttlefish, and squid — are the ideal organisms for studying tactical deception because they combine two things no other taxon offers at the same scale: an extraordinarily rich behavioral repertoire of naturalistic deception and cognitive abilities sophisticated enough to potentially support flexible, audience-dependent deployment.

    The mourning cuttlefish’s split-body display is the poster case, but it’s not the only one. Common cuttlefish flash false eyespots to scare approaching predators — but only to visually oriented predators, not to those that hunt by smell, suggesting the behavior is calibrated to the sensory capabilities of the audience. Giant Australian cuttlefish males that are too small to win fights adopt female coloration and posture to sneak past rival males and access females — a transient, context-dependent mimicry that is abandoned the moment the social environment changes. Female opalescent squid mimic male appearance by flashing a white stripe to deter unwanted mating attempts, deploying the deception only under specific conditions.

    The critical question the paper raises is whether these behaviors constitute conditioning — learned responses to specific cue-outcome pairings — or tactical deception, which requires the deceiver to evaluate information about the observer and adapt its strategy based on the observer’s perspective. The distinction matters because cephalopods have nervous systems organized completely differently from vertebrates — 500 million neurons in an octopus, most distributed across peripheral ganglia in the arms rather than concentrated in a central brain. If cephalopods perform tactical deception, it evolved independently from the primate and corvid lineages, through entirely different neural architecture, which would tell us something profound about what kinds of nervous systems can support perspective-taking and flexible social cognition.

    What deception tells us about minds

    The ability to lie is — paradoxically — one of the strongest indicators of cognitive sophistication. A truthful signal requires only a detection system and a broadcast mechanism. A deceptive signal requires, at minimum, a model of what the receiver expects, an ability to generate a signal that violates reality while matching that expectation, and — in the case of tactical deception — a capacity to adjust the deception based on who’s watching. Every step up the deception spectrum adds a layer of cognitive complexity that brings the deceiver closer to what we’d recognize as a mind.

    The convergent evolution of tactical deception in primates, corvids, and potentially cephalopods — three lineages separated by hundreds of millions of years and running on radically different neural hardware — suggests that the capacity for deception isn’t a quirk of primate brains. It’s a solution that evolution converges on whenever social complexity creates enough pressure to make manipulating others’ behavior worth the cognitive investment. The cuttlefish that splits its body display between two audiences and the chimpanzee that leads a rival away from hidden food are solving the same problem with different equipment. The problem is other minds. The equipment is whatever nervous system natural selection had to work with.

    We cover deception alongside mirror neurons, dolphin naming, tool use, and 20 other investigations into what animal nervous systems can do across our Animal Culture & Knowledge course — where the question isn’t whether animals have minds but what kind of minds they have, and how we’d know.

  • Orangutan Self-Medication: How Great Apes Choose Plants to Treat Their Own Wounds and Infections

    On June 22, 2022, researchers at the Suaq Balimbing research station in Sumatra’s Gunung Leuser National Park heard a series of long calls from the canopy—the vocalizations male orangutans produce during dominance confrontations. The next day, they noticed that a flanged male orangutan named Rakus had a fresh wound on his right cheek, just below the eye, probably from a fight with a neighboring male. Three days later, they watched him do something no wild animal had ever been documented doing: he selected a specific plant—a climbing vine called Fibraurea tinctoria, known locally as Akar Kuning—ripped off its leaves, chewed them for 13 minutes, and then spent seven minutes applying the resulting juice directly to his wound with his fingers. He didn’t swallow the leaves during the application phase. When flies began landing on the wound, he covered it entirely with the chewed plant material, creating a poultice. The next day, he returned to the same plant and ate more leaves. Within five days, the wound closed. By July 19—roughly a month after the injury—only a faint scar remained. No infection developed.

    The paper, published in Scientific Reports in May 2024 by Isabelle Laumer and Caroline Schuppli of the Max Planck Institute of Animal Behavior, called it “the first known case of active wound treatment in a wild animal with a medical plant.” The emphasis on “active” is deliberate. Animals have been observed swallowing plants with medicinal properties before—chimpanzees chew bitter pith, gorillas and bonobos swallow rough leaves whole to mechanically dislodge intestinal parasites, Bornean orangutans rub chewed plants on their limbs. But those behaviors involve ingestion or generalized application. What Rakus did was topical, targeted, and sequential: he applied the plant’s juice specifically to the wound, on no other body part, repeated the application multiple times, and then covered the wound with plant material. He treated his own injury the way a human would treat a cut—clean it, apply medicine, bandage it.

    Why Akar Kuning matters

    Fibraurea tinctoria is not a random plant. It’s a climbing liana found across Southeast Asia—Indonesia, Malaysia, Thailand, Vietnam—and it’s used extensively in traditional medicine to treat dysentery, diabetes, malaria, and infections. Chemical analysis of the plant has identified furanoditerpenoids and protoberberine alkaloids with documented antibacterial, anti-inflammatory, antifungal, antioxidant, and analgesic properties. The plant also contains jatrorrhizine, which has antimicrobial and anticancer properties, and palmatine, which has anti-inflammatory and antiviral effects. This isn’t a plant that happens to have healing properties. It’s a plant whose healing properties are well-characterized enough that humans have been using it medicinally for centuries.

    Rakus’s population at Suaq Balimbing rarely eats it. In 21 years and roughly 390,000 feeding observations at the site, Fibraurea tinctoria appeared in only 0.3 percent of feeding scans. This wasn’t a plant the orangutan was already eating when he happened to touch his wound. He selected it specifically, used it in a way that doesn’t correspond to normal feeding behavior, and applied it exclusively to the injury. The researchers were careful to note that in 21 years and 28,000 observation hours, they had never previously seen an orangutan use leaves to treat a wound.

    How deliberate was it?

    This is the question the paper addresses directly and honestly. The behavior appeared intentional: Rakus selectively treated only his facial wound, not other body parts. He repeated the application multiple times. He used both the juice (liquid application) and the solid plant material (poultice). The entire process—feeding on the plant, applying the juice, covering the wound—took a considerable amount of time and was sustained across two consecutive days. The sequence is difficult to explain as accidental.

    But the researchers offer two possible origin stories, and they’re transparent about not being able to distinguish between them. The first is “accidental individual innovation”—Rakus may have been feeding on the plant, accidentally touched his wound while chewing, felt immediate pain relief from the plant’s analgesic effects, and then repeated the behavior because it worked. Under this model, the behavior was discovered by accident and reinforced by its consequences, which is how a lot of animal tool use and self-medication originates. The second possibility is social learning—Rakus wasn’t born at Suaq Balimbing. Male orangutans disperse from their natal area during or after puberty, sometimes traveling long distances. Rakus may have observed the behavior in his birth population, carried the knowledge across dispersal, and applied it when the situation required. If so, the behavior represents a cultural tradition transmitted between individuals, not an individual invention.

    The researchers can’t determine which explanation is correct because they don’t know where Rakus was born or what behaviors are practiced in that unknown population. This ambiguity is frustrating but honest—and it’s the central challenge of studying animal self-medication in the wild. You’re observing rare behaviors in long-lived animals across vast landscapes with limited coverage, and the most interesting questions (was it invented or learned?) require data from populations you may never have access to.

    The broader landscape of animal self-medication

    Rakus’s wound treatment is the most dramatic documented case, but self-medication in animals—zoopharmacognosy—is a recognized field with decades of evidence across multiple species and continents.

    Chimpanzees at multiple African field sites chew the bitter pith of Vernonia amygdalina, a plant with antiparasitic compounds, when they’re suffering from intestinal infections. The behavior is targeted: chimps eat it when sick and avoid it when healthy, suggesting they’re responding to internal cues rather than eating it as a regular food. Gorillas, chimpanzees, and bonobos swallow rough, hairy leaves from Aspilia and other plants whole and without chewing—the leaves pass through the digestive tract intact and physically dislodge intestinal parasites, which researchers have confirmed by examining fecal samples and finding parasites wrapped in leaf material. This is mechanical self-medication: the plant’s physical properties, not its chemistry, provide the therapeutic effect.

    Bornean orangutans have been observed rubbing chewed leaves of Dracaena cantleyi on their limbs, producing a lather that may have anti-inflammatory or antiparasitic properties. Capuchin monkeys rub citrus fruits and certain plants on their fur, potentially as insect repellent. Some moth species lay their eggs on alkaloid-rich plants when infected by parasitoid wasps, effectively medicating their offspring by ensuring the larvae consume antiparasitic compounds. Even fruit flies preferentially consume alcohol-containing food when infected by parasitoid wasps—the ethanol kills the wasp larvae developing inside them.

    The pattern across these examples is consistent: animals with no understanding of chemistry, pharmacology, or infection select specific substances with specific biological activity in response to specific health conditions. The behavior isn’t random foraging. It’s condition-dependent, substance-specific, and in many cases targeted to the affected body region. The question isn’t whether animals self-medicate. They do. The question is what cognitive mechanism enables it.

    What it means for the origins of medicine

    The earliest known human medical manuscript, from Mesopotamia around 2200 BCE, describes wound treatment with plant-based remedies. But if a Sumatran orangutan—separated from the human lineage by roughly 14 million years of evolution—independently applies a biologically active plant to a wound and covers it with a poultice, the implication is that the cognitive capacity for wound treatment predates the human lineage entirely. Laumer and Schuppli suggest that “medical wound treatment may have arisen in a common ancestor shared by humans and orangutans,” and that the behavior observed in Rakus may reflect deep evolutionary roots rather than a recent invention.

    The alternative—that Rakus and the Mesopotamian scribe independently arrived at the same solution—is possible but requires the same cognitive prerequisites: recognizing that a wound needs treatment, selecting a substance with appropriate properties, applying it specifically to the injury, and sustaining the behavior long enough for healing to occur. Whether the common ancestor had this capability or whether it evolved convergently in hominids and orangutans, the conclusion is the same: medicine didn’t start with humans. It started with primates who paid attention to what made them feel better and repeated it.

    Traditional healers in Indonesian Borneo have reportedly learned plant-based remedies by observing orangutan behavior—the knowledge transmission running from ape to human rather than the reverse. If Rakus learned his wound treatment from his natal population, and if human populations learned similar treatments from watching orangutans, then the same medicinal knowledge has been transmitted across species boundaries in both directions. The forest pharmacy has always been open. The question is who figured out the inventory first.

    We cover orangutan self-medication alongside baboon politics, ant collective intelligence, and the full landscape of animal cognition across our Animal Culture & Knowledge course—including why the first pharmacist may not have been a person. It may have been a primate with a cheek wound and the sense to reach for the right vine.

  • Pigeons That Read X-Rays: The Experiment That Proved Birds Can Spot Breast Cancer

    In 2015, pathologist Richard Levenson at UC Davis and psychologist Edward Wasserman at the University of Iowa put 16 pigeons in individual chambers, each containing a touchscreen displaying digitized breast tissue biopsies. On either side of the image were two colored buttons—one for benign, one for malignant. If the pigeon pecked the correct button, a computer automatically dispensed a 45-milligram food pellet. If it pecked wrong, nothing happened. No humans were visible during training—the entire process was automated to avoid the Clever Hans effect, where animals appear to reason but are actually reading subtle cues from their handlers.

    Within 15 days, individual pigeons were identifying cancerous breast tissue at 85 percent accuracy. When the researchers combined the responses of four birds in a “flock-sourcing” approach—taking the majority answer—accuracy climbed to 99 percent. That’s on par with trained human pathologists.

    The pigeons weren’t memorizing slides. When shown completely novel images they’d never encountered—different tissue samples, different magnifications, different degrees of image compression, images with and without color—they generalized successfully. They had learned to detect the visual features that distinguish malignant from benign tissue, not to associate specific images with specific rewards. A bird that had never attended medical school, that has no concept of cells or cancer or pathology, was reading histological slides with the diagnostic accuracy of a specialist who trained for a decade.

    What they could do and what they couldn’t

    The pigeons’ performance wasn’t uniform across all tasks, and the boundaries of their ability tell you as much as their successes.

    Histopathology—digitized microscope slides of breast tissue biopsies—was where they excelled. They learned fast, generalized to novel images, and handled variations in magnification (4x, 10x, 20x) and image quality. Wasserman, who had studied pigeon cognition for over 40 years, said they learned to discriminate benign from malignant tissue as fast as pigeons in any other visual discrimination study his lab had ever conducted. The task wasn’t easy for humans—inexperienced human observers require considerable training to reach mastery on the same slides—but the pigeons picked it up in days.

    Mammographic microcalcifications—the tiny calcium deposits that, in certain configurations, indicate breast cancer—were a second success. These appear as patterned white specks against a complex background on mammograms, and the researchers hypothesized that detecting small bright targets in visual clutter is precisely the kind of task pigeons evolved to perform. Finding seeds in grass, finding microcalcifications on a mammogram—structurally, the visual problem is similar. The pigeons could detect microcalcifications on novel mammograms they hadn’t seen during training.

    Mammographic masses—the suspicious tissue densities that can signal cancer but lack the discrete visual signature of microcalcifications—were where the pigeons hit their ceiling. Human radiologists achieve about 80 percent accuracy on these images, which are genuinely difficult even for trained professionals. The pigeons took weeks instead of days to learn the training set, and when shown novel images, they performed at chance. They had memorized the specific masses in the training images without extracting the generalizable features—the stellate margins, the irregular borders, the density patterns—that correlate with malignancy. They could learn the specific. They couldn’t learn the abstract.

    This boundary matters because it reveals the architecture of what the pigeons are doing. They’re not reading X-rays the way a radiologist reads them—constructing a clinical interpretation from visual features informed by anatomical knowledge and diagnostic frameworks. They’re performing pattern recognition at a level that is, for certain categories of visual stimuli, extraordinarily sophisticated, and for other categories, completely absent. The pigeon has no concept of cancer. It has a visual system that, after millions of years of evolutionary optimization for detecting meaningful patterns in complex environments, can be trained to recognize the visual signatures of pathology on a slide faster than a medical student can.

    Why pigeons see what they see

    Pigeons have tetrachromatic vision—four types of color receptors compared to humans’ three—and their visual acuity, while not as fine-grained as humans’ for detail at a distance, is optimized for detecting patterns, textures, and small differences across complex visual fields. They can discriminate individual human faces, distinguish paintings by Monet from paintings by Picasso, and categorize photographs of objects they’ve never seen into previously learned categories. Their visual cognition is not simple stimulus-response association. It involves genuine perceptual categorization—the extraction of abstract features that define a class and the application of those features to novel instances.

    The pigeon brain processes visual information through a pathway called the tectofugal system, which is analogous but not homologous to the mammalian cortical visual pathway. The computational result is similar—pattern extraction, categorization, generalization—but achieved through different neural architecture. This is convergent evolution at the cognitive level: two lineages separated by over 300 million years of evolution arriving at functionally equivalent solutions to the same problem, which is making sense of a visually complicated world.

    The cancer detection experiment wasn’t really about cancer. It was about visual cognition. Levenson, Wasserman, and their colleagues were using medical imaging as a standardized, well-characterized visual discrimination task to probe the capabilities and limits of pigeon perception. The fact that the visual stimuli happened to be diagnostically important—that the patterns the pigeons were detecting are the same patterns that determine whether a patient gets a biopsy or goes home—is what made the study irresistible to the public. But the scientific contribution was the demonstration that pigeon visual cognition can be meaningfully compared to human expert performance on the same images, using the same accuracy metrics.

    The practical question nobody expected

    Levenson was clear that pigeons are not going to replace radiologists. The regulatory implications alone—”What would the FDA think about pigeons?” he said, “I shudder to think”—make clinical deployment a nonstarter. And for the visual tasks where human expertise is most critical—the ambiguous masses, the complex densities, the cases where clinical context determines interpretation—the pigeons failed.

    But the practical application isn’t diagnosis. It’s quality assurance. Medical imaging technology is constantly evolving—new display technologies, new compression algorithms, new processing pipelines, new acquisition hardware—and every innovation needs to be validated by trained observers who evaluate whether the new system makes diagnostically important features easier or harder to see. That validation currently requires recruiting clinicians to spend hours or days doing tedious comparisons of image sets, a process that is expensive, slow, and dependent on the availability of people who have better things to do with their medical training.

    Pigeons don’t get bored. They don’t get fatigued. They don’t have clinic schedules or grant deadlines. They can evaluate thousands of images without the performance degradation that affects human observers after prolonged sessions. For the subset of visual tasks where pigeon accuracy matches or approaches human accuracy—histopathology slides, microcalcification detection—pigeons could serve as a rapid, cheap, reliable feedback system for the engineers building better imaging tools. Levenson suspects computers will get there first, and given the trajectory of AI-based image analysis since 2015, he’s probably right. But for a decade, the pigeons were competitive.

    What it actually tells us

    The deeper lesson of the pigeon cancer experiment isn’t about medicine or about pigeons. It’s about what vision is. A pigeon with a brain the size of a walnut, a lifespan during which it will never encounter a microscope or learn what a cell is, can be trained to perform a visual discrimination task that humans require years of specialized education to master. This means the visual features that distinguish malignant from benign tissue are not visible only to minds that understand cancer. They’re visible to any sufficiently powerful pattern recognition system—biological or computational—that can be calibrated against enough examples.

    The pigeon doesn’t know what it’s looking at. It doesn’t need to. The visual signal is in the image. The pigeon’s 300-million-year-old visual system just happens to be good enough to find it.

    We cover pigeon visual cognition alongside baboon politics, cuttlefish camouflage, and the full landscape of animal intelligence across our Animal Culture & Knowledge course—including why a bird that can’t tell you what cancer is might still be better at spotting it than a first-year medical resident.

  • Baboon Politics: Social Hierarchies, Alliances, and Machiavellian Intelligence in Primates

    A baboon can do something that most humans find cognitively demanding and many find socially impossible: induce a more powerful individual to attack a third party on its behalf, without the powerful individual realizing it’s being used as a weapon. The maneuver is called a “protected threat.” The baboon appeases the dominant member of its group, positions itself to make a subordinate appear threatening, and maneuvers to prevent the target from doing the same thing in reverse. It’s social tool use—using another organism as an instrument to achieve a goal—and baboons master it at puberty. Chimpanzees, by comparison, don’t learn to use a stone to crack nuts until adulthood. Primates appear to manipulate social objects with more sophistication and at earlier developmental stages than physical tools, which raises an uncomfortable question about what primate brains actually evolved to do.

    The answer, according to a hypothesis that has shaped comparative cognition for nearly four decades, is politics.

    The Machiavellian intelligence hypothesis

    In the 1960s, lemur researcher Alison Jolly noticed something counterintuitive. Lemurs were terrible at manipulating objects—far worse than monkeys at the mechanical problem-solving tasks that laboratories used to measure intelligence. But their social skills were just as sophisticated as monkeys’. Jolly proposed reversing the common assumption: instead of social complexity being a product of intelligence, intelligence might be a product of social complexity. The technical challenges of foraging—finding food, processing it, remembering where it grows—might matter less than the social challenges of living in permanent groups with dozens of individuals who are simultaneously your allies, rivals, mates, competitors, and kin.

    Psychologist Nicholas Humphrey extended this in 1976. He’d watched captive monkeys handle laboratory puzzles with impressive skill, but he couldn’t find anything comparably challenging in their natural foraging environment. The hardest problem these animals faced, he argued, wasn’t physical. It was social—navigating a group where every interaction involved weighing cooperation against competition, tracking who owes what to whom, remembering past conflicts and predicting future alliances, and doing all of this with individuals who are simultaneously doing the same calculations about you.

    Frans de Waal’s 1982 book Chimpanzee Politics documented the social maneuvering of chimpanzees in terms that read like a dispatch from the Florentine court—coalition formation, strategic alliance shifts, betrayals, reconciliations, and the systematic deployment of social favors as a form of political currency. Andrew Whiten and Richard Byrne formalized the concept in 1988 as the Machiavellian intelligence hypothesis: the pressure to outmaneuver other members of your social group is a primary driver of the evolution of primate intelligence. The brain got bigger not because the environment got harder but because the social group got more complicated.

    Robin Dunbar demonstrated a correlation between primate group size and neocortex size—the most recently evolved part of the brain, and the part that expanded most dramatically in the primate lineage compared to other mammals. Larger groups require tracking more relationships, remembering more histories, predicting more behaviors. The cognitive load scales with the number of social connections, not with the complexity of the physical environment. Primates have brains roughly twice as large as expected for mammals of equivalent body size, and the Machiavellian intelligence hypothesis argues that social computation—not tool use, not foraging, not predator avoidance—is the primary reason.

    What baboons actually do

    Baboon troops are not democracies. They’re hierarchies maintained through a combination of aggression, alliance formation, grooming, and the careful management of social relationships that function as a currency more stable than any physical resource. Male baboons compete for rank through direct confrontation, but rank alone doesn’t determine reproductive success. Males who form alliances—particularly with unrelated males—can collectively outcompete higher-ranking individuals. The alpha male is not always the most reproductively successful male. The most politically connected male sometimes is.

    Female baboons form their own hierarchies, typically more stable than male hierarchies and based heavily on kinship. A female’s rank often follows her mother’s, creating lineages of dominant and subordinate families that persist across generations. High-ranking females get better access to food and water, experience lower stress hormone levels, and have offspring with higher survival rates. The fitness consequences of social rank are measurable, heritable, and real.

    Grooming is the central social technology. Baboons groom each other for hours daily, and the distribution of grooming is not random. It correlates with alliance patterns, kinship, and—critically—with what the grooming partner can offer in the immediate social marketplace. Research on wild chacma baboons found that female coalitions were not long-term strategic alliances built through reciprocal grooming over months. They were opportunistic, short-term transactions where both parties benefited immediately. Baboons don’t trade favors across time the way the Machiavellian framework originally suggested. They trade in real time, in a social marketplace where the value of a grooming partner fluctuates based on current social conditions.

    This finding—published by Silk, Cheney, Seyfarth, and others—complicated the original hypothesis significantly. The Machiavellian framework emphasized long-term strategic planning, deception, and reciprocal exchange. The field data suggested something more like a spot market: baboons assessing the current value of social partners and adjusting their behavior accordingly, not executing multi-step schemes that require remembering who did what three weeks ago.

    Tactical deception

    Byrne and Whiten documented tactical deception in baboons—behaviors designed to create false impressions in the minds of other individuals. A subordinate baboon feeding on a preferred food item while a dominant individual approaches will sometimes casually move away from the food and adopt a relaxed posture, as if it had finished eating or hadn’t been eating at all. Once the dominant passes, the subordinate returns to the food. The behavior requires, at minimum, an understanding that the dominant’s behavior is influenced by what it believes about the subordinate’s behavior—a rudimentary form of the social cognition that in humans we’d call theory of mind.

    Mountain gorillas suppress their copulation vocalizations during secretive matings with subordinate males, conducted out of sight of the dominant silverback. Both the female and the junior male remain silent—a coordinated deception that requires both parties to understand that the dominant male’s response depends on what he perceives. When these matings are discovered, the dominant male invariably attacks the female, adding a punitive dimension to the social calculation: the cost of being caught is asymmetric, falling more heavily on the female, which means the decision to mate secretly involves weighing the reproductive benefit against a gendered risk of punishment.

    Dario Maestripieri at the University of Chicago, studying rhesus macaques, found that these monkeys share with humans “strong tendencies for nepotism and political maneuvering.” His conclusion: “Our Machiavellian intelligence is not something we can be proud of, but it may be the secret of our success.” The cognitive machinery that enables a baboon to manipulate a dominant individual into attacking a rival may be the same machinery that, scaled up and elaborated over millions of years, enables a human to navigate corporate politics, negotiate a trade deal, or run for office.

    What the critics found

    The Machiavellian intelligence hypothesis has generated productive pushback. Barrett and Henzi, studying baboons and other primates in the field, argued that the hypothesis overemphasizes exploitation and deception at the expense of tolerance, coordination, and cooperation. Primate social life, they contended, is not primarily a chess game of strategic manipulation. It’s “an intricate tapestry of competition and cooperation, of aggression and reconciliation, of nonaggressive social alternatives, and of behaviors and relationships that cannot be easily categorized into simple opposites.”

    The orangutan problem is frequently cited: orangutans are largely solitary but outperform the highly social baboon on cognitive tests. If social complexity drives intelligence, the most social species should be the smartest. They’re often not. The relationship between sociality and cognition is real but messier than the original hypothesis suggested—group size correlates with neocortex size across the primate order, but individual species frequently violate the pattern.

    The current consensus treats the Machiavellian intelligence hypothesis as an important partial explanation rather than a complete theory. Social complexity is a major driver of primate brain evolution, but it’s not the only driver, and the specific form that social cognition takes—long-term strategic planning versus real-time marketplace trading, deceptive manipulation versus cooperative coordination—varies between species in ways the original framework didn’t predict.

    Why it matters beyond primatology

    The baboon troop is a small-scale version of the problem every human organization faces: how do you maintain a stable group when every member has individual interests that partially conflict with the group’s interests? The baboon’s solution set—hierarchy, coalition, grooming, deception, reconciliation, punishment, nepotism—is recognizable to anyone who has spent time in a corporate office, a political party, or a homeowners association. The specifics differ. The architecture doesn’t.

    The deeper implication is about what brains are for. If the Machiavellian intelligence hypothesis is even partially correct, the enormous human neocortex didn’t evolve primarily to solve physics problems or build tools or develop language. It evolved to navigate other humans—to predict what they’ll do, influence what they think, form alliances that advance your interests, and detect when someone is doing the same to you. The math, the engineering, the art, the philosophy—all of it may be a secondary application of cognitive hardware that was built, under evolutionary pressure, for politics.

    We cover baboon social intelligence alongside chimpanzee tool traditions, dolphin communication, and the full landscape of animal cognition across our Animal Culture & Knowledge course—including why the most revealing thing about human intelligence might be how much of it we share with a monkey that learned to weaponize its friends.

  • Fish That Use Tools: The Species That Shattered Assumptions About What Fish Can Do

    In 2006, a diver named Scott Gardner was ascending from an 18-meter dive in the Keppel Islands region of the Great Barrier Reef when he heard a cracking noise. He looked over and saw a blackspot tuskfish hovering above a sand patch, holding a cockle shell in its jaws. The fish was rolling onto its side and slamming the shell against a rock—alternating left and right blows, aimed at the pointed section of the rock for maximum impact—until the shell cracked open. Scattered around the rock were broken shells from previous meals. This wasn’t an isolated event. It was a feeding station. The fish had a preferred anvil, and it had been using it long enough to accumulate a midden of shattered prey.

    Gardner photographed the sequence. The images were published in Coral Reefs in 2011, and the paper posed a question in its title that a generation of biologists had considered already answered: “Tool use in the tuskfish?” The question mark was doing heavy lifting. By the definitions that Jane Goodall had established—the use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal—the tuskfish was using a tool. The external object was the rock. The goal was food. The behavior was deliberate, sequential, and repeated. The only reason anyone hesitated to call it tool use was that the animal doing it was a fish.

    Why this matters more than it should

    For most of the history of comparative cognition, the assumption was straightforward: fish are simple. They operate on instinct. They have small brains, short memories, and minimal behavioral flexibility. Tool use—the cognitive capacity to identify an external object, recognize its functional utility, and deploy it to achieve a goal—was reserved for the clever animals: primates, corvids, maybe elephants and sea otters. The hierarchy was implicit and rarely questioned. Mammals and birds think. Fish react.

    The tuskfish broke that hierarchy not by being unusually smart but by doing something that forced the definition of intelligence to either expand or become incoherent. If tool use is a marker of advanced cognition, and a fish uses tools, then either the fish is cognitively advanced or tool use isn’t the marker we thought it was. Both conclusions are uncomfortable for the framework that produced the hierarchy in the first place.

    The discomfort deepened as evidence accumulated. The tuskfish observation wasn’t a one-off. A 2025 study led by Macquarie University, published in Coral Reefs, documented anvil use in five species of Halichoeres wrasses across the western Atlantic—the first evidence of tool use for three of those species and the first video evidence for the other two. Through a citizen science initiative, researchers gathered 16 new observations of wrasses deliberately picking up hard-shelled prey and smashing them against rocks, corals, and other hard surfaces. The findings extended the known range of fish tool use from the Indo-Pacific to the Atlantic and from a handful of isolated observations to a pattern distributed across an entire fish family spanning 50 million years of evolution.

    Culum Brown, head of the Fish Lab at Macquarie University and one of the foremost researchers on fish cognition, suggested that wrasses may be fishes’ answer to primates among mammals and corvids among birds—a lineage with a disproportionate number of examples of cognitive complexity relative to the broader group. Researchers at the Paris-Saclay Institute of Neuroscience found that wrasses have a larger telencephalon and forebrain region compared to other teleost fish, including a substantially enlarged inferior lobe—a brain structure with no direct analog in mammals or birds—that shows unique connectivity to the pallium, a region already linked to higher-order cognition in other animals.

    The physics problem fish solved

    The reason tool use is rare in fish isn’t necessarily cognitive. It’s physical. Water is 800 times denser than air. Try swinging a hammer underwater and you’ll understand the constraint immediately. The momentum required to crack a shell with an object held in your mouth, while suspended in a fluid medium that resists rapid movement in every direction, is orders of magnitude harder to generate than doing the same thing on land. A chimpanzee cracking a nut with a rock is operating in an environment that cooperates with the physics of impact. A fish is operating in an environment that actively resists it.

    The tuskfish solved this by inverting the relationship: instead of swinging a tool against a stationary target, it swings the target against a stationary tool. The rock is the anvil, fixed in the substrate. The shell is the projectile, gripped in the fish’s jaws and slammed against the anvil through rapid body rotation. This isn’t just tool use. It’s tool use adapted to an environment where the conventional approach—wielding a hammer—is physically impossible. The fish engineered a workaround.

    The sixbar wrasse took the same approach in captivity. Given food pellets too large to swallow and too hard to break with its jaws, the wrasse carried the pellets to a rock in its aquarium and smashed them. The researcher who observed it, Łukasz Paśko at the University of Wrocław, watched the wrasse perform the behavior 15 times and described it as “remarkably consistent” and “nearly always successful.” The behavior only appeared after many weeks in captivity, suggesting the fish learned it through individual experience rather than instinct—it tried other approaches first, found them inadequate, and developed a new strategy.

    Anvils, middens, and long-term site fidelity

    A 2023 study on graphic tuskfish in New Caledonia found that specific anvils showed evidence of being used by one or more tool-using fish for years. The anvils accumulated debris. Other fish species learned to recognize the visual and auditory cues of tool use in progress—the body movements, sand clouds, and the “clack” sound of shell hitting rock—and gathered as scavengers. In 94 percent of observed tool-use events, attendant fish from six different families showed up to pick up fragments: surgeonfishes, triggerfishes, butterflyfishes, wrasses, angelfishes, and damselfishes. The tuskfish’s tool use had created a micro-ecosystem around its feeding station—a social and ecological structure generated by a fish banging a clam on a rock.

    The wrasses also showed flexibility in their tool use, selecting different types of anvils for different prey and sometimes switching anvils mid-session when the first choice wasn’t working. This isn’t stereotyped behavior—the kind of fixed action pattern that “instinct” describes. It’s decision-making under uncertainty, adapted in real time to the properties of the specific prey item and the available tools.

    The archerfish problem

    The wrasses aren’t the only fish that complicate the tool-use question. Archerfish—four-inch tropical marksmen from estuaries and mangroves between India and the Philippines—hunt by shooting precisely aimed jets of water at insects sitting on vegetation above the water’s surface, knocking them into the water where they can be eaten. The archerfish accounts for refraction at the water’s surface, adjusts for the target’s distance and position, and can hit prey up to three meters above the waterline. Researchers have demonstrated that archerfish can learn to recognize human faces and can be trained to hit specific targets, showing a capacity for visual discrimination and precision that wouldn’t be out of place in a primate cognition lab.

    Whether the water jet constitutes a “tool” depends on how strictly you define the term. The archerfish isn’t wielding an external object—it’s producing a projectile from its own body, more analogous to a spider’s web than a chimpanzee’s stick. But the functional outcome is the same: an organism using a mechanism beyond its own body to obtain food that would otherwise be inaccessible. The boundary between tool and technique blurs when the organism in question can’t hold anything in its hands, because it doesn’t have hands.

    What 600 species of wrasse haven’t told us yet

    There are over 600 species of wrasses worldwide. The Macquarie University team’s citizen science initiative is explicitly calling for divers and snorkelers to report observations of anvil use, acknowledging that the documented cases almost certainly represent a fraction of the actual prevalence. Brown put it directly: “For a long time, tool use was thought to be exclusive to primates and birds. We are still far from knowing how many species of wrasses use tools.” The field of fish cognition itself is young—69 percent of published studies used captive-reared subjects, only 9 percent conducted experiments on wild fish in their natural environment—meaning we’ve been studying fish cognition primarily by watching captive fish in artificial environments and then drawing conclusions about what fish can’t do.

    The tuskfish cracking a cockle on a rock doesn’t prove that fish are as smart as chimps. It proves that the cognitive hierarchy we built—mammals on top, birds below them, everything else at the bottom—was a projection of our anatomy onto our definition of intelligence. An animal that solves the same problem a primate solves, in a medium 800 times denser than air, without hands or arms, using a body plan that hasn’t shared a common ancestor with primates in over 400 million years, isn’t failing to be smart. It’s being smart in a way we weren’t looking for.

    We cover fish cognition alongside dolphin communication, elephant memory, and primate social intelligence across our Animal Culture & Knowledge course—including why the most important discoveries in comparative cognition keep coming from the species we assumed had nothing to teach us.