Zoobiquity

  When cattle and horses that graze in the chaparral of the western United States lose their sense of direction, go weak in the legs, withdraw from other animals, or suddenly become violent, ranchers immediately suspect locoweed. Several varieties of this legume grow freely throughout the West; the numerous types can be identified by their blue, yellow, purple, or white blossoms that resemble small sweet peas. If the intoxicated livestock don’t die from walking off a cliff or blundering up to a predator, “locoed” animals can eventually starve or suffer severe, irreversible brain damage. Despite these dire consequences, some animals actually prefer the plant over their regular foraging options—and, tellingly, one taste of it makes them more likely to try it again. In addition to misadventure and death, locoweed produces another nasty problem that annoys ranchers. Like the cool-kid druggie in homeroom, one locoweed-eating animal can influence others to start. Handlers must be assiduous about removing locoed animals from the herd so the weed-seeking behavior doesn’t spread. And locoweed affects wild animals, too. Elk, deer, and antelope have been seen staring dully and pacing nervously after a few nibbles.

  A friendly cocker spaniel in Texas once sent her owners’ lives into a tailspin when she turned her attention to toad licking. Lady had been the perfect pet, until one day she got a taste of the hallucinogenic toxin on the skin of a cane toad. Soon she was obsessed with the back door, always begging to get out. She’d beeline to the pond in the backyard and sniff out the toads. Once she found them, she mouthed them so vigorously she sucked the pigment right out of their skin. According to her owners, after these amphibian benders Lady would be “disoriented and withdrawn, soporific and glassy-eyed.” Soon the neighbors’ dogs weren’t allowed to come over to play, for fear that they’d pick up Lady’s bad habit. Lady’s family dreaded the raised eyebrows when they hosted parties and PTA meetings and so started withdrawing from their social obligations because of the dog’s new inclination. As amusingly recounted in a story on National Public Radio, one night the dog’s human mistress found herself in the backyard at four in the morning, desperately searching for a toad to give to Lady—literally enabling the addiction so the dog would finally come inside and the family could get some sleep.†

  Giving alcohol to animals—or watching them imbibe on their own—has entertained humans for centuries. In colonial New England, hogs that got tipsy after eating pomace (the pulpy by-product of cider production) may have provided the sounds that gave rise to a term popular in the day: “hog-whimpering drunk.”

  Aristotle described Greek pigs becoming intoxicated when “they were filled with the husks of pressed grapes.” According to the author and alcohol historian Iain Gately, Aristotle also recorded a way to trap wild monkeys by enticing them with alcohol. The technique involved strategically laying out jugs of palm wine for the simians to sample and then simply plucking them up after they got drunk and passed out. Apparently the trick worked just as well in the nineteenth century: Darwin described the same procedure in The Descent of Man.‡

  You can see modern-day drunken monkeys in a BBC video shot on the Caribbean island of St. Kitts. The Curious George look-alikes, with their bright, rounded faces, dart among bikini-clad hotel guests. Like teens at a wedding, they wait until no one’s looking, then run off with half-drunk daiquiris and mai tais. What comes next is enhanced by the video’s quick-cut editing but mirrors what happens to other animals, too, from squirrels drunk on fermented pumpkins to goats sauced on spoiled plums. The monkeys weave. They stagger. They list. They tip over. They try to stand up. They pass out.§

  Of course, comparing drug use in animals and in humans has limitations. The superpotent, rapidly addicting, Ph.D.-designed forms of opioids, marijuana, and cocaine peddled to and used by today’s human addicts differ significantly from naturally found plant sources of these psychoactive agents. The alcohol available to human consumers is much more refined and intense than what Mother Nature can make on her own. Furthermore, for scientists it’s frustrating that most examples of wild animal substance use and its effects are based on observation and anecdote. Indeed, the few papers that do examine wild animal models of intoxication bemoan this fact and call for more stringent field studies. But controlled conditions do occur more frequently in the lab, and animal drug use and abuse have been widely studied in that setting.

  Rats, the most examined animal in substance abuse research, have revealed many crossover aspects of intoxication. Like us, in order to start using a substance, they first must overcome an initial aversion. They lose neuromuscular control when under the influence of certain drugs. They seek out and self-administer doses—sometimes to the point of death—of various drugs, from nicotine and caffeine to cocaine and heroin. Once addicted (researchers sometimes say “habituated”), they may forgo sex, food, and even water to get their drug of choice. Like us, they also use more when they’re stressed by pain, overcrowding, or subordinate social position. Some ignore their offspring. (Conversely, drug seeking can decrease in lactating female rats.) But rats, although they’ve become the most popular models for addiction in mammals, are not the only lab animals to be tempted by inebriating substances.

  Bees “dance” more vigorously when they’re dosed with cocaine. Immature zebrafish hang out on the side of the tank where they were once given morphine. Methamphetamine juices snail memory and performance the way Ritalin might boost a sophomore’s PSAT scores. Spiders on a range of drugs from marijuana to Benzedrine spin webs that are overly intricate or nonfunctional, depending on the drug.

  Alcohol can make male fruit flies hypersexual and pursue more same-sex matings, perhaps because the ethanol interferes with their reproductive signaling mechanisms. Even humble Caenorhabditis elegans, a tiny worm, moves more slowly when exposed to levels of alcohol similar to the ones that make mammals intoxicated. And the females lay fewer eggs when drunk.

  Drug seeking. Raised tolerance. Attempts to get stronger and more frequent doses. Begging or jonesing for a drug. If human beings were the only creatures who showed these classic addiction behaviors, then we could say the disease is uniquely human. But clearly we aren’t alone. Across the animal kingdom—not just in mammals with highly developed brains—animals react to drugs in comparable, although of course not totally identical, ways.

  That we can see parallel effects from intoxicants, whether the organism is a rodent, a reptile, a firefly, or a firefighter, strongly suggests two things. First, animal and human bodies and brains have evolved designated doorways for some of nature’s most potent drugs. Called receptors, these doorways are specialized channels on the outsides of cells that allow chemical molecules to enter. Receptors for opiates, for example, have been found in some of Earth’s oldest types of fish as well as in humans, and even in amphibians and insects. Receptors for cannabinoids (the intoxicant found in marijuana) have been identified in birds, amphibians, fish, and mammals as well as mussels, leeches, and sea urchins. This introduces the biological likelihood that opiates and cannabinoids—plus many more psychoactive substances—play key roles in maintaining the health and safety of animals. Indeed, these drug-response systems may have evolved and endured because they actually increase an animal’s survival chances, or “fitness.” More on that in a moment.

  These animal examples also challenge anyone who would stigmatize addicts or moralize about the disease. What you might see as a personal failing in your no-account uncle who ruins every Thanksgiving with his drunken antics is not a uniquely human impulse. Uncle Bill is not alone in the animal kingdom in seeking and responding to chemical rewards. Maybe knowing that won’t make the annual get-together any more pleasant—or his life any easier. But the fact remains that driving his addiction is a chemical reward system shared by other animals, from worms to primates, which has been in existence for millions of years. True, Uncle Bill can choose between a trip to the liquor store and a trip to his AA meeting. But if a fruit fly had the same option, it, too, might sometimes take a rain check on sour coffee in a Styrofoam c
up in favor of a warm, soothing hit of ethanol.

  Jaak Panksepp never expected to make his name by tickling rats. He’d planned to be an architect or an electrical engineer or, at one point, inspired by his University of Pittsburgh freshman classmate John Irving, a writer. But an internship at a mental hospital when he was an undergraduate set him on a different path. Seeing how the patients there required a wide range of treatments, from short-term stays to padded cells, made him want to understand, he says, “how the human mind, especially emotions, could become so imbalanced as to wreak seemingly endless havoc upon one’s ability to live a happy life.” And so he became a psychologist and, later, a neuroscientist. He now holds a position that gives him a unique vantage point on how the brains of many species work. As the Baily Endowed Chair of Animal Well-Being Science in Washington State University’s College of Veterinary Medicine, Panksepp brings his expertise in human emotional systems to a department devoted to the health of nonhuman animals.

  Panksepp specializes in what goes on chemically and electrically in the brains of mammals when they play, mate, and fight, or separate and reconnect. And he is convinced that human addictive behaviors stem from ancient parts of our brains that are shared across species.

  Rat tickling came in the mid-1990s, after Panksepp had spent several decades studying play urges in rodents. Using an audio device that measured the ultrasonic vocalizations of bats, Panksepp had discovered that rats make two very different sounds when they’re playing. Happily engaged rats emit abundant high-pitched chirps at about fifty kilohertz—much higher than we can hear with the naked ear. To Panksepp it sounded happy, a bit like childhood giggling and laughter. He wondered if the animals would make this sound under other circumstances. One morning, he took a rat accustomed to being held by humans, gently rolled it onto its back, and tickled its belly and armpits. Instantly he heard it: fifty kilohertz vocalizing. He tried another rat. Same thing. Rat after rat, eventually over many years and in many different labs, vocalized at fifty kilohertz when they were tickled in this way.

  Panksepp and others found that rats make this “happy” sound in several other specific situations. When they’re copulating. When they’re about to get food. When a lactating mother is reunited with her offspring. But most especially when two friendly rats are playing with each other.

  Their other major vocalization registers at a much lower—but still inaudible to human ears—twenty-two kilohertz. Rats make this very different sound when they’re alarmed, anticipating a scary situation, when they’re fighting, and especially when they’ve been defeated in a skirmish. Although not a measure of physical pain, it apparently does reflect psychological distress or psychic pain. Baby rats make a version of it when they’re abandoned by or isolated from the warmth of their mothers.

  Panksepp says that when you run these sounds through a machine that translates them to a frequency we can hear, the high-pitched notes are roughly analogous to human laughter. The low-pitched calls sound like human moaning. He’s found rats make the higher, chirping sound when they’re anticipating receiving drugs they desire. They utter the lower, moaning sound when deprived of the drugs and experiencing withdrawal.

  Panksepp thinks it’s no accident that rats emit the same sound when they’re in psychic pain and when they’re denied a drug they crave. “Pain” is a word that came up again and again in my interviews with human addicts and the doctors who treat them. Overwhelmingly, addicts report that they need their substances to “dull the pain,” “make the pain go away,” or “make the suffering disappear.”

  Rarely do they mean literal, physical pain (although many addictions, especially to opioids, begin with a prescription for relief of bodily pain). The pain that addicts describe is more of an ineffable internal ache—an emotional throbbing or social tenderness.

  Panksepp is not the first to wonder whether other animals experience life in a way that could be called “emotionally” painful. This fundamental question has puzzled thinkers for generations: Do animals feel things the way we do?

  Charles Darwin tackled the issue in his 1872 book The Expression of the Emotions in Man and Animals. Trying to extend his principles of evolution beyond anatomy, he argued that natural selection could be applied to emotion and behavior. The idea didn’t catch on. Darwin was up against two centuries of René Descartes’s insistence on a dichotomy between body and soul. For Cartesians, only humans—specifically, men—possessed a soul, which was also the seat of intelligence. Having neither soul nor emotions, animals existed in a purely physical realm. Instead of “I think, therefore I am,” Cartesians believed that for animals it was more like “I can’t think, therefore I can’t feel.”

  Without the tools to track—or even define—emotions in nonhuman species, the behaviorists of the early twentieth century, like J. B. Watson and B. F. Skinner, were obliged to infer what an animal might be experiencing solely by observing its behavior. Here the differences between animals and humans really did get in the way. The facial muscles of most animals don’t react in ways that clearly communicate pain to a human observer. Most animals don’t vocalize when they’re hurt (at least not at frequencies we can hear)—possibly as a self-protective strategy against attracting predators. Many withdraw instead of seeking help. So different are these responses that they supported the behaviorists’ idea that animals don’t, or can’t, perceive physical pain.

  Because they couldn’t see what was going on inside the cranium, the behaviorists concluded that animal conduct occurred without awareness. If a creature didn’t “know” it was in pain, then it couldn’t possibly feel pain. Only human brains (and perhaps some other highly developed simian brains), they believed, functioned at a level of cognition high enough to process the unpleasant sensations of pain. Although the behaviorists were trying to reconcile body and mind, they succeeded only in further splitting them. Animals went from being soulless physical entities to boring biological machines. Remarkably, the notion that human consciousness was a prerequisite for feeling pain persisted into the last part of the twentieth century.‖

  And in some cases tragically, this belief was applied to another group of beings who can’t use words to describe their experiences: human infants. The conventional medical wisdom until the mid-1980s held that newborns’ neurological networks were immature and thus subfunctional. The prevailing doctrine was that babies “couldn’t feel” pain the way older humans do.a

  Although this view persisted for an uncomfortably long time, pain management is now a priority in both veterinary medicine and human medicine—including, thank goodness, pediatrics.

  Advanced brain imaging and other technologies are emerging that allow us to directly study the brain’s emotional systems. The techniques are providing evidence for Darwin’s view that emotions, like physical structures, have evolved. They are subject to natural selection based on their fitness benefit to individuals. And the reason is pretty simple. What we call “feelings” or “emotions” are not airy, intangible thought-vapors that emanate, auralike, from our brains. Emotions have a biological basis. They arise from the interplay of nerves and chemicals in the brain. And like other biological traits, they can be retained or rejected by natural selection.

  Of course, how an animal experiences the world cannot be fully known to a human being. Some scientists, including Joseph LeDoux, an author and neuroscientist at New York University, object to using the word “emotion” when describing the interior world of animals. LeDoux coined the term “survival circuits” to describe the hardwired brain systems that drive animals to defend themselves and promote their well-being.

  Randolph Nesse, a University of Michigan psychiatrist and a leader of the growing field of evolutionary medicine, put it this way in a paper in Science: “Emotions … shaped by natural selection … adjust physiological and behavioral responses to take advantage of opportunities and to cope with threats that have recurred over the course of evolution.… Emotions influence behavior and, ultimately, fitness.”
Nesse’s view echoes that of E. O. Wilson, who wrote, controversially at the time, “Love joins hate; aggression, fear; expansiveness, withdrawal … in blends designed not to promote the happiness of the individual but to favor the maximum transmission of the controlling genes.”

  Whether or not we use the word “emotion” to describe it, animals seem to be rewarded with pleasurable, positive sensations for important life-sustaining undertakings. These are activities such as finding food, approaching mates, escaping to a hideout, outrunning a predator, and interacting with its kin and peers. The joyful pleasure a young human or animal feels upon reuniting with a caretaking parent encourages bonding, for example. Pleasure rewards behaviors that help us survive.

  Conversely, depression, fear, grief, and isolation, among other negative sensations, indicate to an animal that it’s in a survival-threatening situation. Anxiety makes us careful. Fear keeps us out of harm’s way. Imagine the trouble you’d be in if you didn’t feel anxious and fearful when encountering a rattlesnake on a hiking trail or a masked gunman at an ATM.

  And there is one thing that creates, controls, and shapes these extremely important feelings: tiny hits of addictive chemicals stashed in microscopic pouches (called vesicles) in our brains.

  It’s as though we’re all born with an internal Pyxis 3500 machine that opens specific drawers in response to our unique genetic “thumbprints” and behavioral “codes.” Our personal chemical-dispensing apparatus is stocked with tiny capsules of natural narcotics: time-melting opioids, reality-revving dopamine, boundary-softening oxytocin, appetite-enhancing cannabinoids, and many more—some of which haven’t even yet been identified.