Think about your most recent meal. Try to remember how much of it you prepared yourself. Did you choose, sample, forage, pay for, hunt, kill, pick, or pluck the ingredients? How much processing did you do? Did you cut, grate, shell, chop, peel, or gnaw? Did your food satisfy your hunger? Did it nourish you?
For something that must happen consistently—or else you die—eating on planet Earth is surprisingly hard to do for animals. A lot of skill must go into hunting adeptly, and the same is true for non-carnivorous forms of food gathering, like grazing and foraging. Another challenge about eating is that it’s costly—it takes energy and time. If you’re a wild animal, you have to wonder if a predator will attack you while you’re searching for your own meal. If you’re a predator, you have to know the Predator’s Sequence and hope it goes well each time you hunt.
Being able to procure your own food is one of the most important markers of animal adulthood, perhaps even a stronger sign of full maturity than departing a home range, having offspring, or developing the physical characteristics of adulthood, such as horns, antlers, manes, or deep voices. Just as animals need to learn how to avoid predators, make friends, and communicate sexual desire and consent, they’re not born knowing how to find food perfectly in the wild. Starvation is a major risk adolescent animals face—often bigger even than predation.
Dispersing animals are hungry, because learning to feed themselves is hard. And not all animals do it willingly—or well. The world is full of adolescents and young adults newly out on their own who haven’t yet learned the necessary skills to find their own food. Hunger and the fear of starvation are so deeply ingrained in us, they even haunt protagonists of coming-of-age literature.
Katniss Everdeen, the eighteen-year-old main character of Suzanne Collins’s aptly named Hunger Games series, survives in large part because she is able to hunt her own food. The archery and foraging skills she learned from her father keep her and her starving family alive at the beginning of the story. Later, they’re keys to her survival in the arena. At one point, when she can’t find food, Katniss digs through a garbage bin and agonizes over whether to steal a loaf of bread.
Katniss’s desperation in that moment recalls that of the also-eighteen Jane Eyre, who, like a “lost and starving dog,” begs for food at a bakery, shamefully offers to trade her leather gloves for a morsel, and finally eats porridge from a pig trough. Luckily for the starving Eyre, a farmer finally gives her a slice of bread. That smidgeon of food sustains Jane until she reaches the home of her long-lost relatives, ensuring her survival.
Frankenstein’s creature—as poignant a coming-of-age disperser as any in literature—fares less well in his attempt to charm an old man in a hut and some alpine villagers into sparing him a bite to scrounge. He is chased away and threatened with weapons and finally has to eat berries in the forest and hide in a hovel, stealing food from cottagers in order to stay alive.
For modern, affluent young adults heading into nonfictional worlds on their own for the first time, dying of starvation is no longer a central concern. But this is definitely not the case for everyone. According to the Urban Institute, a Washington, DC–based nonprofit research organization, nearly seven million young people between the ages of ten and seventeen face food insecurity on a daily basis in the United States.
Individuals who lack resources have less choice in what they eat and how they obtain it. This is a serious, overlooked fact when it comes to understanding adolescent behavior. Across all human societies and across all species, hungry individuals are forced to take greater risks. Starvation is not the only way hunger can be deadly.
Hungry adolescent animals run into exposed open meadows or hunt under a full moon even though it makes them more visible. They edge out onto thin branches and into rushing water, forced to take the most dangerous, least desirable routes because of their lower status and lack of experience. They’re also forced to eat poor-quality food—less nutritious and less tasty. By contrast, dominant and older animals can wait in safer positions. They eat choicer food and more of it. Less driven by the feeling of hunger, with its underlying fear of starvation, sated animals are also safer ones.
Hunger impels already vulnerable human adolescents to take risks. The Urban Institute reported that food-insecure teenagers in America steal, sell drugs, and may become involved in sexual transactions simply in order to eat. In addition to short-term physical risks, these food-seeking strategies may result in incarceration or criminal records, which further compromise their future opportunities.
For Slavc, even with the hunting practice he’d had with his parents back in the Slovenian forest, finding food was a challenge. Growing hungrier with each passing day, Slavc would have gotten more and more desperate. His hunger would have pushed him to take risks he wouldn’t otherwise consider.
PACKING UP
Humans prepare for dispersal and its dangers, including starvation, in many ways. They save money; they pack food; they stockpile information; they gather the supplies they’ll need. Young wildlife don’t make such complex arrangements. Nonetheless, animals may get a biologic assist from deep within their own bodies, one that human adolescents likely share.
One of the first things many parents notice when their kids move out of the house is that the grocery bill goes way down. Yes, it’s because there’s one fewer hungry person in the house, a hungry person whose growing body needed a lot of fuel. But teenagers’ legendarily insatiable appetites may have another cause, one with its roots in ancient pre-dispersal biology.
Research shows that just before some young animals get ready to leave the nest, some of their genes are activated (or “upregulated”), causing their bodies to change in ways that prepare them for life in unknown and possibly dangerous worlds. The outside environment cues the genes, which in turn direct body growth, a two-way relationship called genetic/environmental interaction.
Before migration, many mammals begin to store fat (unconsciously, of course), which helps if food is scarce on the road ahead. A young adult marmot, heading into a dangerous world without her parents, benefits from a fat-grabbing metabolism that packs extra energy supplies right onto her body. With this genetic assist, she may be a little less likely to die of starvation. Marmots and other dispersing animals may be further protected by another body system that revs up in adolescents: the immune system. Activated immunity will help them fight off the new pathogens and infections they’ll encounter on their expeditions away from home.
Shifts in appetite and resistance, occurring silently and unseen deep within the bodies of animals on the brink of leaving home, have useful parallels for humans. Researchers are only beginning to hypothesize how these findings might be applicable to our own species. Perhaps ancient animal dispersal physiology encourages the body to hoard calories against starvation, thus playing a role in the obesity rates of teens and young adults. Or take the timing of autoimmune disorders like lupus, multiple sclerosis, and ulcerative colitis. They often come on in adolescence and young adulthood. Perhaps the life cycles of these diseases can be understood by considering the immune system overhaul seen in adolescents prior to dispersal.
With changes in their DNA preparing their bodies for an uncertain journey ahead, ravenous hunger becomes a central preoccupation for dispersing young animals. The lucky ones have informed parents who teach them tricks of independent living and support them while they get the hang of it even after they leave home. Animals with no parental backing have to figure it all out on their own.
A week into his journey, near the Ljubljana airport, Slavc finally found a meal. He killed and ate two red foxes. His choice of prey shows some desperation. Wolves prefer to eat deer, but taking down a deer is a difficult feat. And so it’s common for young adult predators in the early stages of independence to eat food that’s easier to catch.
According to wolf expert David Mech, North Carolina red wolves eat a range of game, from white-tailed deer, raccoons, and marsh rabbits to rodents. But what is interesting is who eats what. In one study, adolescents consumed mostly rats and mice, while adults feasted on deer. Raccoons and rabbits went to the younger adult wolves with developing experience, who were building the stamina and smarts to take down deer. By the time they were adults, the wolves almost never had to eat a rodent. Like lower-paid, entry-level employees working their way into better salary ranges, young wolves saw their food quality improve as they gained expertise.
Being able to hunt a deer is also the standard used by the Endangered Wolf Center, a wildlife sanctuary we visited outside St. Louis. The oldest wolf sanctuary in the United States, the EWC takes in orphaned pups, trains them in life skills, and then releases them back into the wild. While they’re being trained, the younger wolves mostly go after raccoons, possums, and rodents that wander into their enclosures. But the rehabbers are carefully watching for those skills to get good enough to take down big prey, like a mule deer. They will supplement a wolf’s feedings until they’ve witnessed him or her kill a deer. Ideally, they like to see more than one confirmed kill before deciding a wolf is ready to go back to the wild.
Ben Kilham, a black bear conservationist and wildlife consultant in New Hampshire, takes a similar approach to the orphaned bear cubs he rescues, rehabilitates, and releases back to the wild. “I don’t exactly teach them how to find food on their own,” he says. “But I keep them protected while they learn how to do it.”
As we’ve seen, finding food isn’t easy in nature. Inexperienced meerkats often fumble with and even lose a precious scorpion before they can consume it. Even the most iconic hunters on the planet have to make many attempts before they have a successful kill. On average, lions hunting on the Serengeti and wolves in North America have an 80 percent failure rate—chasing and attacking five different animals for every one they take down. For Indian tigers and Arctic polar bears, a 90 percent failure rate is the norm. The availability of prey in the landscape plays a major role in hunting success. But so does the experience of the hunter.
Ursula would have spent months learning how to fish; for king penguins, learning to hold their breath long enough underwater is a big step. Similarly, dispersing humans with little food know-how typically fill themselves up with cheap, easy-to-obtain, lower-quality items, aka junk food, until they have the skills and resources to do the human equivalent of taking down a deer: paying for and/or preparing a meal.
There’s another fascinating reason adolescents and young adults may be attracted to foods their elders reject. Changes in sensory perception during wildhood can make animals literally see food differently. Capuchin monkeys, for example, are suddenly able to see a wider range of colors as adolescents than they can as babies and adults. The colors fade out as they age. Biologists think this may make them better at seeing certain fruits, giving the younger monkeys a head start when they have to start competing with adults for foraging patches.
Sockeye salmon, when they’re juveniles and adults, can see in the ultraviolet range. But for a brief period of time when they’re adolescents, they suddenly lose that ability. It may have something to do with avoiding a certain kind of prey, because much of what sockeyes eat is marked with ultraviolet designs. Biologists postulate that temporary blindness to this food “packaging” somehow gives these fish a survival advantage they need during wildhood.
Adolescents may actually see, smell, and taste differently to protect them from foods that might harm and attract them to foods that might benefit them during this period, like food cravings and aversions during pregnancy may support survival of the growing fetus. Adolescents eat poorly, because they’re lowest-status, last in line, and have to forage in the most dangerous areas with the poorest range of choices and the least-nutritious options. As we’ll see, the oddities of adolescent appetites also help dispersing young animals adjust to novelty as they learn what and how to eat in their new food landscapes.
THE ADVERSITY ADVANTAGE: THE SQUIRREL WHO HAD GRIT
Among applied animal behaviorists (those who use their expertise directly to train or motivate animals), it’s common knowledge that not all food is created equal. They know that dogs will find a bit of cheese, a chunk of liver, or a dab of peanut butter much more exciting than a mundane piece of kibble. Applied behaviorists call these special morsels “high-value treats,” and use them strategically to encourage animals that may be distracted or struggling to learn a new skill. High-value treats are out-of-the-ordinary and desirable, and they both elicit and reward motivation. Wild versions of high-value food can be found in nature too. For the northwestern crows of coastal British Columbia Japanese littleneck clams are that treat.
In terms of crow time and energy, feasting on these clams is very expensive. The mollusks are difficult to source and preparing to eat them is time-consuming. First the birds have to locate mudflats where the clams are likely to be. Then they have to dig them out of the sticky ooze with their beaks. Lugging the heavy shells, they fly high into the air and drop the clams on the nearby rocks to break them open. If the shell doesn’t crack, they have to retrieve it, fly it up in the air again, and re-drop it. Some shells need four or five flights to finally open. That’s a lot of time and energy per clam.
When two Simon Fraser University scientists decided to take a closer look at the crows’ seemingly inefficient behavior, they noticed something strange: an extra step in the process. The crows spent a great deal of time finding the clam, digging it out of the mud, and lifting it off the ground. But then sometimes, a crow would drop the shell and leave it behind, without taking it up into the air and dropping it on the rocks. Why would the crows go to the trouble of digging up perfectly good clams only to abandon them halfway through the process?
It turned out that the rejected clams were too small. By hefting the clam after dragging it out of the mud, experienced crows could calculate the potential energy content of the meat against the output they would have to spend on the flying-dropping cycle to extract it.
And who was better at making that calculation? Older, more experienced crows. Inexperienced crows invested more in the process of locating, digging, hefting, calculating, flying, dropping, and eating. And even once they had done all that, they had to outwit the scrounger crows—freeloading birds that don’t bother with the whole exhausting extracting ritual and simply lurk near the action to sweep in and steal the hard-won gains of other crows. With scroungers too, the younger and less experienced were at a disadvantage. Their meals got stolen more often than those of older birds. But the crows got better the longer they stuck with it.
Some of the birds may have had a special attribute fueling their success: persistence, stick-to-itiveness, tenacity—the special combination of passion and perseverance that the psychologist Angela Duckworth calls “grit.” Grit is a lot of things, part temperament, part biology, part training, and part environment, with expectation and opportunity thrown in. According to Duckworth, for humans, achieving one’s goals requires sustained effort, practice, and high motivation.
Shrink the hyena from Ngorongoro Crater would probably have measured very high on a grit scale. From hyenas to tropical blackbirds to meerkats, individual differences in levels of persistence have been studied in animals. To measure it, scientists use food, often hidden in a puzzle that forces the animal to put effort into getting it. Confronted with the same obstacles, some animals give up more readily than others.
Some hyenas continue struggling to extract raw meat from a puzzle box while others give up after a few tries. Similarly, some meerkats keep trying to extract a crunchy scorpion from a jar long after their peers have given up.
Just as it does for people, grit improves outcomes for animals. Persistent animals displaying sustained effort, repeated attempts (practice), and high motivation are the most likely to solve problems and innovate. Time spent working on a problem correlates with success, whether it’s the meerkat who finally succeeds in prying the scorpion out of the jar or the hyena who finally figures out how to extract the meat from the puzzle box. Sustained effort improves an adolescent’s ability to face every challenge of wildhood. Staying safe, building social skills, communicating sexuality, and ultimately survival itself are all improved by repeated attempts during wildhood.
Animal grit contains lessons for our species: necessity may be the mother of persistence. It turned out that the most persistent animals were not the dominant, mature adults. They were younger and subordinate. As we know, subordinates have something else that may dial up their heightened stick-to-it-iveness: hunger. They have fewer resources. To get what they need to survive, adolescents and young adults must be tenacious, sticking around longer after older, dominant animals—better fed and therefore perhaps less motivated—have given up.
Animal studies add another notable observation that Duckworth similarly champions in humans: grit isn’t a fixed trait. It can be developed. Squirrels who kept at the challenging task of extracting a treat from a specially rigged container became more persistent—and more successful—the more they tried. Motivated by a hazelnut, the squirrels kept at it. And in not giving up, their persistence increased. In other words, grit grew more grit.
INFORMED MOTHERS
When white-tailed ptarmigan mother hens want their chicks to eat a healthy meal, they use special peeps to point out plants with higher protein loads. The lucky chicks whose mothers are better nutrition “guides” continue to seek out more nutrient-rich plants even when they grow older and Mom is no longer around to remind them. When lambs graze with their ewe mothers and calves graze with cows, the young eat a wider variety of more nutritious foods.
Young humans with nutritionally knowledgeable parents are also lucky. Studies of parental influence on eating behavior show that parents are strong nutrition influencers, with a time-sensitive window of opportunity, during young childhood, to shape enduring food preferences and habits. Human parents transmit information about food to their adolescent offspring in a number of ways, by cooking with them, teaching them to market or read labels, and passing down techniques for making, storing, or preparing food.
But learning what to eat is quite different from knowing how to hunt, forage, find, or steal your own food. With animals, wildhood is when food-handling skills are imparted by parents and the larger community. It begins as soon as the young animal’s strength and focus are strong enough.
Orcas use a technique called “stranding” to surf up onto a beach, grab a seal or penguin, and then slide back into the water. Adult whales teach their offspring this behavior by pushing them up on shore with an incoming wave, directing them to a prey item, and then intervening if they get in trouble surfing back out with the wave. It’s a really dangerous move; if they don’t learn how to do it exactly right, they risk getting stranded for real. After learning it from their parents, adolescent whales will sometimes practice this behavior with their peers, without parents around, riskily play-stranding with friends.
For human parents, transmitting food safety knowledge to their children is not nearly as dramatic. Today in our species it generally comes in the form of information about foods that may cause illness and even death in the short term (poison, allergy, anaphylaxis) or long run (diabetes, heart disease, cancer). While the specifics are quite different, the parental intention—to help offspring eat well and stay safe—is the same.
Young animals living in cooperative groups who hunt and forage must learn to participate in and contribute to collective efforts. Again, mothers appear to play an important role. Humpback whales like Salt catch fish using an ingenious system called “bubble net feeding.” Working as a group, four or five whales swim around a shoal of fish, creating a kind of water tornado that traps the fish in its vortex. The whales blow bubbles into the spiral, which confuses and blinds the fish, preventing them from escaping. Once the shoal is all rounded up, the whales can swoop in from below, their giant mouths open, and slurp down an easy cone of seafood. This behavior must be learned and practiced, and there’s evidence that it’s passed from mother to calf and within groups.
In the 1980s, in the Gulf of Maine, around the time Salt was pregnant with her first calf, humpback whales were inventing a new and improved flourish on the bubble net technique. Called “lobtail feeding,” it involved an extra tail smack on the surface of the water before the bubble-blowing commenced. The start of this new behavior coincided with the whales’ shift to a different kind of fish that has a tendency to jump out of the water when it’s scared. The tail smacks likely created a sound-wave “lid” for the top of the bubble net, keeping the fish where the humpbacks wanted them. It’s pleasing to think that one of the many skills Salt may have taught her fourteen offspring when they were adolescents was how to spin a bubble net and how to deploy the lobtail method. Whether she did or not isn’t known, but her fellow humpbacks in the Gulf of Maine certainly did, and these informed mothers were likely teaching the behavior to their lucky calves and their peers.
HUNGER GAMES
Hunting other animals is hard to do. Making the Predator’s Sequence look easy can take years of practice. Some animal predator parents create opportunities for their young to rehearse before needing to perform this life-sustaining dance by themselves. This often involves bringing live prey to them.
Mother leopard seals present their pups with wounded penguins and encourage them to practice the kill. Cheetah mothers bring their kittens injured gazelles. Similarly, puma mothers provide fawns, beaver pups, skunks, and porcupines for predatory “edu-tainment.”
Carnivorous meerkats send their young to scorpion school. There, the offspring learn to safely kill and consume the venomous thick-tailed Parabuthus scorpion. Experienced adults remove the stingers from these arachnids before presenting them, still alive, to the young meerkats. Gradually, as the maturing meerkat becomes more scorpion-savvy, adults bring a live specimen—stinger and all—and supervise while the offspring disable, disarm, kill, and consume it.
Predator training is part of the dispersal process for Spanish imperial eagles as well. In fact, it’s what kicks off the separation process that ends with stooping runs and parental meanness. Like other birds of prey, these Spanish eagles follow a reliable pattern in how they taper off feeding their emerging young adult birds.
At first, the parents (both Mom and Dad) find their young wherever they happen to be perched and bring food to them. The parents alight next to the young bird, tear off a piece of meat, and offer it beak-to-beak—just like they used to when the chicks were nestlings. But after a few days, that babyish kind of feeding starts to decrease. The adults still bring rabbits or rodents for their son or daughter, but instead of cutting up the meat and feeding it to them, the adults land at a distance. If the youngster wants to eat, he or she has to fly to get it. And once the youngster arrives, the parent stays there, but doesn’t help feed it. The youngster has to figure out how to tear off its own meat while the parent watches.
That phase transitions to a third stage, in which the young bird must fly to the parent who has the food, but now the parent flies away immediately and the youngster feeds all alone. As the parents feed them less and less, the young start to get more and more stressed. And they don’t suffer this change in food supply and schedule quietly. They all beg—but their parents ignore their cries (the start of parental meanness). Standing firm, they bring food less and less frequently until their kids finally leave for good.
What makes this eagle process even more interesting—and high-stakes—is that the eagle parents do it before the offspring even know how to hunt. The young eagles aren’t competent, because they haven’t done it before. That seems illogical. How are they supposed to know how to listen for a mouse or grab a rabbit? How to swoop and stoop and seize and rip? Or, said another way, to detect, assess, attack, and kill?
The Spanish researchers postulated that parental meanness combined with “indifference” to begging forced eagle offspring to practice a skill vital to success as an eagle hunter: flying. The parents seemed to be using their offsprings’ hunger to motivate them to learn the skills that would keep them alive as independent adults.
Whether it’s bubble-net feeding, scorpion school, or beach stranding lessons, adolescent animals rely on their elders for crucial knowledge about what and how to eat. The ability to feed oneself translates into better survival. Self-reliance of this kind—and the confidence that comes with it—also prepares human and other animals to begin taking care of others, whether offspring, kin, or members of the community.
THE SELFISHNESS OF SACRIFICE
Animal parents pour time and energy into making sure their offspring learn the skills they need to survive in the world. Sometimes animals invest more in offspring who look like they are going to make it into adulthood. A study of leopards found that as their offspring got older, nearing independence, the mother cats actually increased the amount of time they spent finding prey for their adolescent cubs to practice on. In fact, these mothers put more time into doing that than they did into getting food for themselves. In human terms, that’s not unlike a parent taking an extra job or two to fund the education of a promising son or daughter.
But life as an animal parent-teacher is not all altruism and encouraging growls and purrs. Learning from parents has limitations, and as a parent, having your own offspring as students can be taxing. A young wolf or orca can mess up the group hunt; cluelessness and adolescent antics can cost the family a meal. Animal parents may tire of teaching naive young to hunt and forage, especially as the offspring get older and their puppy license nears expiration.
These parent-child teaching conflicts are bypassed by some species in which the mentoring of young animals is done by a non-parent adult from the community. When banded mongooses in Uganda are about one month old, they leave the den and choose a foraging advisor to guide them in the intricacies of gathering food from their preferred diet. These non-related adults show their mentees how to steal reptile eggs, hunt snakes and birds, and scavenge for fallen fruit. The adolescent mongooses become territorial over their mentors and won’t let other peers near them. A few months later, when the mongooses have learned what they need to learn, the escort relationship ends. But those young adults will forever prefer the foraging areas and techniques their mentors taught them over the ones their own parents use.
I’LL HAVE WHAT SHE’S HAVING
Adolescent animals, with their less-than-stellar hunting and foraging skills, and their suboptimal diets, are culinarily vulnerable in another way. They often copy their friends’ food choices.
For example, if young Norway rats are given a choice between a tasty food they prefer and an unpleasant food they don’t, they’ll choose the tasty one every time. But in one study, when rats reached puberty and were placed with peers, their food choices shifted. They became twice as likely to defy their own taste preferences and copy those of their peers. To test whether this peer pressure went beyond taste preference, researchers offered sodium-deficient rats food containing health-improving amounts of salt. Once again, the adolescent rats rejected the fortified, healthy-for-them food in favor of whatever their peers were having. Remarkably, adopting peers’ food preferences extended to poison: despite having been sickened by tainted food in the past, when a rat saw peers eating it, that rodent ate the toxic food too.
Rats carry scent clues on their fur and whiskers that reveal to their friends what they’ve been eating. But an even stronger influence is the smell of food on peers’ breath. Even when it’s bitter (a taste rats don’t like), as long as they smell their friends’ breath on the food, adolescent rats want to eat it. Similarly, they will follow along and develop aversions to the same foods their peers avoid.
To a human parent, the influence of peer pressure on adolescent food choice may be frustrating, especially if it comes after nearly a decade and a half of careful food education. Or food issues can seem like a warning sign of adolescent rebellion. Throwing away a healthy lunch, refusing to participate in a family dinner—these common adolescent behaviors can upset parents and hurt their feelings. But there is an ecological reason that explains the behavior in rodents and may influence humans as well. Peer information about a local environment is often more up-to-date than parental information. Set in their ways, benefiting from resources, status, or tradition, older animal parents can be out of touch with changes in nutritional ecosystems that younger animals are much closer to—and much more affected by.
Peers not only offer up-to-date information, but during dispersal they can also be a valuable, sometimes lifesaving, support system. When male fossas, the lemur-eating carnivores native to Madagascar, transition into adulthood, they often team up with another male—either a brother or a peer-friend.
“By pairing up, male fossas can cooperate in their hunts, which might allow them to eat more and grow bigger than solitary fossas,” explains fossa expert Mia-Lana Lührs. Finding a compatible companion may be easier for two brothers, and the benefits of pairing up go far beyond hunting help. Finding another fossa he can tolerate enough to turn into a hunting partner eases a fossa’s future. If he doesn’t, says Lührs, that fossa will “find himself on the path to becoming a loner.”
Hanging with friends at the burger place or coffee shop eating waffle fries and drinking sweetened milk tea may not lead to the healthiest diet. But a parent concerned about their adolescent’s eating may be able to look at this behavior differently knowing that their kids are sharing the wildhood instinct to indulge in—and enjoy—food with friends.
A final point: as long as the eating isn’t terribly out of control, the most important part of the picture is not really the food, but rather those friends. In all social species, individuals define themselves within groups—independence comes from self-reliance, not isolation.