Zoobiquity (30 page)

We have one obvious thing in common with other animals and our own animal ancestors: we all have to eat. And echoes of the eating strategies of our animal forebears—
guided by fear, anxiety, and stress
—may remain with us, even today, in ancient, inherited eating neurocircuitry and behaviors. It means there may be a “disordered” animal eater lurking in every one of us.

My daily meetings with Amber took place in various locations inside the treatment unit or somewhere on UCLA’s campus: on a bench, under a tree. We delved into her childhood memories (such as they were; she was just fourteen, after all); her thoughts; and her visualizations of the future—all to get to the psychodynamic core of why she was afraid to eat.

Ecologists who study animals are, for obvious reasons, unable to engage in such dialogue. Like psychotherapists, they would never strive to understand a single animal’s eating behavior in isolation from the world around it. In fact, scientists who study animal eating know that a lot of an animal’s behavior around food depends on factors completely out of its control. Weather, food supply, position in the pecking order, and social hierarchy—all these can mean the difference between a belly that’s full and one that’s empty. And in the wild, one of the biggest diet determiners is the presence of predators. Biologists call it “the ecology of fear.”

To study this idea,
scientists at Yale built mesh-and-fiberglass field cages over areas of a meadow containing wild grasshoppers and their primary food source, naturally growing vegetation. In some enclosures, the grasshoppers were left to eat in peace. Those insects mostly munched on protein-rich grasses. But another group of grasshoppers was enclosed with an unpleasant surprise: predatory spiders. To protect the grasshoppers, the spiders had had their mouthparts glued shut.

The presence of the arachnids had a significant and surprising effect. Forced to share space with their mortal enemies, the grasshoppers all but gave up eating grass. But they didn’t stop consuming food altogether. They chose instead to eat goldenrod, a sugary, carbohydrate-laden flowering plant, instead. The same preference for sugar over protein was seen when the experiment was repeated and the grasshoppers’ choice was between a high-sugar cookie and a protein-rich bar. This means something very interesting, says Dror Hawlena, the ecologist who devised the experiment.
When stressed out by the spiders, the grasshoppers binged on sugar and carbs.

The threat of predation speeds up the metabolism of a variety of species, preparing them to react to the danger. Revving the engine burns fuel in the blood and muscles. To keep the engine accelerating, they need quick fuel. Simple sugars and carbohydrates fit the bill. Their chemical bonds come apart more readily than the long-chain fatty acids of leafy greens or the complex molecules of proteins, so they don’t require a lot of processing in the gut. The body can utilize their energy quickly.
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Psychiatrists studying eating disorders note that bulimic binge eaters rarely overconsume protein or leafy greens. Like the grasshopper, they focus their eating sprees—sometimes with obsessive intensity—on sugars and simple carbohydrates. (Stress eaters who don’t later compensate by vomiting or using laxatives sometimes kick this specific sugar-and-carb focus.)

In the Yale study, the insects’ food choices were driven by external factors beyond their control, in other words, the ecology of fear. In the presence of a predatory threat, they chose foods that would accelerate a lifesaving escape. These animals provide an underexplored possible context for a human binge eater’s food choices. They suggest an evolutionary origin. A stressed person’s decision to forgo the chicken breast and vegetables in his lunch box and consume candy bars instead can seem pointless, weak, and even self-destructive. But knowing that some nonhuman animals prefer high-sugar foods when they’re fearful could help a human stress eater better understand his own candy binge. While he knows it’s unhealthy for his waistline, blood sugar, and molars, the impossible-to-resist impulse may spring from a hardwired response to threats that for eons has saved animals’ lives.

Of course, a college undergraduate shoveling candy into her mouth late at night during finals week or an executive loading up on a sleeve of cookies before a business trip are separated from the grasshopper by genetics, brains, cultures, and, certainly, self-awareness. But as animals, they may share physiologic strategies for coping with stress, one of which could be an attraction to getaway-fueling simple sugars during times of stress.

And the ecology of fear influences not only
what
an animal chooses to eat. It also determines
when
. Light-dark cycles affect animals’ sense of safety. In some animals light may inhibit eating; in others it may enhance it.
In a study of gerbils, for example, researchers found that when nights were dark, the rodents ate substantially more. On bright nights illuminated by a full moon, making them more visible to predators, they ate less.
Another study, on rodents known as Darwin’s leaf-eared mice, found that shining a light on their cages was enough to make the mice cut their foraging time in half. They ate nearly 15 percent less than usual and, consequently, lost weight.
Scorpions have shown a similar aversion to bright nights. The bigger the moon, the less they foraged.
It’s known that
light therapy can reduce food cravings and overeating in some human bulimics. Animal examples could provide a context for these effects. Perhaps this is the evolutionary basis underlying the folk wisdom that a late-night urge to raid the refrigerator can be squelched by flooding the kitchen with bright light.

The ecology of fear can change an animal’s entire approach to feeding—even beyond what and when it eats. In his book about mountain lions,
The Beast in the Garden
, the science journalist David Baron tells an interesting story. Starting around the mid-twentieth century, mule deer around Boulder, Colorado, began behaving oddly. Instead of cautiously venturing out of hiding to feed at dawn and dusk as they used to do, the deer began eating, lounging, and even giving birth in full daylight on the lush, landscaped lawns of Boulder’s neighborhoods. This lackadaisical behavior coincided with unusually low numbers of predators in the surrounding region—wolves had been hunted to near extinction in the century before, and the mountain lion populations had been decimated. Baron notes that “
with its large carnivores gone, Boulder’s herbivores flourished.”

Around the same time, something similar was happening in Yellowstone.
For fifty years, the landscape had been completely devoid of a fearsome predator: wolves. This had an intriguing and measurable effect on Yellowstone’s elk. They relaxed. They began grazing deep down in ravines, near streams and in open meadows, far from tree cover. The elk would never have dared to enter these risky, hard-to-escape-from locations when wolves were near. But, unhindered by the fear of a sudden attack, they were able to browse much longer at a stretch, and they discovered a taste for new menu items. They consumed the leaves of cottonwood and willow in addition to their usual grasses. They ate more than usual. They grew fatter. They had more babies.

However, all that changed in 1995. That’s when twenty wolves were released into carefully selected sites in Yellowstone by the National Park Service and the U.S. Fish and Wildlife Service. The wolves’ presence affected the elk almost immediately. The animals became more vigilant. Repeatedly lifting their heads to scan their surroundings stole crucial time away from browsing. They changed eating locations, preferring to graze in sheltered forests rather than in open meadows—a pattern elk follow when stalked by human hunters as well.

Nowadays, about one hundred wolves patrol Yellowstone, keeping the elk on edge. The impact of fear has restored their eating to the cautious and restricted pattern so common in the wild. Ecologists have identified other animals around the world who eat less, restrict food choices, and put off eating in response to predator intimidation. Manatee-like dugongs, for example, sacrifice grazing opportunities in the underwater seagrass meadows of Australia’s Shark Bay when tiger sharks are prowling nearby. Snails in southern New England tide pools browse less on acorn barnacles and algae when they sense predatory green crabs in the vicinity. Impala and wildebeest increase their vigilance when ravenous lions and cheetahs are lurking in the neighborhood.

What’s clear is that when intimidation goes up, animals may restrict where, when, and what they eat. And when threat is reduced, eating behaviors may relax. Fear’s ancient connection to feeding could allow physicians to understand eating disorders in a whole new way. What ecologists call “encounter avoidance” and “enhanced vigilance” in wary animals might have psychiatric overlaps with “social phobia” and “perfectionism” in human patients.

Intimidation and fear take many forms in the wild. Usually, they involve claws, fangs, talons, and teeth. But there’s one threat that stalks living things without the use of a weapon or even a body. Although no one would say that animals consciously worry about it, starvation is another constant menace in the wild.

A modern supermarket is about as far from Yellowstone’s wild eating landscape as you can get. Straight aisles, stocked shelves, temperature-controlled air. I’d never thought much about animal food-storage habits,
beyond squirrels pushing nuts into the ground, woodpeckers creating “granaries” in old trees, and bees buzzing around, making communal honey. But the drive behind these behaviors connects to one of the most ominous feeding fears in the wild: starvation.

Animal larders are concealed everywhere we turn, from treetops to roots, branches to grasses, rocks, shrubs, fence posts, and eaves. They’re more plentiful and elaborate than I’d imagined, containing not just seeds and nuts but such other delicacies as twigs, lichens, mushrooms, carcasses, nectar, and pollen.

Some moles create worm farms in the walls of their burrows to keep their stash fresh and ready to eat. When they catch a worm, they bite off its head and store the body under the cool soil in special areas of their tunnels. Since moles will continue to injure and stash worms as long as they’re available, these so-called fortresses can grow quite large. One I read about weighed more than four pounds, was a yard and a half long, and contained more than a thousand earthworms and grubs. In a lovely bit of recycling, some lucky worms get a reprieve: if they can avoid being eaten until they’re regrown their lost heads, they can make an escape, especially in the spring, when the soil warms up.

During nighttime feeding runs, mountain beavers in the Pacific Northwest snip off bits of ferns and other greens and stack them in small bundles under logs and on rocks. They also hang them over the low branches of trees and shrubs. The beavers later move these piles of wilted greens into special chilled storage chambers near their nests and feed out of these “mini-fridges” all year. The moisture-laden vegetation is quick to mold, so every week or so the beavers have to take stock and replace the stores. You might go through your crisper from time to time, too, and throw out the liquefying romaine.

And lest you think food caching is limited to vegetarians or rodents, consider that birds of prey are well known to “overkill” and store food. An American kestrel was once seen slaughtering seven mice and storing their bodies in two adjacent grass clumps. A screech owl once found an empty shelf in a barn and stashed twenty-two dead day-old chicks on it. Bears, foxes, and mountain lions conceal animal carcasses under leaves and dirt, for later meals. Spiders routinely kill more insects than they can eat, package them up in take-out containers of spider silk, and go back later to consume them. Jackals were spotted returning at night to a mud pit to retrieve stored shreds of meat they’d submerged earlier in the day.

Eating alone, in the safe privacy of a personal larder, minimizes the time an animal spends in risky, high-predation situations. And a hoarder has extra energy and time for courtship and mating. But it’s hoarding’s antistarvation advantages that confer the real payoff.

With provisions to insure them against future famines, animals that hoard have a safety net to protect them from dangerous periods of food shortage. Hoarding behavior literally makes animals safe. Safety and food hoarding connect in humans, too, whether it’s a prudent stash
of dried beans and powdered milk in an emergency-preparedness kit, a pantry pleasingly stacked with tuna cans, or a freezer stocked with chicken breasts.

But psychiatrists recognize, in some hoarding behaviors, signs of underlying disturbance.
For example, food hoarding is often observed in foster children with severe attachment disorders, those whose early sense of safety has been fractured. Even the hoarding of nonfood items connects again to the ecology of fear. Human hoarders’ stacks of magazines, plastic bags, and receipts make them feel safe. Parting with these treasured items causes them distress, fear, and anxiety.

Compulsive hoarding—of food, objects, and even pets—is currently believed to be a type of OCD.
OCD is linked to several other psychiatric disorders, including anxiety and eating disorders. Clinicians know that the majority of patients with anorexia nervosa suffer from anxiety disorders, including OCD and social phobia. The connection between fear and feeding spans species: from human beings to anxious elk, stressed grasshoppers to cautious gerbils. The ecology of fear also underlies another animal syndrome, one with intriguing parallels to human patients.

It’s ironic, but answers for suffering anorexic patients may be hiding in one of the last places they might think or want to look: a pig farm. Under socially stressful conditions, some female pigs may self-restrict their food intake, even as the herd mates around them are eating normally. They continue losing weight until they’re emaciated. You can easily spot them by their prominent backbone ridges. Like human anorexics whose hair becomes brittle and patchy, pigs afflicted with a condition called thin sow syndrome grow hair that is abnormally coarse and long. Women who are anorexic often stop having periods (in fact, that’s technically part of the definition of anorexia nervosa). Thin sows stop going into heat. Members of both species can go on to starve themselves to death.