Of Mice and Mania

My own brain is to me the most unaccountable of machinery—always buzzing, humming, soaring roaring diving, and then buried in mud. And why? What’s this passion for?
—Virginia Woolf^[1]

If you give a mouse a haircut, he might want another. And another. And another. And it’s not actually a haircut. It’s a pluck. Sometimes a nibble. When a mouse goes to a barber, he or she loses some whiskers or some fur. And usually it happens again and again.

Barber mice, as they are known, remove the fur or whiskers of other mice (and somewhat less frequently, their own). They tend to be female, but aren’t always. And they are, as far as I can tell, only to be found among captive mouse populations, be they in laboratories or pet owners’ homes. The online message boards for mouse-rearing humans (who raise them as pets or for “fancy” mouse shows) are full of hair removal stories. They post photos of mice and rats with little bald spots on their heads, reverse mohawks, or hairless facial patches shaped like tiny Phantom of the Opera masks. Perplexed, the rodents’ keepers ask questions like, “Tache seems unable to go more than two weeks in a cage with other mice without beginning to barber again. … Today I returned her to the big tank with Pu Manchu and Mrs. Beach … but I expect by the end of two weeks she’ll be barbering again. How to solve this problem?”^[2]

Some fanciers and breeders claim the behavior is about displaying dominance (i.e., the barbering mouse is boss). Others say it happens because of overcrowding or lack of stimulation: a lab mouse—even if it is born and bred to be one—still has sensory, social, and environmental needs that a cage, even a pleasant one filled with exercise wheels and colorful plastic tunnels, will have difficulty providing. What is not debatable is that barbering is simply normal grooming behavior gone awry. Usually mice groom by scratching themselves with their hind feet, washing their face or fur with their front paws (using their own saliva), and smoothing or cleaning their hair with their teeth. Barber mice take these behaviors in a more extreme direction by removing hair on others (and sometimes themselves) with their teeth. Barber mice don’t usually injure the mice whose fur or whiskers they nibble or pluck. In fact, it seems that their clients may enjoy it—that is, they will sometimes follow the barber mouse around until she or he plucks them—even when what results is the complete loss of whiskers or an unironic mouse mullet.^[3]

Given their extensive experience with mice in the laboratory, a few researchers have suggested that the barbering rodents might help us better understand overzealous hair removal in humans.^[4] In people, repetitive hair pulling (which leaves pluckers with bald spots and sometimes even interferes with their daily life) is diagnosed as trichotillomania.^[5] Not unlike mice, most human pluckers are female. The disorder affects roughly 1.5% of men and 3.5% of women in the United States,^[6] though trichotillomania may be far more widespread than we think because people are often embarrassed by their bald spots and can be quite good at covering them up. Studies using mice as stand-ins for human pluckers have tried various techniques to get the mice to start barbering in the first place (that is, if they haven’t started doing it themselves) and investigated the effects of antidepressants on the behavior. The fact that humans tend to pluck themselves and mice tend to pluck each other hasn’t stopped the use of mouse experimental models—since both the barber mouse and her client engage in the process by choice, even when it must be somewhat painful, researchers have tended to assume, for better or for worse, that the behavior found in a single human being is simply spread between two individual mice.

In humans, the most common sites of plucking are the scalp, eyebrows, eyelashes, beard, and pubic area. People may start plucking one specific area, like eyebrows, but then, over time, switch to pulling from another region. Sufferers say that the plucking is usually preceded by some sort of tension that the pull itself releases, though it can also happen when people are relaxed or distracted (i.e., when reading a book or watching television).^[7] Nevertheless, anxiety, anger, and sadness often do increase the urgency and frequency of hair pulling.^[8]

There is still a good deal of confusion about how the disorder should be classified. The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders IV (DSM) has situated hair plucking under “Impulse-Control Disorders Not Elsewhere Classified” and counsels that this behavior should not be considered a compulsion. Unless plucking is associated with obsessive thoughts, the DSM stresses that it is also not an obsessive-compulsive disorder (since the plucking is not usually performed along a framework of rigid rules in the way that obsessive-compulsive hand-washing or lock-checking can be).

The DSM’s claims notwithstanding, the behavior often does resemble a habit, an addiction, a tic, or an obsessive-compulsive disorder. More recently, researchers have begun to view it as part of a family of “body-focused repetitive behaviors,” along with skin picking and nail biting.”^[9] Whatever its etiology, trichotillomania is in the DSM because most people don’t do it. We need our hair for all sorts of reasons, some physiological, most not. Bald patches or missing eyebrows may make social situations more awkward and the time spent plucking may interfere with other things in one’s life. The habit might be a symptom of anxiety or depression, but mostly it just makes the sufferer look odd and this is when it tends to be diagnosed. Some trichotillomania sufferers, particularly children, may pull hair from other people, or even pets. And it is common for people to either play with, or eat, their plucked hairs.^[10]

In this, like so many of our neuroses, we are not alone. Hair pulling has been reported in six different non-human primate species, and, in addition to mice, has been observed among rats, guinea pigs, rabbits, sheep, musk oxen, dogs, and cats.^[11] Just as with mice, researchers who conducted a study on feather-plucking parrots suggested that they would be a good experimental model for trichotillomania-suffering humans.^[12] And like overgrooming dogs (who will sometimes lick themselves bare and oozy, a condition diagnosed as Acral Lick Dermatitis), birds have been treated with the same drugs used to treat compulsive behaviors in humans.

For captive gorillas, the most common sites for hair plucking are forearms or shins, but I have seen plucked patches wherever the apes can reach. Gorillas, unlike us, can pluck almost anywhere since they have more and thicker body hair than we do. Some gorillas, like some people, eat their hair after plucking it.

As primatologists such as Frans de Waal and Jane Goodall have observed, nonhuman animals can and do have culture, defined here as knowledge passed down from one generation to another or passed from one group to another, as in the famous case of Japanese macaques (Macaca fuscata) teaching one another to wash and season their yams in the ocean because the salted yams tasted better.^[13]So it may be with plucking—both in people and other animals. The babies of gorillas who pluck often turn out to be pluckers themselves. And troops that have never exhibited plucking sometimes start when a new plucker arrives in their midst. At the Franklin Park Zoo in Boston, none of the gorillas pulled out their hair until two young males—Little Joe and Okie—arrived in 1997 from Cleveland Metroparks Zoo. Within months, a number of the troop members in Boston were plucking.

Just as in humans, no one knows exactly why gorillas do it—except that, as it does for us, plucking may offer some sort of psychic balm or release of tension and it may be greatly influenced by one’s environment.^[14] There also may be a genetic component. An experiment conducted in 2002 demonstrated that mice bred without a group of key developmental genes (including the Hoxb8 gene, fundamental in the development of immune cells called microglia found in the brain) became severe self-barbers. The mutant mice didn’t stop at hair trimming and whisker plucking but also used their paws to scratch bald spots and sores on their rumps. A later study, published last May in the journal Cell, transplanted bone marrow (containing healthy microglia cells) from a group of control mice into the population of barbers. Four weeks after the transfer, when the new microglia had made it to the mutant mouse brains, many of the barber mice (who had been using their teeth to pluck the hair on their own chests, stomachs, and sides) stopped over-grooming. In three months, their hair had grown back.^[15] While no one is suggesting that human trichotillomania sufferers sign up for bone marrow transplants anytime soon, researchers are trying to understand the links between the brain’s immune system and the expression of mental disorders such as trichotillomania, OCD, autism, and depression.

Like the Hox genes themselves, overgrooming behaviors may be present, in some form or another, in all vertebrates with something to pluck, lick, or pull out. While such behaviors are probably not attributable to genetics alone, a predisposition to over-grooming may exist in certain individuals, who when exposed to the right combination of stressors exhibit such behaviors. Within the avian veterinary literature, feather plucking—termed “Feather-Picking Disorder” or “Feather Destructive Behavior” if it is unrelated to a separate medical condition, such as allergies—can stem from boredom, frustration, and stress, or be related to sexual behavior, premature weaning, attention seeking, overcrowding, separation anxiety, and/or changes in routine. Virtually anything that could be upsetting to a parrot can trigger the behavior.

Phoebe Greene Linden has lived with parrots for more than twenty-five years and is an expert on captive parrot behavior—fielding questions from hundreds of parrot owners online and in person. She claims that “solutions to stopping feather destructive behavior are as individual as strategies tailored for human individuals. Enriching their environments and helping them learn new behaviors when the parrot is healthy, ready to learn, physically active and mentally engaged, is best. And making sure that they have opportunities to fly, forage, and socialize is key.”^[16] However, in chronic cases, SRRI’s like Prozac have been useful, as have Xanax, Valium, and other medications.

A group of cockatoos who plucked their feathers responded (albeit somewhat unevenly) to Clomipramine, a tricyclic anti-depressant sold under the brand name Anafranil and most often prescribed to humans as an anti-obsessional medication.^[17] Another study on both plucking cockatoos and African greys tested their response to a different antidepressant, Doxepin (it worked, but not uniformly, for most parrots involved in the study). And veterinary staff at the Tufts Animal Behavior Clinic in Massachusetts documented the marked effect of SSRI’s like Prozac on feather picking in Amazonian, African grey, and Eclectus parrots.^[18]

The question underlying all of this—especially the experiments on over-grooming mice, birds, cats, dogs, and other nonhumans—is whether or not these animals’ behaviors can actually shed light on ours. Just because plucking in mice, gorillas, or cockatoos resembles our own, does it mean that the nonhuman in question is having similar thoughts? Of course, we cannot know. Even in the realm of human relationships, we all know that just because you ask a person what they’re thinking or how they’re feeling doesn’t mean that they’ll be able to tell you—they may not know why they’re pulling their hair out, or even how they feel when they do it.

Shared language in no way guarantees revelation between two beings. Just as we seek to understand mental states in humans who can’t (or won’t) talk to us, I believe we should do the same with other animals. Critics may consider this just another form of anthropomorphism, but I think that is far too narrow a view. We have long looked to other animals to better understand ourselves—using them as experimental subjects, objects of philosophical inquiry, companions with whom we soothe or challenge ourselves, or as the raw material of moral lessons. Human relationships with other animals continue to center around observations and a certain amount of projection is inherent to the act of watching and interpreting what other animals are doing with their time. Our lives with other creatures are rife with instances of both good and bad projections. A human who takes Spot to the door on a rainy afternoon might see the dog pause at the threshold, nose in the air. Depending on the person, this might be understood to mean, “Spot hates going outside in the rain and so I should buy him a cute little slicker and set of rain boots so that he’ll go out without a fuss.”

Within the scientific community, fear of projections like this one have sometimes crippled our understanding of shared animal experience. Anthropomorphism, or the attribution of “human” characteristics to nonhuman animals or objects, has been something of a dirty word in the behavioral sciences. Such fears have long informed studies such as one I once worked on in southeast Alaska. We were observing grizzly bears and their interactions with human fishermen along a salmon stream in Katmai National Park. The same bears came back summer after summer to fish, bicker, and raise their cubs and were easily recognizable by their scars, fishing styles, and personalities. And yet, as researchers, we were instructed only to use numbers to refer to the bears lest our use of human names for them might cause us to attribute human desires and thoughts to the bears as well. But outside of our official survey forms and notes, we all used names for them, like “Diver” for a bear who was fond of diving to the bottom of the river to catch his salmon. As far as I know, calling him Diver did not encourage us to assume that he was engaged in anything but bearish behavior—but that was the concern.

Thankfully, such practices have begun to change somewhat. The Stanford neuroscientist Robert Sapolsky, for example, has long used Biblical names to refer to individual baboons he studies in Kenya. Despite the holy handles, his work has not suffered and neither has that of the numerous other scientists who have more recently veered into what may have, not long ago, seemed like anthropomorphic territory. In Sapolsky’s case, it may even have helped—getting to know the personalities of his individual baboons, on their own terms and his, may have encouraged him to make the leap that their stress responses approximated our own, research that has since revolutionized how we think of the affects of chronic and acute stress on the human brain.

Projecting, in and of itself, is not a problem. And if this wasn’t true, animal models for mental disorders from trichotillomania to depression would simply not be as present in the scientific literature as they are. This isn’t to say they aren’t problematic. We cannot assume that a rat=parrot=dog=human. But if it sounds like a duck, walks like a duck, and plucks like a human—it just may be a duck we can identify with.