They've Got Personality
Long considered unscientific, studies of the dispositions of individual animals are multiplying, yielding some fascinating—and sometimes practical—results
GEORGE ARCHIBALD used to run a dating service. If his clients didn’t hit it off, the stakes were huge: the future of an entire species.
In the 1970s, Archibald, former director of the International Crane Foundation, pioneered captive-breeding programs for endangered birds like the whooping crane. So, when thinking about the perfect matches for his avian “clients,” what did the biologist consider? It sounds like an ad for eHarmony: “We looked at their personalities,” says Archibald.
Like eHarmony founder Neil Clark Warren, Archibald says superficial traits like appearance are less important than you’d think; personality is the key to a compatible couple. “Sometimes a normal bird will pair with a real gimpy bird,” he says. “And age is not important—an older bird will pair with a much younger bird.” What an extremely aggressive female needs is a male who is even more aggressive. “Unless she is submissive to the male,” says Archibald, “there is a possibility she won’t experience the hormonal changes that allow her to lay eggs.”
One definition of personality—at least as applied to humans—is “the characteristic pattern of thoughts, feelings and behaviors that make a person unique.” But can nonhuman animals also have personalities? While animal behavior is generally easy to observe and measure, assessing an animal’s “thoughts” and “feelings” is difficult at best. That’s one reason many researchers long rejected the concept of unique personalities in animals. “When I began my study of wild chimpanzees in 1960 at Gombe Stream Research Center, it was not . . . quite proper to talk about animal personalities,” wrote primatologist Jane Goodall in a 1998 essay for Science magazine.
The tide turned a little more than a decade ago. The first time scientists applied the term “personality” to a nonhuman in a major psychology journal was in 1993—in reference to an invertebrate, the octopus. Roland Anderson, a biologist at the Seattle Aquarium, noticed that keepers had vivid nicknames for the facility’s Giant Pacific octopuses. “Lucretia McEvil” tore up the fittings in her tank every night. “Emily Dickinson” was cripplingly shy. The animals seemed to have individual personalities, but could this be quantified scientifically?
Anderson and psychologist Jennifer Mather of the University of Lethbridge in Alberta, Canada, devised an experiment with a smaller species, the East Pacific red octopus. They tested how individuals responded when gently poked, startled or offered food. Each octopus, it turned out, had a unique, and consistent, set of responses—in other words, a personality.
Still, when Samuel Gosling, then a graduate student at the University of California–Berkeley, proposed studying animal personality in the mid-1990s, his advisor told him the idea was “goofy.” Gosling pressed on anyway, assessing Berkeley’s captive colony of 34 spotted hyenas using techniques from human personality evaluation. He asked the animals’ caretakers to rank them on such behaviors as assertiveness, excitability, “human-directed agreeableness,” sociability and curiosity. Though they scrupulously refrained from comparing notes, the four keepers gave very similar assessments of each hyena’s personality. What’s more, the results could not be explained as a consequence of a dominance hierarchy or the animals’ age or sex.
Gosling, who now heads up the Animal Personality Institute at the University of Texas in Austin, generally gets credit for sparking an avalanche of animal personality research over the past decade. Scientists have discovered that everything from sticklebacks to salamanders to snails have personality (if not charm)—though some researchers draw the line at the word “personality,” preferring the less anthropomorphic term “behavior syndrome.”
“Anybody who watches animals knows they vary,” says Cornell University biologist Janis Dickinson. Dickinson was first impressed by differences among individual birds while studying western bluebirds as a post-doctoral student at the University of California–Berkeley. “We were out in Carmel Valley trying to band birds,” she recalls. “We had traps that let a piece of Plexiglas fall in front of the nest box entrance after the bird was inside. Sometimes, I would make a mistake, and the bird would escape. With some birds, you’d reset the trap, stand back, and they’d go right back in the box. Other birds, once they realized something was different, would sit on top of the box with food in their beaks, but refuse to enter.”
Scientists still have plenty of questions about animal personality. For example: Is its primary source nature or nurture? Is personality fixed or mutable? And perhaps most perplexing, how can a variety of personalities be maintained in a population when evolutionary theory predicts the emergence of a single, most adaptive personality?
Renee Duckworth, an evolutionary biologist at Harvard University, is starting to address some of these questions in western Montana, where bluebird populations declined in the 1930s after logging took out big trees with woodpecker holes that had provided nest sites. In the 1980s, when a network of volunteers started putting up nest boxes, the birds began to rebound. Mountain bluebirds moved in first, but western bluebirds, which are more aggressive, tended to follow and kick them out of the boxes. Duckworth and Alex Badyaev of the University of Arizona decided to test individual bluebirds for aggressiveness—as measured by a bird’s willingness to attack a model of a tree swallow, another bird that will compete for the same nest sites.
The researchers found that the birds roaming afield, looking for new nest sites, tended to be most aggressive. Stay-at-home birds tended to be meeker. As a population became established, though, the aggressiveness of the average male declined. Why? Aggressive behavior is good for grabbing real estate, suggest the scientists, but pioneering birds make bad dads. They don’t pull their weight feeding chicks, so their offspring are less likely to survive.
A team of European scientists has been exploring the role of genes versus environment. They now have evidence for a “curiosity gene” in the great tit, a tiny songbird much like our North American chickadee. Researchers from the Max Planck Institute for Ornithology and the Netherlands Institute of Ecology released newly fledged tits into a large room with wooden perching posts, then measured how long it took each bird to perch on each post. In a separate test, they placed an unfamiliar object (a Pink Panther doll) in a bird’s cage and watched to see if the bird hung back or hopped over to check it out, and how long that took.
They also worked up each bird’s genetic profile, focusing on a gene with 73 variants, dubbed Drd4, which controls the structure of a dopamine receptor in the brain. It turns out that birds with the curiosity variant were the most willing to explore new objects. Tests of great tits in the wild have yielded the same results.
But Stephan Schoech of the University of Memphis points out that environment may also shape personality. With his students, he’s studying the effects of the stress hormone corticosterone (CORT) on Florida scrub-jays. “These birds love peanuts,” says Schoech. “But there’s this tremendous variation in how willing they are to come get one. Some jays will land right on your hand to get a peanut; others won’t come within 50 meters.” Schoech’s former postdoc, Eli Bridge (now at the University of Oklahoma), had read an article about how pregnant rats, stressed by exposure to bright lights, developed elevated corticosterone levels. Their male offspring subsequently turned out somewhat feminized—less aggressive during rough and tumble play and showing more parental care to their young. “We wondered,” says Schoech, “could something similar happen in scrub-jays?”
Schoech’s team watched mother birds on the nest to evaluate how attentive they were, specifically time spent brooding and how far from the nest each female traveled. Shortly after, they took blood samples from baby jays to measure CORT—and found the highest levels in nests with the least attentive mothers. About seven months after the birds fledged, they trained the jays to come to a pile of shelled peanuts, then rigged up a series of tests to gauge each bird’s boldness. (In one, for example, a buzzer sounded when a bird approached the peanuts, and researchers measured how long it took the startled animal to return.) Though the researchers have tested just ten birds so far, “we were blown away when we dug up the CORT data,” says Schoech. “CORT levels in nestlings predicted how fearful birds were some seven months later.”
Personality research is more than an esoteric exercise. It helps biologists like Archibald successfully breed endangered species. It also helps scientists reintroducing endangered animals to habitats where they’ve been extirpated. In Bakersfield, California, for example, Samantha Bremner-Harrison of California State University–Stanislaus screens the personalities of San Joaquin kit foxes before choosing which individuals from an urban population she’ll reintroduce into wild habitat.
Fisheries managers might also take personality into account. Take the case of the codfish. Fisheries biologists are scratching their heads about why populations off the coast of Newfoundland haven’t recovered since the Canadian fishery closed to commercial harvest in 1992. “I think there’s a hidden mechanism of selection against fast-growing fish, and that is behavior,” says Peter Biro of the University of Technology in Sydney, Australia.
Fast-growing fish need lots of food, argues Biro, so they have to be both active and bold. But that behavior makes them more likely to be caught in gill nets. “So, over time, virtually all the fast-growing fish have been removed. That selected for a population with a slower growth rate.” And indeed, data show that for the cod that remain, growth rates are half what they were historically. “It’s not enough to institute minimum size limits if you have a population with variable personalities because you will differentially remove one personality type, ” says Biro. “Personality,” wrote F. Scott Fitzgerald in The Great Gatsby, “is an unbroken series of successful gestures.” Fitzgerald’s narrator, Nick Carraway, was speaking of the elegant Gatsby, but the principle also applies in the natural world: Personality is a series of gestures, or behaviors, that can tip the scales to survival.
Pennsylvania journalist Cynthia Berger wrote about the impact of global warming on Canada’s gray jays in the February/March 2008 issue.
Spineless Minds: The Character of Spiders
Anyone who’s ever lived with a dog or a cat probably accepts the fact that animals like lions, gorillas and foxes can have unique personalities. But insects and spiders? Scientists are indeed discovering that a variety of spineless creatures, from water striders to crickets, exhibit “behavioral syndromes” that by most definitions would qualify as personality.
Take funnel-web spiders. For many years, biologist Susan Riechert of the University of Tennessee–Knoxville and her colleagues have been studying two populations of the same species of these spiders, one along a wooded riverbank in Arizona and the other in a dry New Mexico grassland. They’ve discovered that individual spiders from both groups tend to behave in consistent, predictable ways—they are either bold or timid toward potential predators, prey and competitors of the same species. The researchers also found that more spiders in New Mexico act aggressively than do their Arizona counterparts. The difference makes sense: While woodlands harbor more predators that may pick off the boldest spiders, desert grasslands support less insect prey, meaning that timid spiders might starve.
How Bold Are Your Birds?
Backyard birders nationwide are helping researchers at the Cornell Lab of Ornithology study the personalities of eastern, western, and mountain bluebirds, tree swallows, black-capped chickadees and other cavity-nesting species. By signing up for NestWatch, a national nest monitoring project sponsored by the lab, volunteers can participate in its “Personality Profiles” experiment by attaching a harmless novel object, such as a checkered bow, to the outside of a nest box, then watching and recording how the birds respond. Will they be cautious or curious? “We believe that examining avian reactions to novel objects can help us understand why some birds respond well and others poorly to human disturbance,” says biologist Janis Dickinson, director of the lab’s citizen science programs. To find out more, go to www.nestwatch.org.—Laura Tangley