Can individual behavior in wildlife be called personality?
A story by Pennsylvania journalist Cynthia Berger in the latest issue of National Wildlife has shed new light on an old discussion concerning individual differences in animal populations. Berger chronicles several scientific experiments on captive wildlife that may explain variant behavior among animals of the same species and family.
Those of us who observe wildlife tend to agree that individuals of the same breed often have differences as pronounced as human personality.
Science, however, has discounted most of these accounts as “anthropomorphizing” wild animals. Even primatologist Jane Goodall has noted that when she began her study of wild chimpanzees in 1960, it was not considered proper to talk about animal personalities.
That may be changing with genomic mapping and the discovery of certain genes that correspond to personality traits. In humans, personality has been defined as “the characteristic pattern of thoughts, feelings and behaviors that make an individual unique.” While animal behavior is generally easy to observe and measure, assessing an animal’s thoughts and feelings is difficult at best, Berger writes.
Some researchers still draw the line at the word “personality” preferring the term “behavior syndrome” and posit that personality in nonhumans may be just a unique and consistent set of responses to stimuli.
Terminology aside, those who have raised and trained animals, likely would agree that individuals show many differences in personality, often from birth, that cannot be attributed to dominance hierarchy, or societal pressure, common in wolves and other canids, evolved to assure survival of the pack.
The thing most puzzled over is whether the primary source is nature or nurture, and if personality is fixed or mutable. Scientists wonder how a variety of personalities can be maintained in a population when evolutionary theory predicts the emergence of a single more adaptive behavior.
A team of European scientists exploring the role of genes versus environment found evidence of a “curiosity” gene in songbirds. They worked up each bird’s genetic profile focusing on a gene with 73 variants dubbed Drd4, Berger cites, which controls the structure of a dopamine receptor in the brain.
Another possibility for personality differences from birth may be the stress hormone corticosterone, or CORT. Blood samples from baby scrub jays showed the highest CORT levels in those of inattentive mothers. CORT levels in nestlings predicted how fearful the birds would be seven months later.
In a study of pregnant rats, those stressed by exposure to bright lights developed elevated CORT levels. Their male offspring turned out somewhat feminized, Berger writes, less aggressive at play and later showing more parental care to their own young.
Some of this research has been helpful in restoring populations of endangered species. Scientists screened the personalities of San Joaquin kit foxes before choosing which to reintroduce into wild habitat.
I can’t help wondering if similar selection was made when introducing captive-raised California condors into the wild. The ones that were released in the mountains near our ranch weren’t particularly bright and got into all sorts of trouble.
It seems those juvenile condors had the curiosity gene in spades, but not enough street smarts to stay out of trouble. Some scientists believe that as scavengers living on road kill and gut piles left by hunters, the condors ingested enough lead to kill most of the limited brain cells they started with. Good point.
It should be noted that in raising cattle dogs the pick of the litter was rarely the largest or the one showing dominant behavior. It was the one who noticed when a horse was led into their yard. All of the littermates were of the same gene pool, raised in the same environment, subjected to the same stress hormones in utero, and during their first weeks had no physical contact with humans. So why does one crouch, growl and charge the horse while they others keep playing? Can we rule out the curiosity gene and call it personality? And if so, where does that personality come from?
Wild birds are another matter. It’s hard to tell one from another except for gender.
We usually had two or three pair of red-tailed hawks and about five pair of ravens living in our canyon. For the most part, their personalities were indistinguishable. But there was one female hawk that was different. She was very vocal, curious and when I was in the garden, she was always nearby.
One summer, after her two hatchlings had fledged, I saw her jumping up and down near the pump house and crying out. The next day, I saw feathers on the ground and realized her mate had died and probably was taken away by coyotes. She was distressed for some time. Then one day I saw her bathing in a sprinkler and preening. After awhile she flew over the garden and disappeared. A few weeks later, she returned with a new mate. He sat in her oak tree and watched as she flew back and forth over the garden calling. I went outside and watched this amazing display. The male seemed completely disinterested. At sunset, they flew away together and I never saw her again.
A friend who trains falcons agreed that her behavior was unusual. But then, she’d always been different. Wild or not, I’d have to call that personality.