The Genetics of Behavior

USBCC Newsletter, Winter 1994

I've written in previous issues about the inheritance of normal color variations and of simple and complex genetic defects. I've talked about deliberate selection and about accidental "drift" and their effects on a whole population of animals. But the bottom line in breeding Border Collies is something else--the something we call instinct. What is it? To what extent is it inherited? Can those other breeds of dogs really learn to herd?

Instinct: Instinct is an old word, referring to inborn behaviors. It is the province of the zoologist, studied in depth by Nikko Tinbergen and Konrad Lorenz. Tinbergen's studies involved birds and their complex social behavior. What he found was that every bird in a particular species has certain inflexible patterns of behavior, reflex responses to very specific stimuli. A gull, for example, recognizes its own egg only if the egg is in its nest. Pick the egg up, move it a little way off in the sand, and the bird doesn't know what it is. It falls instead for various forms of fake eggs placed in the nest--they may be square instead of egg-shaped--so long as the fake object is the color of the natural egg. In Tinbergen's world of instinct there is no learning, only the inborn patterns.

Psychologists, historically, have preferred to think that all behavior is learned, and that early childhood experiences can explain everything. The more modern animal behaviorist comes down somewhere in between, and the herding "instinct" of the Border Collie is also somewhere in between.

The genetics of behavior is a very difficult subject to study; most work has been done on rats and mice running mazes, and most of it isn't very helpful to a dog breeder. One fact that keeps coming out, though, is that various types of behavior can be changed by selective breeding.

Dog Behavior: One of the most comprehensive studies, interestingly enough, was done on our own favorite species, the domestic dog. It was done at the Jackson Laboratory in Bar Harbor, Maine, by John Paul Scott and John L. Fuller. For a period of thirteen years, Scott and Fuller bred, raised, and tested hundreds of purebred and deliberately crossbred dogs, studying the development of their behavior from birth to one year. They set out to ask not "Is behavior inherited," but "What does heredity do to behavior?" The answers are contained in a frighteningly detailed (and hard to find) book titled Genetics and the Social Behavior of the Dog.

Five breeds of dogs were involved in the tests: Basenjis, Beagles, American Cocker Spaniels, Shetland Sheepdogs, and Wire Haired Fox Terriers. They were chosen for their small size, to fit into a limited physical facility, and to represent the various groups of dog breeds.

When Gregor Mendel first defined genetics, he tested very simple all-or-nothing traits (tall/short; green/yellow, etc.). He made several different types of crosses: purebred x purebred; hybrid x hybrid; hybrid x purebred. In classic "Mendelian" tests, Scott and Fuller also selected simple behaviors. A large variety of behavioral tests and measurements were made of the dogs--puppies, really--over their first year. Overall, the Basenji and the Cocker Spaniel showed the greatest differences, so crosses were made between them and measurements repeated on their puppies, on a second generation bred from those hybrid puppies, and on others that were the result of breeding the hybrids back to the parent breeds.

Their book takes several hundred pages to tell the whole story, but certain of their results were particularly relevant to breeding performance dogs. In almost every characteristic tested, there was a particular time in the development of the puppy at which the behavior appeared, and the conditions at that time influence the development. In the standard conditions of the lab, for instance, pups were handled little except for being fed, up to five weeks of age. This was enough in most of the breeds to make the pups comfortable about humans, but the Basenjis were fearful unless handled much more. They responded to more frequent handling as late as seven weeks. The few pups that were hand raised showed no breed differences. Others that were raised in more "wild" conditions also showed no breed differences: all were wild and shy of humans. The genetic difference, then, between the Basenjis and others is not between "shyness" and "boldness" but is a difference in the amount of handling needed to socialize them.

This genetic effect on a threshold of behavior was typical of many of the tests performed. Basenjis are known as a breed that doesn't bark; Cocker Spaniels are infamous barkers. But even Basenjis will bark; they merely need to be more strongly stimulated. The trait of being easily stimulated to bark, as exhibited by the Spaniel, is dominant and shows statistical inheritance close to what would be predicted for a single gene (like the red color gene I talked about before).

A slightly more complicated behavior pattern might be more interesting in the Border Collie context. We have a pretty good idea that the Border Collie's tendency to lie down and stare at sheep, rather than to stand like its pointer/setter ancestors, comes from early Spaniels. These dogs were selectively bred, before anyone knew anything about genetics, to crouch and lie still when they located birds in the field. Many Spaniels still show this behavior.

One of the regular procedures in the genetics lab was a weekly weighing of the pups. Each one was put on a scale for one minute and "trained" to be quiet. By the age of eleven weeks, 70 percent of the Cockers were quiet on the scale; only 20 percent of the Basenjis. The very young pups would crouch or lie down on the scale, but as they got bigger there was not enough room. At this point the Cockers would begin to sit; the Basenjis to stand.

By sixteen weeks, 70 percent of the Spaniels would sit on the scales; 90 percent of the Basenjis would stand. The whole behavior of lying or sitting quietly could be separated into these two different traits: lying/standing, and quiet/active. In the crossbreeding experiments, these behaviors could be separated, so that there were pups that were quiet but preferred to stand, or would sit, but didn't like to be quiet.

The crouch itself could be shown to be controlled by two major genes, with the crouch (or sit) dominant over the stand. The quiet attitude was also controlled by two genes, with the Spaniel behavior (quiet) recessive to the more active. The whole pattern of quietly crouching, then, results from four genes altogether. The number of different genetic combinations that can be formed from 2 (2-factor) genes is 256!

The Border Collie: What does all this mean to the Border Collie? Imagine, if that simple quiet crouch behind the sheep depends on four separate genes, what must be involved in the entire collection of herding behavior: eye, balance, power, bidability, etc. And what must the chances be of accidentally combining the right factors to remake a herding dog, if those combinations are ever lost?

The complexity of the genetics of behavior is probably not a surprise, but it is the basis of the entire argument that the performance dog must be bred for performance at every generation. The more genes are involved, the more different combinations are possible, the more easily they become separated and lost.

If the dogs selected for breeding for conformation are not the ones with the best herding genes, the population will inevitably drift away from the wonderful performance combinations that have been selected in the breed for so many generations.

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