Imagine this: a purse falls off a chair in the vicinity of two seven-month-old puppies. Terrified, one of the puppies refuses to go anywhere near it. Her sister takes a look, gives it a quick sniff and then leaps over it and goes on her merry way. Scenarios like this happen every day to Holly and Kit, the Border Collie/Beagle mixed-breed pups adopted by the editor of The Bark a few months ago.
Rescued from a shelter in Kentucky early this year, littermates Holly and Kit have been in their new home in northern California for several months now. As far as is known, the pups’ first five months of life were less than ideal; they seem to have lived outside on their own and had little contact with people. Not surprisingly, they arrived at their new home timid and shy. Since then, Kit has come out of her shell, romping happily around local off-leash parks with her “big sister,” Lola. Holly is a different story; she is sweet and loving at home, but extremely skittish in other contexts. But even at home, small changes in the environment—like a purse falling from a chair—overwhelm her.
That sisters would behave differently isn’t shocking to any of us with siblings or children, or anyone who has watched one puppy battle through life while a littermate calmly accepts whatever comes her way. We all know that sisters and brothers, whether human or canine, are not clones. No matter how similar the upbringing, minor differences in siblings’ genetic make-up account for major differences in behavior. But beyond that, what do we know about what influences a dog’s approach to life? What’s new in our understanding of the ontogeny of fear? In particular, what can make a fearful dog like Holly so different from her more outgoing sister?
Genetic Blueprints. The answer begins, of course, in the genetic make-up of each dog, which is unique to that individual. After all, the point of sexual reproduction—an inefficient and messy process (genetically speaking)—is variation. Each parent contributes one strand of DNA to the double helix that makes up each chromosome, and the strands link up in unique ways each time a new life is created. Thus, every individual is the result of a unique combination of genes. In an environment with a range of conditions—perhaps a drought one year and floods the next—genetic variation ups the odds that some individuals will survive even if others perish, thus ensuring continuation of at least some individuals of their particular species.
This variation isn’t news to dog lovers—we are all well acquainted with canine physical variation, from flat-nosed Pugs to skinny-muzzled Salukis. This genetically mediated variation is equally true of behavioral predispositions. According to research done over the last 30 years on personality, one of the most heritable behavioral characteristics relates to the behavior of Holly and Kit. What is now called the “shy-bold continuum” has been found to be a relatively stable aspect of personality in rhesus macaques, cattle, people and dogs (to name a few). It appears as though different points on the “shy-bold” spectrum are advantageous at different times. For example, primatologist Steve Suomi has found that in some conditions, shy male rhesus macaques have higher reproductive success than bold ones. The shy males wait longer to leave their natal troops, and thus arrive at a new troop larger and better able to hold their own when challenged by established males. (But sometimes it helps to be brave and bold; what if there are only a few troops in the area and the bold monkeys become established in them before the shy ones venture forth?)