Litter Mate Behavioral Variation: A Multi-Ingredient Stew

(Originally written for DogWatch, a newsletter for the general public from the Cornell University College of Veterinary Medicine)

Two friends and I all got pups from the same litter and we all took them to puppy kindergarten and obedience class. Now my dog Skeeter is totally trustworthy with everyone and obedient most of the time. However his litter mate Zip acts really edgy around certain people even though he’s very obedient. The third dog, Clyde, is afraid of everything. How can three dogs with the same background turn out so differently?

Even though the battle over whether genes or the environment determine how organisms respond physiologically and behaviorally has raged for decades with no end in sight, fewer and fewer scientists consider this an either/or situation. Most recognize that a combination of genetic and environmental factors contribute to how a particular individual develops. The wild animals most likely to survive are those who possess that combination of physical and mental characteristics that allow them to succeed in their particular environment. Behavior in domestic animals, and especially in our pets, always must take into account the effects of the human-animal bond too.

Additionally the interplay between genes and environment that might explain the differences among litter mates begins on a cellular level even before the pups are born. Because female dogs remain receptive to males for a week or more, pups in the same litter may have different fathers, a process known as superfecundation. This extended mating period also means that some pups may spend several more days developing than others. Additionally studies indicate that an animal’s position in the uterus may determine how the maternal hormonal changes associated with the process will affect that pup’s physiological and behavioral development.

Once born, the kind of the maternal and human care a particular puppy gets for how long also may influence genetic expression.  At the same time puppies also face a whole new set of environmental circumstances that test the range of their genetic potential. For example, we can safely say that certain behaviors—such as the freeze, fight, flee, or tend/befriend fear responses—evolved to provide wild canines with the widest range of options when threatened. We also can understand how it would benefit dogs to use one approach more than another in certain situations. A mother with pups who chooses to somehow manipulate a perceived threat using a tend/befriend approach to protect her off-spring will have a better chance of adding her genes to the canine gene pool than the female who tries to freeze, fight, or flee when a predator attacks her or her young. On the other hand, single dogs smart enough to freeze or flee rather than fight a larger predator could both conserve energy and prevent injury to themselves by using this strategy.

Although the checks-and-balance system that results from the interplay of genetic potential and environmental challenge works beautifully in the wild, domestication and the human-animal bond can complicate matters enormously. Many people view the fear responses emotionally and project those emotions onto their pets’ behavior. Some owners see the fight response as “courageous” and praise the dog for displaying it, mistakenly thinking it communicates these animals’ desire to protect those people rather than the dogs’ fears. Needless to say though, when a strange dog displays a fear-based fight response toward these same people, the majority will see it as far more hostile than brave!

Dogs who freeze or flee tend to evoke two quite opposite human emotions, too. Some people feel so sorry for these animals, they want to baby them. Others see the freeze and flee responses as “cowardly” and want to punish the animal who responds this way.

Clinical experience causes me to believe that many fearful/stressed dogs opt for the tend/befriend response because they perceive this are their only viable option. If they’re confined in a house, care, behind a fence, or leashed to tied, they can’t run. If their fear causes them to drool, pee, poop, or empty their anals glands,  they eliminates freeze. And if they have neither the desire nor the ability to fight, that only leaves the tend/befriend. In some ways this response has the most negative consequences for dogs because many people associate their stressed attention-seeking and -keeping behaviors (such as jumping leaning, bring toys, etc.) with love.

In addition to these most fundamental survival behaviors hardwired into all dogs, we can add all those related to specific breeds. Digging shallow cooling holes and a sophisticated vocal communication system served the primitive northern breeds very well in the environments they were bred to work in. However a predilection for such behaviors may lessen a husky or malamute’s chances of survival in upscale suburbia.

In all of these situations, how people interpret the canine behaviors will influence how they relate to the dog; and how they relate to the dog will influence the dog’s behavior. Put another way, the relationship between the genes and environment is dynamic rather than written in stone. So if you don’t like the way your Clementine behaves, don’t blame it on her genes or her environment. Instead, use your knowledge of both to help her become the pet you want her to be.