Litter Mate Behavioral Variation: A Multi-Ingredient Stew
By Myrna Milani, BS, DVM
(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, 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. Second, this extended mating period means that some pups may spend several more days developing than others. Third, 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, a pup then faces a whole new set of environmental circumstances that test the range of its genetic capacity. For example, we can safely say that certain behaviors—such as the freeze, fight, or flee fear responses—evolved to provide the wild dog with the widest range of options when threatened. We can also understand how it would benefit the dog to use one approach more than another in certain situations. A mother with pups who chooses to fight to protect her off-spring will have a better chance of adding her genes to the canine gene pool than the female who flees when a predator attacks 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 taking this approach.
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 things 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 the animal's desire to protect them rather than its fear. Needless to say, though, when a strange dog displays a fear-based fight response toward those same people, they 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.
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 such inherent behaviors may lessen a husky or malamute's chances of survival in upscale suburbia.
In all of these situations, how the owner interprets the dog's behavior 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.
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