The pace of life under artificial selection: personality, energy expenditure, and longevity are correlated in domestic dogs.

The domestic dog has undergone extensive artificial selection resulting in an extreme diversity in body size, personality, life-history, and metabolic traits among breeds. Here we tested whether proactive personalities (high levels of activity, boldness, and aggression) are related to a fast "pace of life" (high rates of growth, mortality, and energy expenditure). Data from the literature provide preliminary evidence that artificial selection on dogs (through domestication) generated variations in personality traits that are correlated with life histories and metabolism. We found that obedient (or docile, shy) breeds live longer than disobedient (or bold) ones and that aggressive breeds have higher energy needs than unaggressive ones. These correlations could result from either human preference for particular trait combinations or, more likely, correlated responses to artificial selection on personality. Our results suggest the existence of a general pace-of-life syndrome arising from the coevolution of personality, metabolic, and life-history traits.