Meeting Abstract
The broad diversity in morphology and geographic distribution of the 35 free-ranging members of the family Canidae is perhaps only rivaled by that of the domesticated dog, Canis familiaris. Considered to be among nature’s most elite endurance athletes, both domestic and wild canids provide a unique opportunity to examine the limits of mammalian exercise performance and energy expenditure. These animals exhibit peak aerobic performance roughly three times greater than those of equivalently-sized mammals. To explore the effect of artificial selection on running gait and efficiency, we investigated the kinematics and energetics of three large (>20kg) dog breed classes (northern breeds (n=7, 35.2±11.6 kg), scent hounds (n=5, 24.8±1.78 kg), and retrievers (n=5, 35.5±2.5 kg)) representing relatively strong, medium, and weak artificial selective pressures for endurance tasks, respectively. By filming all individuals moving freely along a 10m level transect, distinct kinematic relationships for preferred gait transition speeds, stride frequency, and stride length emerged for each breed class. A subset of dogs within each class was successfully trained for treadmill metabolic trials to measure oxygen consumption (VO2, mL O2∙kg-1∙min-1) during steady-state exercise across a range of speeds. Though each class showed linear increases in VO2 with running speed, mass-specific transport cost (COT, J∙kg-1∙m-1) was significantly lower for northern breed dogs than hounds or retrievers (ANCOVA F5,144 = 24.02, p<0.001) for speeds greater than 0.6m∙s-1. These results suggest that intensive artificial selection for endurance running in certain domestic canids confers an energetic efficiency perhaps similar to that of their wild, cursorial ancestor Canis lupus.
