Variation in body condition of migratory caribou at calving and weaning: Which measures should we use?

Abstract

Abstract. Monitoring the body condition of ungulates is often considered an efficient way to assess habitat quality. It is therefore essential to select adequate measures to describe individual body condition. Because there is no consensus on which measurement(s) can best describe individual variability in body condition, field biologists often measure several variables, increasing processing time. From 2007 to 2009, we assessed body condition of female-calf pairs in 2 herds of migratory caribou in Northern Quebec/Labrador, Canada, using multiple measurements of size, mass, and fat depth. We sought to identify, using multivariate analysis, which measurement(s) had the greatest influence on a composite measure of body condition of females and calves at calving and weaning. Our results indicate that adult females are best described with a body bulkiness index opposing heavy and long/round-bodied females with high body protein reserves to light and short/ slender-bodied females with low body protein reserves. At weaning, adult females can also be differentiated by a body fat index opposing fat to lean females. Calf body condition is best described by mass at birth and by a combination of mass and size measurements at weaning, opposing heavy and tall individuals with high protein reserves to light and short ones with low protein reserves. Overall, body mass appears to be the measurement that best describes individual variability in body condition of females and calves at calving and weaning. Our systematic comparison of body condition measurements will provide field biologists with guidance for future data collection.