Understanding sex differences in the cost of terrestrial locomotion

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Lees, John J., Nudds, Robert L., Folkow, Lars P., Stokkan, Karl Arne, Codd, Jonathan R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Energetics; Evolution; Locomotion; Sexual dimorphism; Sexual selection; Svalbard; Lagopus muta; Lagopus muta hyperborea
• Online Access: https://research.manchester.ac.uk/en/publications/8b6762ef-42c8-447e-8740-9e0eb6b0f515; https://doi.org/10.1098/rspb.2011.1334; http://rspb.royalsocietypublishing.org/content/279/1729/826.full.pdf#page=1&view=FitH

Little is known regarding the physiological consequences of the behavioural and morphological differences that result from sexual selection in birds. Male and female Svalbard rock ptarmigans (Lagopus muta hyperborea) exhibit distinctive behavioural differences during the breeding season. In particular, males continuously compete for and defend territories in order to breed successfully, placing large demands on their locomotor system. Here, we demonstrate that male birds have improved locomotor performance compared with females, showing both a lower cost of locomotion (CoL) and a higher top speed. We propose that the observed sex differences in locomotor capability may be due to sexual selection for improved male performance. While the mechanisms underlying these energetic differences are unclear, future studies should be wary when pooling male and female data. © 2011 The Royal Society.