Remarkablemuscles, remarkable locomotion in desert-dwelling wildebeest.

Nancy A Curtin,Maja Lorenc,Stephen J Amos,Timothy G West,Tatjana Y Hubel,Anthony R Gardner-Medwin,John C Lowe,Hattie L A Bartlam-Brooks,Alan M Wilson,Emily Bennitt

doi:10.1038/s41586-018-0602-4

Abstract

Large mammals that live in arid and/or desert environments can cope with seasonal and local variations in rainfall, food and climate1 by moving long distances, often without reliable water or food en route. The capacity of an animal for this long-distance travel is substantially dependent on the rate of energy utilization and thus heat production during locomotion-the cost of transport2-4. The terrestrial cost of transport is much higher than for flying (7.5 times) and swimming (20 times)4. Terrestrial migrants are usually large1-3 with anatomical specializations for economical locomotion5-9, because the cost of transport reduces with increasing size and limb length5-7. Here we used GPS-tracking collars10 with movement and environmental sensors to show that blue wildebeest (Connochaetes taurinus, 220kg) that live in a hot arid environment in Northern Botswana walked up to 80km over five days without drinking. They predominantly travelled during the day and locomotion appeared to be unaffected by temperature and humidity, although some behavioural thermoregulation was apparent. We measured power and efficiency of work production (mechanical work and heat production) during cyclic contractions of intact muscle biopsies from the forelimb flexor carpi ulnaris of wildebeest and domestic cows (Bos taurus, 760kg), a comparable but relativelysedentary ruminant. The energetic costs of isometric contraction (activation and force generation) in wildebeest and cows were similar to published values for smaller mammals. Wildebeest muscle was substantially more efficient (62.6%) than the same muscle from much larger cows (41.8%) and comparable measurements that were obtained from smaller mammals (mouse (34%)11 and rabbit (27%)). We used thedirect energetic measurements on intact muscle fibres to model the contribution of high working efficiency of wildebeest muscle to minimizing thermoregulatory challenges during their long migrations under hot arid conditions.

Highlights

We set out to test the hypothesis that wildebeest undertake long-range locomotion from grazing sites to water sources and that their muscle is optimised to deliver a low COT
A muscle biopsy with aponeurosis at each end was removed from the flexor carpi ulnaris muscle of six wildebeest under open aseptic conditions and immediately returned to the field lab by helicopter
Equivalent biopsies were collected from flexor carpi ulnaris of seven adult cows at a UK abattoir

Summary

Introduction

We cycled muscle biopsies at 0.5 Hz at 25oC, which approximated to temperature-corrected wildebeest walking stride frequency (Fig. 1r) and recorded force, length and heat production. For both wildebeest and cow the efficiency of net work production was strongly dependent on stimulation phase and peaked at either -0.1 or 0.0 for all duty cycles (Fig. 3b,f).

Results

Conclusion