【動物学】ヌーが遠くまで移動できるのは効率的に働く筋肉のおかげ

Efficient muscle fibres allow wildebeest to travel long distances without overheating, reports a paper published online this week in Nature. These findings represent the first direct energetic measurements of muscle fibres of large mammals, and suggest how animals living in desert environments can cope with seasonal and local variations in rainfall, food, and climate.

An animal’s capacity for long-distance travel is dependent on their energy utilization and heat production when moving. Large animals are more efficient at travelling large distances overland than smaller species, but the efficiency of individual muscle fibres is less understood. In mice, it is known that a third of the energy is translated into movement while the other two-thirds are expended as heat. The direct study of living muscle fibres is difficult, even for small animals, and it hasn’t been attempted for anything larger than a rabbit.

Alan Wilson and colleagues have now studied the efficiency of muscle fibres for the migrating wildebeest. The authors used GPS tracking collars with movement and environmental sensors to show that blue wildebeest living in a hot arid environment in Northern Botswana could travel up to 80km over five days without drinking. They report that wildebeest muscle fibres convert two thirds of energy into work, and waste only a third as heat — substantially more efficient than both comparably sized animals such as cows and small animals such as rabbits. This muscle efficiency minimizes heat produced by the wildebeest, which suggests that they lose less water through frequent exhaling and so need to drink less frequently.