Physiology and the future of animals in shifting-sand deserts: living, moving and thermoregulating in the sand.

The conservation of the animals of the shifting-sand deserts requires a thorough understanding of the physiological mechanisms that not only enable them to function in the desert, but also may buffer them against future change. The animals there contend with little water and poor food resources. The animals of shifting-sand deserts also must move on and in loose sand and cannot construct unsupported burrows. Most are invertebrates, but the deserts also are home to many vertebrate species, mainly lizards. We describe the biomechanics of their locomotion on and in the sand. Some are quiescent buriers that remain near the surface, but remarkably, small desert mammals can swim to depths of more than 500 mm. Diurnally active animals retreat into the sand beneath their feet to avoid overheating in summer and freezing in winter, but burial and emergence are not determined by selection of the best thermal or hygric environment. We address the conundrum of why so many species that are active in the sun are black. The sand provides a fortress that resists invasion, but from which the residents cannot escape. The animals are under threat from climate change and from human use and abuse of the shifting-sand deserts, even though the sand is unsuitable for concrete. We argue that efforts to combat desertification do not absolve us from a need to conserve shifting-sand deserts. In a companion review, we discuss how the physiology of breathing, the acquisition of metabolic energy and the management of body water impacts the conservation of the animals of shifting-sand deserts.