Ecological constraints on mammalian sleep architecture
Preston, B; Nunn, C; McNamara, P; Barton, R; Capellini, Isabella
Isabella Capellini I.Capellini@hull.ac.uk
In this chapter, we review the evidence for how ecological factors, including predation risk and foraging requirements, might shape patterns of sleep among mammals. We also highlight the need for more research on the degree to which animals can exhibit flexibility in their sleep requirements, as such plasticity could provide a means to overcome constraints, particularly when the costs associated with sleep vary on daily or seasonal time scales. We begin by discussing if the available data are informative and appropriate for studying the role of ecology in the evolution of sleep architecture. We then move on to review how different characteristics of sleep have evolved alongside one another, as these traits form the foundation for our discussion of ecological constraints that follows. We restrict our discussion to terrestrial mammals and exclude monotremes, such as the platypus (Ornithorhynchus anatinus) and echidna. Aquatic mammals, in fact, exhibit a different sleep architecture, and it is still uncertain whether monotremes possess two distinct sleep states—rapid-eye-movement (REM) and non-REM (NREM) sleep—as is observed in most other mammals. We note, however, that the dramatic differences in sleep characteristics of terrestrial and aquatic mammals provide evidence for the claim that ecology influences sleep architecture. In aquatic environments, mammals appear to forego REM sleep—or at least REM indices are truncated in aquatic species relative to the range of values seen in terrestrial species—and unihemispheric NREM sleep is found. Some authors argue that the evolution of unihemispheric sleep and suppression of REM sleep, with its associated paralysis, allows cetaceans and eared seals to maintain the motor activity necessary to surface and breathe, while others suggest unihemispheric sleep might facilitate predator detection or help balance heat loss to the water by constantly swimming.
|Publication Date||Jan 1, 2012|
|Book Title||Evolution of Sleep. Phylogenetic and functional perspectives|
|APA6 Citation||Preston, B., Nunn, C., McNamara, P., Barton, R., & Capellini, I. (2012). Ecological constraints on mammalian sleep architecture. Evolution of Sleep. Phylogenetic and functional perspectives, 12389. Cambridge University Press|