[Show abstract][Hide abstract] ABSTRACT: Circadian patterns of activity have important implications for numerous aspects of a species' biology, including patterns of sociality and paternal care. The activity patterns of subterranean rodents are of particular interest because of the presumed lack of environmental entrainment cues available in underground habitats. We used radiotelemetry to monitor activity of adult cururos (Spalacopus cyanus) in 2 populations of this species from north-central Chile. The locations of radiocollared animals from Parque Nacional Fray Jorge (n ¼ 10 adults) and Santuario de la Naturaleza Yerba Loca (n ¼ 8 adults) were determined hourly for 72 consecutive hours during austral summer, 2003. Examination of these data revealed that surface and subterranean activity were largely restricted to daylight hours. Specifically, the following measures of activity were found to be significantly greater during daytime: percentage of animals outside of nest, distance from nest, and distance between successive locations at which an animal was detected. In addition, the occurrence of cururo vocalizations (typically given by animals at burrow entrances) was significantly associated with daylight. Collectively, these analyses indicate that, contrary to the behavior of captive S. cyanus, free-living cururos are diurnal. Physical and social environments in which captive animals are housed may contribute to observed differences in activity between field and laboratory populations of this species.
Journal of Mammalogy - J MAMMAL. 01/2005; 86(2):302-308.
[Show abstract][Hide abstract] ABSTRACT: Circadian rhythms are ubiquitous in many organisms. Animals that are forced to be active around the clock typically show reduced performance, health and survival. Nevertheless, we review evidence of animals showing prolonged intervals of activity with attenuated or nil overt circadian rhythms and no apparent ill effects. We show that around-the-clock and ultradian activity patterns are more common than is generally appreciated, particularly in herbivores, in animals inhabiting polar regions and habitats with constant physical environments, in animals during specific life-history stages (such as migration or reproduction), and in highly social animals. The underlying mechanisms are diverse, but studies suggest that some circadian pacemakers continue to measure time in animals active around the clock. The prevalence of around-the-clock activity in diverse animals and habitats, and an apparent diversity of underlying mechanisms, are consistent with convergent evolution. We suggest that the basic organizational principles of the circadian system and its complexity encompass the potential for chronobiological plasticity. There may be trade-offs between benefits of persistent daily rhythms versus plasticity, which for reasons still poorly understood make overt daily arrhythmicity functionally adaptive only in selected habitats and for selected lifestyles.
Proceedings of the Royal Society B: Biological Sciences 06/2013; 280(1765):20130019. · 5.68 Impact Factor
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