Day and night in the subterranean: measuring daily activity patterns of subterranean rodents (Ctenomys aff. knighti) using bio-logging.

Milene G Jannetti,Gisele A Oda,C Loren Buck,Veronica S Valentinuzzi

doi:10.1093/conphys/coz044

Milene G Jannetti, Gisele A Oda + Show 2 more

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https://doi.org/10.1093/conphys/coz044

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Abstract

While most studies of the impacts of climate change have investigated shifts in the spatial distribution of organisms, temporal shifts in the time of activity is another important adjustment made by animals in a changing world. Due to the importance of light and temperature cycles in shaping activity patterns, studies of activity patterns of organisms that inhabit extreme environments with respect to the 24-hour cyclicity of Earth have the potential to provide important insights into the interrelationships among abiotic variables, behaviour and physiology. Our previous laboratory studies with Argentinean tuco-tucos from the Monte desert (Ctenomys aff. knighti) show that these subterranean rodents display circadian activity/rest rhythms that can be synchronized by artificial light/dark cycles. Direct observations indicate that tuco-tucos emerge mainly for foraging and for removal of soil from their burrows. Here we used bio-logging devices for individual, long-term recording of daily activity/rest (accelerometry) and time on surface (light-loggers) of six tuco-tucos maintained in outdoor semi-natural enclosures. Environmental variables were measured simultaneously. Activity bouts were detected both during day and night but 77% of the highest values happened during the daytime and 47% of them coincided with time on surface. Statistical analyses indicate time of day and temperature as the main environmental factors modulating time on surface. In this context, the total duration that these subterranean animals spent on surface was high during the winter, averaging 3h per day and time on surface occurred when underground temperature was lowest. Finally, transport of these animals to the indoor laboratory and subsequent assessment of their activity rhythms under constant darkness revealed a switch in the timing of activity. Plasticity of activity timing is not uncommon among desert rodents and may be adaptive in changing environments, such as the desert where this species lives.

Highlights

Massive changes in climate patterns can compromise organismal fitness and population persistence of many species
While most studies of the impacts of climate change have investigated shifts in the spatial distribution of organisms (Root, 1988; Root et al, 2003; Sinervo et al, 2010), shifts in seasonal phenology (Chevin et al, 2010; Lane et al, 2012; Shen et al, 2015; Williams et al, 2017) or daily timing of activity are other important adjustments that can be made by animals in a changing world (Daan, 1981; Halle and Stenseth, 2000; Kronfeld-Schor and Dayan, 2003; Levy et al, 2018)
Due to the importance of light and ambient temperature cycles in shaping activity patterns, it is interesting to study their effects on organisms that inhabit extreme environments with respect to the 24-hour cyclicity of Earth

Summary

Introduction

Massive changes in climate patterns can compromise organismal fitness and population persistence of many species. The light/dark cycle of Earth imposes a fundamental 24hour pace that structures the timing of biological activity. In mammals, this is achieved by light/dark entrainment of endogenous, hypothalamic circadian clocks, resulting in rhythmic, 24-hour activity/rest alternations (Rusak, 1982). This is achieved by light/dark entrainment of endogenous, hypothalamic circadian clocks, resulting in rhythmic, 24-hour activity/rest alternations (Rusak, 1982) This endogenously generated rhythm can be profoundly altered by environmental cues, a phenomenon known as ‘masking’ (Aschoff et al, 1982). Due to the importance of light and ambient temperature cycles in shaping activity patterns, it is interesting to study their effects on organisms that inhabit extreme environments with respect to the 24-hour cyclicity of Earth. The subterranean environment offers an opportunity for these studies, due to the constant darkness and attenuated temperature cycles of the burrow environment, characteristics thought to diminish the selective pressure of keeping daily activity patterns (Beale et al, 2016)

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