Temporal Dissociation Between Activity and Body Temperature Rhythms of a Subterranean Rodent ( Ctenomys famosus ) in Field Enclosures

Abstract

Several wild rodents, such as the subterranean tuco-tucos (Ctenomys famosus),switch their time of activity from diurnal to nocturnal when they are transferred fromfield to the laboratory. Nevertheless, in most studies, different methods to measure activityin each of these conditions were used, which raised the question of whether thedetected change in activity timing could be an artifact. Because locomotor activity andbody temperature (Tb) rhythms in rodents are tightly synchronized and because abdominalTb loggers can provide continuous measurements across field and laboratory, wemonitored Tb as a proxy of activity in tuco-tucos transferred from a semi-field enclosureto constant lab conditions. In the first stage of this study (“Tb-only group,” 2012-2016),we verified high incidence (55%, n = 20) of arrhythmicity, with no consistent diurnal Tbrhythms in tuco-tucos maintained under semi-field conditions. Because these resultswere discrepant from subsequent findings using miniature accelerometers (portableactivity loggers), which showed diurnal activity patterns in natural conditions (n = 10,“Activity-only group,” 2016-2017), we also investigated, in the present study, whether thetight association between activity and Tb would be sustained outside the lab. To verifythis, we measured activity and Tb simultaneously across laboratory and semi-fielddeploying both accelerometers and Tb loggers to each animal. These measurements(n = 11, “Tb + activity group,” 2019-2022) confirmed diurnality of locomotor activity andrevealed an unexpected loosening of the temporal association between Tb and activityrhythms in the field enclosures, which is otherwise robustly tight in the laboratory.