Seasonal circadian rhythm shift and lunar chronobiology of the nine-banded armadillo (Dasypus novemcinctus)

Abstract

Abstract Nine-banded armadillos (Dasypus novemcinctus) are nocturnal, semifossorial, insectivorous mammals that historically live in warm climates but have been moving northward over the past 150+ y. As armadillos move into more-temperate climates, behavioral adjustments occur in response to decreasing temperatures. Observations in northern latitudes have noted more activity during the daytime in the winter, indicating a shift in circadian rhythm. Such behavioral plasticity may allow individuals to forage when temperatures are optimal for thermoregulation. We recorded armadillo activity for 6 mo using game cameras. We created nocturnal, crepuscular, and diurnal activity indices and then plotted them as a function of time. We compared temperatures of when armadillos were photographed to temperatures when other animals were photographed. Analyses suggest that a seasonal shift in circadian rhythm does occur and that air temperature is an important factor. Although armadillos have previously been reported to ...