Daily activity patterns and response to lunar cycle of Chinchilla chinchilla and Lycalopex culpaeus in an extreme Andean environment: insights into the predator-prey relationship

Circadian rhythms, which reflect 24-hour activity cycles, are critical for survival, helping species optimize foraging and predator avoidance. In principle, prey species are expected to adjust their activity patterns to minimize the overlap of their foraging activities with that of predators, while predators may align their activity patterns with that of their prey. In this study, the daily activity and response to the lunar cycle of two native Chilean mammals, the endangered short-tailed chinchilla ( Chinchilla chinchilla ) and one of its predators, the culpeo fox ( Lycalopex culpaeus ), were studied in a 4500 m-elevation area in northern Chile during three consecutive years using trap cameras. While chinchillas presented a predominantly nocturnal activity pattern, foxes were more active during the day, resulting in a low temporal overlap in their activity patterns. Regarding the response to the lunar cycle, the short-tailed chinchilla rhythm remained relatively constant across lunar phases, and the culpeo fox showed increased activity during the first and third lunar quarters at intermediate luminosity. The activity pattern shown by the two species differed from the expected under a predator-prey relationship. We suggest that the availability of alternative diurnal prey may provide greater benefits to L. culpaeus than to the endangered C. chinchilla , potentially shaping their daily activity rhythms and responses to the lunar cycle.