Sleep is a highly conserved behavioral state observed universally across the animal kingdom. Its ubiquity suggests that sleep serves critical biological functions maintained throughout evolutionary history. Sleep dimorphism is also widespread across taxa. The crab Neohelice granulata is a very good model for conducting behavioral and physiological experiments. We have recently begun describing its spontaneous activity/rest diel rhythms, defining rest periods, and assessing whether these periods meet the criteria to be considered “sleep.” This initial study revealed clear diel rhythmicity, with two peaks of high activity near dawn and dusk respectively, and a prolonged rest phase during midday and afternoon in males. During this rest phase, males often adopted a characteristic posture, with a flattened carapace, retracted claws, and a preference for staying near corners. Recent studies have also reported notable behavioral differences between males and females of this species in prey capture and escape responses. In this project, we aim to investigate whether sexual dimorphism exists in the activity/rest cycles of adult male and female crabs, and whether these patterns vary with the reproductive cycle. Here, we present preliminary results on the activity/rest patterns of adult males and females during autumn, a non-reproductive period. Our findings suggest that, while the overall activity pattern is conserved, some differences are also evident.