Sex- and age-related variations in seasonal and circadian activity of the Nose-horned Viper Vipera ammodytes (Linnaeus, 1758)

The seasonal and circadian activity patterns of Vipera ammodytes were studied in five sites western Bulgaria between 2014 2017. was active from the end February to first half November. In spring, adult males emerged a few weeks earlier than females immature vipers. autumn, different sex/age groups started their hibernation approximately at same time. We registered differences activities groups. Adult subadults mostly encountered during spring juveniles mainly while encounter rate steady throughout period. Females’ varied according reproductive status. observed might be result complex effects many factors, such as climatic conditions, behaviour cost reproduction sexes, well trade-off precise thermoregulation, predation risk foraging needs.