Diel activity patterns of South Scandinavian high mountain ground beetles (Coleoptera, Carabidae)

Fourteen species of carabids were studied throughout the snowfree season in outdoor arenas above the timberline at Finse, South Norway (60°36′N, 7°30′E). Ten species were nocturnal. Onset of nocturnal activity occurred after termination of twilight with peak activity before midnight, but in June, with less than 1 h of darkness, activity was extended into evening twilight, the peak being around midnight. Linear regressions between ground surface temperature and nocturnal activity predicted zero activity in the range −2.0 to0.8°C, mean −0.5°C, indicating that activity is possible on most nights throughout the snowfree season. Two diurnal species had activity threshold temperatures at 4 and 8°C, respectively, the former with a peak at 16°C and an upper threshold at 28°C. The proportion of nocturnal species in the study area was significantly greater than in lowland open fields. Large and common species were mainly nocturnal, while small and rare species were mainly diurnal. It is suggested that nocturnalism in the South Scandinavian high mountains is a response to avoid bird predation and desiccation.