Water loss rates and desiccation mortality relate to circadian rhythms for two species of burying beetle

During summer months burying beetles (Coleoptera Silphidae) experience high mortality when captured in pitfall traps with dry soil. Among the silphidae, species have different activity patterns and for this study, we compared survival and water loss between the diurnal Nicrophorus carolinus and the nocturnal N. orbicollis at five different temperatures (12, 16, 20, 24, 28 C) at low humidity or with access to water. Mortality from desiccation increased with temperature and was significantly different between species. On average, N. carolinus survived twice as long as N. orbicollis at temperatures above 16 C for those beetles exposed to low humidity without water. At all temperatures, most beetles with access to water survived for the duration of the experiment. The significance of these findings is that burying beetles have relatively high water loss rates leading to mortality from desiccation if they do not have access to water. Moreover, the differences in circadian rhythms match predictions based on desiccation tolerance. These findings further suggest that the federally endangered American burying beetle, Nicrophorus americanus which is nocturnally active like N. orbicollis is also likely to be susceptible to water loss and that its current distribution may be linked environmental moisture.