Digging deeper: Species and sex differences in burying beetles during periods of inactivity

Burying beetles, Nicrophorus sp. exhibit strong circadian rhythms and bury into soil when not active.  This study tested burial depth by males and females of three diurnal and two nocturnal species of burying beetles.  In the laboratory, 1.2 meter modified polyvinyl chloride (PVC) tubes containing sandy loam soil were used to assess burial depths during periods of inactivity.  For all diurnal species, females buried to significantly greater depths than males with female N. carolinus burying to 68 ± 8.7 cm (Mean ± 1 SE) compared to males at 36.5 ± 6.14 cm.  Males and females of nocturnally active N. orbicollis and N. americanus buried to similar depths at approximately 20 cm.  The effect of cooling temperatures on beetle depth during periods of inactivity was tested using environmental chambers; however, lowered temperatures did not cause changes in mean burial depths.  The results of this study reveal that burying beetles tunnel into soil during periods of inactivity and suggest that preconstruction activities that only affect soil surfaces should pose little risk to buried beetles in areas where the endangered American burying beetle, N. americanus occur.  The research further reveals an unexpected difference in burial depths by activity pattern and by beetle sex.