Super-Cooling Point and Effects of Temperature, Moisture, and Habitat on Overwintering Survival of the Threatened American Burying Beetle Nicrophorus americanus.

Most species within the genus Nicrophorus (Staphylinidae: Silphinae: Necrophorini) overwinter as adults during cold months. However, species that were once widely distributed, such as the American burying beetle, Nicrophorus americanus Olivier, experience different overwintering conditions, altered by increasing climate variability, making cold periods less predictable. In this study, we determined the mean super-cooling point of Oklahoma N. americanus to be -1.98 °C, a value that suggests that beetles rely on behavioral avoidance of freezing soils rather than on physiological freeze tolerance or super-cooling. We conducted a series of field experiments in Oklahoma to test the effects of habitat and burial depth on the overwintering survival of N. americanus. Correlations were found between burial depth and the survival of beetles. Highly fluctuating winter temperatures and periods without precipitation increased mortality rates, with adults emerging from overwintering much earlier than previously documented. As climates become warmer and more variable, with temperature fluctuations and altered precipitation patterns, populations of the federally designated threatened N. americanus are at risk of extirpation.