High water-loss rates and rapid dehydration in the burying beetle, Nicrophorus marginatus

During the summer months, there is a high mortality of burying beetle (Coleoptera: Silphidae) species in pitfall traps containing dry soil. The present study investigated the possibility that the burying beetle Nicrophorus marginatus is highly susceptible to death from desiccation. In the laboratory, adult beetles lose 1-5% body mass per hour in low humidity conditions (25-30% relative humidity), depending on temperature. This rate of water-loss results in a 50% mortality within 7-16 h at temperatures between 16 and 28°C. Nicrophorus marginatus produces oral and anal defensive secretions when disturbed but these secretions do not significantly contribute to the high rate of water loss. Beetles readily drink and thus beetles with access to water or in high humidity conditions suffer near zero mortality. For comparison, the similarly sized mesic bess beetle (Coleoptera: Passalidae), Odontotaenius disjunctus, and a large nocturnal tiger beetle (Coleoptera: Cicindelidae), Amblychila cylindriformis, are exposed to dehydrating conditions. Nicrophorus marginatus have higher rates of water-loss (by 26% and 79%, respectively). It is predicted that the diurnal N. marginatus uses behavioural mechanisms to avoid lethal water loss. In the field, N. marginatus displays a strong bimodal activity pattern, avoiding the hottest hours of the day. The significance of these findings is that N. marginatus defies normal predictions of association between water-loss rates and habitat type, and has extended its range into apparently unfavourable habitats despite high water-loss rates. In addition, the results suggest that researchers should provide moisture when studying burying beetles, including the endangered American burying beetle (Nicrophorus americanus).