Habitat selection, breeding success and conservation of the endangered American burying beetle Nicrophorus americanus

Abstract

We tested the hypothesis that the decline of the endangered American burying beetle Nicrophorus americanus resulted primarily from its relatively large size and its specialized breeding requirements (vertebrate carcasses which, after burial, are used to nourish their young). Because it is the largest member of the burying beetle guild, N. americanus requires larger carcasses for breeding (optimal carcass mass is between 100 and 300 g). In comparison to smaller carcasses, larger carcasses are more rare and more difficult to bury. Therefore, while N. americanus may feed in many habitats, its optimal breeding habitats may be limited to those with a substantial litter layer and relatively deep, loose soils. Given this, Anderson (1982 Coleopt. Bull., 36) hypothesized that the decline of N. americanus resulted from deforestation in North America. The results of our regional- and local-scale field studies, and manipulative field experiments, support Anderson's hypothesis. At a regional scale (i.e. across its range in Oklahoma), distributions of N. americanus populations were biased toward forested sites with relatively deep soils (p < 0·001). At a local scale, individual N. americanus exhibited a strong and highly significant (p < 0·001) preference for mature forests over clearcuts. Finally, our breeding experiment with pairs of N. americanus placed on carcasses in either grassland or forested habitats indicated that breeding success of this species was substantially and significantly (p < 0· 05) higher in forested ecosystems.