Relationship between numbers of the endangered American burying beetle Nicrophorus americanus Olivier (Coleoptera : Silphidae) and available food resources

Abstract

The American burying beetle Nicrophorus americanus Oliver (Coleoptera : Silphidae), designated in the United States as an endangered species, requires vertebrate carcasses for feeding, breeding and rearing young (optimally 80–200 g for breeding, but beetles readily feed on smaller carcasses). Previous studies at the 29 000 ha Fort Chaffee Military Reservation, Arkansas and the 20 000 ha Camp Gruber Training Site, Oklahoma have shown that with habitat defined based on vegetation, the species is a habitat generalist when feeding. Given that the species was not selective relative to habitat type at Fort Chaffee, we investigated whether there was a relationship between numbers of beetles and measures of vertebrate abundance. For beetles, eight baited pitfall traps were set for three nights in 1992 and 1993 along each of the 52 transects where, in previous years, birds and mammals had been censused. Birds were counted using a modified point-count technique (five counts during May–June 1989–1991), and mammals were sampled with ‘museum special’ snap traps and rat traps (three two-day traping periods during May–June 1989–1991). In analyzing 0–200 g mammals trapped and birds counted on the transects, significant correlations were found of the number of American burying beetles caught with biomass of mammals; biomass of mammals plus birds; numbers of species of mammals; and numbers of individual mammals. American burying beetles frequented sites where small vertebrates (particularly mammals) were relatively abundant, irrespective of the predominant habitat at that site.