American Burying Beetle Nicrophorus Americanus Research Articles

Short-term movement patterns of the endangered American burying beetle Nicrophorus americanus

We conducted a mark–recapture study to evaluate short-term movements of the endangered American burying beetle Nicrophorus americanus. We found that beetles moving between sites averaged 1.23 km night −1 in their search for carrion ( n=23 movements between sites) with a range from 0.25 km for 1 night to a maximum of 10.0 km over 6 nights. In support of the supposition that American burying beetles are generalists in their search for carrion, we observed individual beetles moving between different habitat types (71% of recaptures were in a habitat different from that of the previous site of capture), including movements between grassland and woodlands, as well as between bottomland and upland woodlands. No differences in recapture rates were detected between males and females, or between teneral and fully sclerotized beetles. No beetles were recaptured between trapping sessions within a few weeks of one another within the same year, or from 1 year to the next. The relatively long distances that individual beetles move and the potentially short residency time should be taken into account when evaluating data from monitoring of extant populations and when devising plans to establish new ones.

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

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.

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

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.