Moving the corpse to hide the evidence: horizontal as well as vertical movement is important when burying beetles cache a carcass

Abstract

Being the first to discover a resource can provide a competitive advantage (priority effect), even for an animal that is inferior in aggressive contests. Nicrophorus spp. (burying beetles) are known for caching a small vertebrate carcass as provision for their young, reducing volatile cues available to rivals by burying the carcass (vertical movement) and by altering the microbial community. A decomposing carcass, however, can leave cues (residues of decay) on soil and leaf litter that a burying beetle has less opportunity to neutralize. I investigated whether horizontal movement of the carcass by burying beetles, separating the carcass from soil at the site of death, might reduce competition from congeners. When fresh carcasses were placed in the field on top of soil with residues of decay, akin to no horizontal displacement, carcasses were discovered within 24 h by free-flying competitors more frequently (58.2%) than when the carcass was placed 1 m from treated soil (8.3%). In a second experiment, carcasses were more likely to be discovered by burying beetles when a chemical attractant (methyl thiocyanate) was placed near a carcass (0.03 and 0.25 m) than when it was placed more distant (1 and 5 m) or for controls (no attractant). The results suggest that horizontal displacement of a carcass after discovery serves not only to locate a suitable spot for burial but also to reduce information available to rivals searching for the resource.