Pheromonally mediated mate attraction by males of the burying beetle Nicrophorus orbicollis: alternative calling tactics conditional on both intrinsic and extrinsic factors

Male burying beetles attract females using a pheromonal signal and can prov ide parental care and a food resource, vertebrate carrion, for their develo ping offspring. But males attempt to attract females even when they have no carrion. We examined the factors that influence male behavior directed tow ard finding or attracting mates in both field-caught and laboratory-reared Nicrophorus orbicollis, a North American burying beetle. We investigated wh ether male behavior differed based on both intrinsic (size) and extrinsic ( resources held) differences among males. Further, we examined repeatability of individual behaviors and the effect of holding or lacking resources on these repeatabilities. Field-caught and laboratory-reared individuals diffe red in overall activity but not in their behavioral repertoire, making stud ies of laboratory-reared males relevant The behavior of individual males wa s very consistent within a condition, but plastic between resource conditio ns. The frequency of calling (adopting a posture that indicates pheromone r elease to am-act females) depended on male size when males did not hold res ources, but this relationship disappeared when males held resources. Withou t carrion, smaller males called more frequently than did larger males. When holding carrion, smaller males reduced their calling, whereas larger males significantly increased the frequency with which they attempted to attract females and reduced the amount of time they spent searching. Thus, calling behavior of males was conditional on not only intrinsic and extrinsic fact ors, but also an interaction between them. We suggest that the changes in c alling represent alternative tactics based on the costs and benefits of att racting both potential mates and competitors, which differ for males of dif ferent sizes.