Probability of Intra- and Interspecific Encounters, and the Duration of Parental Care in Nicrophorus investigator (Coleoptera: Silphidae)

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Abstract
In burying beetles (Nicrophorus), male and female pairs bury small carcasses to supply their larvae with food. Both parents care for their larvae for several days and defend them against other burying beetles that try to usurp the carcass. Male defense is very effective in preventing take-overs by conspecifics, but ineffective against attacks by larger congeners. From information on four species of Nicrophorus, Scott (1998) suggested that this asymmetry affects the duration of male care; males care longer when the major competitors are conspecifics, and leave early if they are larger congeners. We performed a field study examining the phenology of N. investigator Zetterstedt and its sympatric congeners in Bielefeld, Germany. Because of its relatively low abundance, an N. investigator arriving at a carcass had a much higher chance to meet an individual of another species of burying beetle than to meet a conspecific, suggesting that intraspecific competition is less important than competition by congeners. Breeding experiments showed that male care in N. investigator was shorter than in the numerically dominant species N. vespilloides Herbst and N. vespillo (L.), supporting Scott' hypothesis. However, we cannot exclude that the differences in male care were caused by other factors that vary between species, as for example the speed of larval development. Also, the probability of encounter used to estimate the relative importance of intra- and interspecific conflicts only gives a rough estimate of the competitive situation because of differences in fighting ability between species.