Multiple captures as indicator of social tolerance in a guild of terrestrial rodents

Abstract

Information on intra- and inter-specific social tolerance is useful to evaluate the role of social interactions at shaping population dynamics. This is particularly interesting for sympatric species with similar ecological requirements that can be potential competitors. In this light, we investigated multiple captures of Apodemus flavicollis, A. sylvaticus and Myodes glareolus constituting a guild of forest- and ground-dwelling rodents in central Italy. Small mammals were live-trapped every other month for four years. Multiple captures made up 3% of total captures, with a very similar occurrence in all three species. In each species the number of multiple captures increased with both population density and amount of caught conspecifics. Individuals of the same species were caught together in 85% of multiple captures. In all three species, sexually active individuals were also involved in homosexual and interspecific multiple captures, suggesting that multiple captures are not primarily caused by reproductive behaviour. The occurrence of intra- and inter-specific captures and the absence of injury signs in individuals trapped together suggest social tolerance and support the hypothesis of weak competitive interactions between these species constituting a guild of rodents in this sub-Mediterranean deciduous oak forest. As multiple capture events can occur during live trapping, we stress the importance of utilising this secondary data to gain useful information on social factors influencing small mammal populations.