Prosocial behaviour is common and aggressive behaviour rare in free-living, brown rats in camera trap material

Abstract While brown rats ( Rattus norvegicus ) are a widely used model species in behavioural studies, not much is known about their behavioural patterns in the wild, despite such populations being common and widespread across the globe. Nevertheless, widely used camera traps can provide much-needed material on the behaviour of not only rats but also many other synanthropic species. To understand rat social behaviour and assess the potential of opportunistically sourced video material, we constructed ethograms and analysed rat behaviour on a site where a colony of rats were supplementally fed to collect material for an art project. Across the nine-month observation period and approximately 2,000 h of video material, we found 222 video clips with more than one rat individual present simultaneously. These clips contained neutral and agonistic behaviours (such as stealing food and chasing), but also affiliative behaviours (smelling and nose touching) and even prosociality (such as play and peaceful sharing of food). Associative behaviour was more common whereas agonistic behaviour was rare. Our results show that even opportunistically collected video material can be used for ethological analysis and can reveal new aspects regarding the behaviour of poorly studied species or contexts.