Understanding rogue behaviour provides insight for limiting damage by a global bird predator

Some individuals within a predator population inflict disproportionate impacts on prey. Managing this ‘rogue’ behaviour is crucial when prey is of conservation concern, but challenging when its prevalence is unknown. We ran a multi-stage experiment to discover the prevalence of ‘rogue’ predatory behaviour within an invasive black rat Rattus rattus population and if exposure to unrewarding prey odour inhibited interest in prey. First, marked rats were exposed to quail eggs to identify ‘rogues’ (individuals that ate eggs on multiple nights). We then tested if rats remained motivated to hunt eggs after approximately 14 days exposure to an unrewarding bird odour. From 85 marked rats, 19 were ‘rogues’ and showed no demographic differences to the rest of the population. However, ‘rogues’ visited the unrewarded odour for more nights and were more likely to hunt eggs after exposure to prey odour. Our results suggest that ‘rogues’ are behaviourally, not demographically, different. Problematic behaviour is likely facilitated by reinforcement and experience. Their interest in unrewarding prey odours suggests ‘rogues’ are highly motivated and attentive to prey cues. Complex spatial and temporal exposure to unrewarded cues (misinformation) may deter interest in prey by ‘rogues’ but remains to be tested. • Rat control can be ineffective at reducing predation on birds because 'rogue' individuals that do damage are not targeted. • Highly motivated rogues are behaviourally, not demographically different, and can be a small proportion of the population. • Undermining predator motivation with habituation to prey cues may target rogue individuals better than traditional techniques.