Phantom decoys alter perceived missed opportunity costs and increase risky foraging decisions

Foraging decisions about risk and reward are driven by an option’s perceived value relative to foregone alternatives, i.e. missed opportunity costs (MOCs). Information that alters perceptions about alternatives (i.e. perceived MOCs) should therefore influence animal behaviour, yet perceived MOCs are overlooked in wildlife management and rarely manipulated. Phantom decoys are attractive but inaccessible options (i.e. missed opportunities) that change decision-making, seemingly by altering perceptions of MOCs. Using phantom decoys, we conducted two experiments to: a) test if misinformation about MOCs alters risk versus reward foraging decisions; and b) assess whether decoys can increase trapping rates by changing how animals trade off trap danger for rewards inside. Firstly, we conducted a giving-up density (GUD) experiment on wild house mice (Mus musculus) in large natural enclosures, creating patches comprising safe and risky trays of high- and low-quality foods, with decoys at half the patches. Where decoys were present, mice foraged longer in risky trays, accepting greater risk at these patches compared to otherwise identical patches without decoys. Secondly, in a field trapping experiment, we positioned decoys beside trap entrances, and compared capture rates to controls. More mice were captured in traps with decoys outside them. Our results demonstrate how information alone can shape perceptions of MOCs to increase risky behaviour. Behavioural responses to ‘irrelevant’ alternatives (i.e. phantom decoys) have traditionally been considered irrational. Our findings suggest that attractive resources provide valuable information about the environment, even if inaccessible, highlighting the potential for decoy information to alter decision-making to improve wildlife management outcomes.