GENERAL INFORMATION 1. Paper Citation Parker et al. (2026). Phantom decoys alter perceived missed opportunity costs and increase risky foraging decisions. Behavioral Ecology. 2. Brief abstract 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. 3. Originators Finn C. G. Parker, Catherine J. Price, Jenna P. Bytheway, Clare McArthur, Peter B. Banks 4. Contact information Finn C. G. Parker, finn.parker@sydney.edu.au 5. Date of data collection April/May, 2022 & April/May 2023 6. Geographic location(s) of data collection Walpeup, Victoria, Australia 7. Information about funding sources that supported the collection and curation of the data FCGP acknowledges funding from the AW Howard Memorial Trust and the Ecological Society of Australia. PBB acknowledges funding from the Australian Research Council (DP200103148). CJP acknowledges funding from the Australian Research Council (DE220101316). PBB & CM acknowledge funding from the Australian Research Council (DP190101441). ACCESS INFORMATION 1. Licenses/restrictions placed on the data Creative Commons Attribution 4.0 2. Data derived from other sources NA DATA FILES AND VARIABLES 1. foraging_experiment_data.csv Contains giving-up density data collected in experiment number 1 (foraging experiment) of the associated paper by Parker et al. (2026) - ID: Unique identifier for the particular food tray the giving-up density (GUD) was recorded in. The ID contains the treatment (C = control, D = decoy), the enclosure number (1-9), the patch number (1-4), the risk level (r = risky, s = safe), and the food type (barley = b, sunflower = s). - date: The date on which the GUD measurement was taken (DD/MM/YYYY). - night: Giving-up density data was collected over multiple nights. This variable refers to the night on which the relevant GUD measurement was taken. - enclosure: The enclosure in which the GUD measurement was taken (n=9). - treatment: The treatment allocated to the enclosure when the GUD measurement was taken. Decoy enclosures contained phantom decoys at half of the foraging patches. Control enclosures contained no decoys at any patch. - patch: The patch or foraging station that the tray was located in. There were four patches per enclosure, each containing four trays. - risk: The risk level of the tray. Trays were either positioned in vegetation cover (safe), or positioned in the open away from vegetation cover (risky). - food: The food contained in the tray. Trays contained either 20 high-quality food items (sunflower kernels) or 20 low-quality food items (barley grains). - decoy: Indicates whether the tray or patch had a phantom decoy positioned beside it (N = no, Y = yes). - GUD: The giving-up density (GUD), which indicates the number of food items remaining in the tray in the morning. Each tray had 20 food items at the start of each night. 2. field_trapping_data.csv Contains trapping data collected in experiment number 2 (field trapping experiment) of the associated paper by Parker et al. (2026) - year: The trapping session that data was recorded. - grid: The trapping block that the trap was located in. Traps were arranged in spatial blocks to account for patchiness of mouse populations. - row: The row of the grid that the trap was located. - column: The column of the grid that the trap was located. - id: A unique identifier that combines the grid, row, and column that the trap was located. - treatment: The phantom decoy treatment that was allocated to the trap. Phantom Decoy (PD) was an Elliott trap baited with wheat with a phantom decoy located outside immediately beside the trap entrance. Phantom in Trap (PIT) was an Elliott trap baited with wheat with a phantom decoy inside the trap. Wheat (W) was an Elliott trap baited with wheat. - camera: Binary variable referring to whether a camera was present at the trap (1 = yes, 2 = no). Camera data was not used in the field trapping experiment. - night: The night of the experiment that the data was recorded. - visits: The number of visits to a trap recorded by a camera during the night. New visits were classified as any visit > 5 minutes after the previous visit. Camera data was not used in the field trapping experiment. - capture: Binary outcome variable referring to whether a mouse was captured in the trap on that night (1 = yes, 2 = no). In some cases, two mice were caught in the trap on the same night. Those rows have been duplicated. - recapture: Binary outcome variable referring to whether a mouse was recaptured in the trap on that night (1 = yes, 2 = no). Recaptures were determined my shave marks from previous nights. CODE SCRIPTS AND WORKFLOW No analysis scripts are included in this repository. Statistical analyses are fully described in the associated publication and were conducted in R version 4.4.1. R packages used in statistical analyses: - 'glmmTMB' (version 1.1.9) - 'DHARMa' (version 0.4.6) - 'emmeans' (version 1.10.3) - 'lme4' (version 1.1.35.5) - 'boot' (version 1.3.30) - 'ggplot2' (version 3.5.1)