Candidate-anchor excursions in mouse open-field recordings: exploratory comparisons across age, wheel exposure and stress

Open-field trajectories contain departures and returns whose geometry is lost in total-distance summaries. We located a candidate anchor from sustained-stop density and measured excursion rate, extent, speed asymmetry and straightness asymmetry in a local pilot of 12 male C57BL/6N mice and 151 public recordings from 121 mice. All anchor-relative primary outcomes had within-contrast corrected q > 0.05. The 12-month group had a shorter-extent estimate in 25/27 parameter settings, while relative return-speed direction varied. After 24-h rotating-wheel exposure, estimates favoured fewer excursions and the straightness-difference estimate shifted upward in 27/27 settings. At 45 min after acute swim, estimates favoured more frequent, shorter excursions, with an imprecise time interaction. Chronic restraint showed a positive excursion-extent direction across the grid. The social-instability extent contrast reversed between 42 cm and 45 cm calibrations because the cm/s stop threshold redefined stops under a changed length scale. Local estimates also depended on boundary handling. These are exploratory, cohort-specific descriptions. Four mice per local condition, unresolved components of wheel exposure and animal-level inference for cage-allocated chronic treatments limit biological interpretation. Replication requires independent detector validation and analysis at the treatment-allocation unit.