This video captures a head-restrained mouse in a dark environment, with DeepLabCut (DLC) trained to detect the borders of the pupil. The video is accelerated 5 times to better visualize the dynamic changes. When the laser is on, the pupil becomes clearly visible. Over time, the pupil contracts while whisking activity decreases. Interestingly, when the mouse actively explores its environment, evidenced by whisking behavior, the pupil dilates, reflecting increased arousal or attention. Out-of-focus whiskers occasionally pass in front of the pupil, providing additional context for the mouse’s exploratory behavior. While blinking artifacts are present in the raw video, they will be removed during post-processing to ensure clean data for analysis. This recording demonstrates the intricate relationship between pupil dynamics and whisking activity, offering valuable insights into sensory-motor behavior and arousal in mice. The use of DeepLabCut enables precise, markerless tracking for advanced behavioral analysis.