Camus: a video-based framework for continuous behavioral monitoring in the mouse home-cage

Abstract

Home-cage activity is a window into the spontaneous behavioral repertoire of mice. These behaviors are organized across the circadian cycle, and disruptions in their duration, frequency, or organization may provide sensitive measures of neurological or psychiatric dysfunction. While continuous monitoring can help track the dynamics of spontaneous behavior, video recording in conventional laboratory cages is limited by compact cage geometry, opaque cage tops, and obstructed views of animals, food, and water. We therefore developed Camus, a Camera for home-cage recordings of Mus musculus mice. Camus integrates off-the-shelf USB cameras with infrared illumination and custom 3D-printed components for access to food and water without obstructed views. The modular design pairs continuous video acquisition with a manually validated computer-vision model to quantify locomotion, feeding, drinking, and nesting-related behavior across multiday recordings. A single desktop computer can record as many as 20 cages in parallel at an incremental cost of approximately $250 per cage, recording more than 99% of expected frames at 640x360-pixel resolution and 30 frames per second. Camus captured circadian structure in locomotion, feeding, and drinking. Camus also captured nest-building and sex-specific differences in nest dynamics. Using Camus with transgenic 5xFAD mice overexpressing amyloid revealed selective, age-progressive deficits in nesting behavior. Camus provides a scalable, open-source platform that combines accessible hardware, automated video monitoring, and machine-learning based analysis for continuous and potentially longitudinal behavioral phenotyping.