@article {70379, title = {Whole-body 3D kinematics of freely behaving Drosophila}, journal = {bioRxiv}, year = {2026}, month = {2026 May 04}, abstract = {

Understanding how nervous systems generate coordinated movement requires precise measurement of body kinematics during natural behavior. The fruit fly, Drosophila, is a model organism with sophisticated behavior and well-studied neural circuits, but tracking fly movements in 3D remains challenging because of their teeny bodies, rapid movements, and frequent self-occlusions. Here we present a pipeline for markerless, full-body 3D pose estimation of fly terrestrial behavior, combining seven synchronized high-speed cameras to capture whole-body kinematics at 800 frames per second. We trained a hybrid 2D/3D deep learning model to track 50 keypoints, then refined them to produce anatomically feasible kinematic trajectories through a retargeting process that solved an inverse kinematics problem constrained by a biomechanical body model. Analysis of 3D kinematics revealed that flies perform grounded running across their full speed range, without transitioning between discrete gaits. Using multi-animal tracking, we found that courting males coordinate both wings during song and modulate body pitch to track the female{\textquoteright}s vertical position. Our open-source pipeline and 3D kinematic dataset of fly behavior provide a foundation for neuromechanical modeling and mechanistic studies of motor control in a genetically tractable model organism.

}, doi = {10.64898/2026.05.03.722293}, url = {https://www.biorxiv.org/content/early/2026/05/04/2026.05.03.722293}, author = {Ispizua, Juan I. and Abe, Elliott T. T. and Yan, Jinyao and Othayoth, Ratan and Sawtelle, Steven and Atkins, Felisha and Shiozaki, Hiroshi and Meier, Niko R. and Wong, Jovanka and Tran, Tiffany T. and Mori, Catherine K. and Voigts, Jakob and Stern, David L. and Brunton, Bingni W. and Tuthill, John C. and Johnson, Robert Evan} }