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Enhanced Tracking System Based on Micro Inertial Measurements Unit to Measure Sensorimotor Responses in Pigeons

The ability to orientate and navigate is critically important for the survival of all migratory birds and other animals. Progress in understanding the mechanisms underlying these capabilities and, in particular, the importance of sensitivity to the Earth's magnetic field has, thus far, been constrained by the limited number of techniques available for the analysis of often complex behavioral responses. Methods used to track the movements of animals, such as birds, have varied depending on the degree of accuracy required. Most conventional approaches involve the use of a camera for recording and then measuring an animal's head movements in response to a variety of external stimuli, such as changes in magnetic fields. However, video tracking analysis (VTA) will generally provide only a 2D tracking of head angle. Moreover, such a video analysis can only provide information about movements when the head is in view of the camera. In order to overcome these limitations, the novel invention reported here utilizes a lightweight (<;10 g) inertial measurement unit (IMU), positioned on the head of a homing pigeon, which contains a sensor with tri-axial orthogonal accelerometers, gyroscopes, and magnetometers. This highly compact (20.3 × 12.7 × 3 mm) system can be programmed and calibrated to provide measurements of the three rotational angles (roll, pitch, and yaw) simultaneously, eliminating any drift, i.e., the movement of the pigeon's head is determined by detecting and estimating the directions of motion at all angles (even those outside the defined areas of tracking). Using an existing VTA approach as a baseline for comparison, it is demonstrated that the IMU technology can comprehensively track a pigeon's normal head movements with greater precision and in all three axes.