In this letter, a low-weight and low-power noninvasive ECG heart beat detector for pulse analysis in small vertebrates is proposed and verified on bats. To achieve this low weight, the ECG front end is optimized for low space requirements and low energy consumption, drawing only 30 μA. The complete system, including the system on chip for recording and wireless data transmission, requires 3.3 mA in active mode. Since only a small battery with a weight of 0.6 g is used, this low power consumption is necessary to still be able to reach a continuous measurement time of more than 6 h. Compared to other solutions, this newly proposed system gathers data via noninvasive electrodes while still achieving a high signal quality and, at the same time, is light enough to allow airborne measurements without affecting the animal's behavior.