An animal tracking system comprising an implantable device 10 and an external charging device 20. The implantable device 10 can be embedded under the skin of an animal or pet such as a cat or dog and comprises a location module adapted to detect its location and generate an output signal. A radio transmitter 14 transmits the location signal, and a rechargeable power source 17 provides power to the location module and radio transmitter. The location module may use a GPS and/or a GLONASS receiver 15. The rechargeable power source 17 is coupled to a first inductive charging coil 19, and the external charging device 20 comprises a power source 22 and a second inductive charging coil 24 for electromagnetic coupling with the first coil 19. The radio transmitter 14 may form part of a cellular radio and the device may further comprise a Bluetooth (RTM) or Wi-Fi (RTM) module 16 for communication to a remote device,
