An energy-aware, collaborative tracking algorithm is pro-posed for ad-hoc wireless sensor networks. The algorithm is implemented distributively by passing sensing and com-putation operations from one sensor to another. In order to maximize the life-time of the network, this active sensor is chosen by a high end sensor in order to minimize the cost function based on the total energy spent by the network at each time instant. Assuming a wireless ad-hoc sensor network in which low end sensors are randomly distributed with data gathering node as a high end sensor, a state-space model for a target motion and sensor measurement and a cost function based on energy requirements for communication and sensing has been derived. Simulation results for ...