This paper presents the results of a study on the effects of data aggregation for multi-target tracking in wireless sensor networks. Wireless sensor networks are normally limited in communication bandwidth. The nodes implementing the wireless sensor network are themselves limited in computing power and usually have a limited battery life. These observations are recognized and combined to come to efficient target tracking approaches. The main question to be answered is how to accurately track multiple targets crossing an area observed by a wireless sensor network, while limiting the amount of network traffic. Limiting the amount of network traffic reduces the required bandwidth and reduces the required energy. Various computing power aware data aggregation strategies are researched. They have been tested in a simulation environment and compared with each other. The results of the simulations clearly show the benefit of the new data aggregation strategies in terms of energy consumption a...