Data collection at the sink node from the surrounding sensor nodes is an important step in most of the wireless sensor network (WSN) applications. Most of existing data gathering protocols work well only when the sensor nodes are relatively immobile. In this paper, we propose an energy efficient data collection protocol, referred to as low-energy dynamic cluster selection (LEDCS), for gathering data from mobile nodes. We introduce a dynamic cluster structure so that when a node has data to transmit for the sink, it is able to join the nearest cluster-head. We provide analytical results on the delay characteristics of the proposed protocol and compare the simulations results with two recently proposed protocols: LEACH-IR and CM-IR. We show that when the nodes are mobile, with the increase in the velocity of sensor nodes the total amount of data received by the sink in LEDCS is up to 80% and 52% higher than LEACH-IR and CM-IR, respectively, assuming the same energy budget at each node in all the protocols.