Social ad-hoc networks can be composed of a large number of tiny, wireless, battery-powered nodes, and exhibit arbitrary mobility. We aim to enable the execution of distributed applications that depend on capturing network dynamics across large-scale social ad-hoc networks. Conservation of the nodes' fixed energy budget is the chief concern in all design decisions, and necessitates that wireless communication is kept to a minimum. In this paper we present GMAC1 : a gossiping TOMA MAC layer created to address these problems. We analyze its efficiency in achieving and maintaining a tight network-layer synchronization with respect to the active periods of node radios.