The ZebraNet system includes custom tracking collars (nodes) carried by animals under study across a large, wild area; the collars operate as a peer-to-peer network to deliver logged data back to researchers. The collars include global positioning system (GPS), Flash memory, wireless transceivers, and a small CPU; essentially each node is a small, wireless, computing device. Since there is no cellular service or broadcast communication covering the region where animals are studied, ad hoc, peer-to-peer routing is needed.  Overall, our goal is to use the least energy, storage, and other resources necessary to maintain a reliable system with a very high 'data homing' success rate.  We have built custom hardware platforms and modular software platforms to support these goals. In January 2004, we deployed an 8-node ZebraNet system at the Sweetwaters Game Reserve in central Kenya, and we plan to return in 2005 with a larger system.  More broadly, we believe that the domain-centric protocols and energy tradeoffs studied for ZebraNet will have general applicability in other wireless and sensor applications.