1. Desert Ecology Research Group, School of Life and Environmental Sciences; University of Sydney; NSW 2006 Australia
2. Wildlife Conservation Research Unit, Department of Zoology; University of Oxford; The Recanati-Kaplan Centre, Tubney House Tubney Abingdon OX13 5QL U.K.
3. Global Trophic Cascades Program, Department of Forest Ecosystems and Society; Oregon State University; Corvallis OR 97331 U.S.A.
4. Centre for Integrative Ecology, School of Life and Environmental Sciences; Deakin University; Burwood Victoria 3125 Australia
5. School of Environmental and Forest Sciences, Box 352100; University of Washington; Seattle WA 98195 U.S.A.