1. CSIRO Wildlife and Ecology, G.P.O. Box 284 Canberra, ACT 2601, Australia,
2. School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, U.S.A., and Northern Rockies Conservation Cooperative, Box 2705, Jackson, WY 83001, U.S.A,
3. Urban and Environmental Research Program, Research School for the Social Sciences, The Australian National University, Canberra, ACT 0200, Australia.
4. Current address: The Centre for Educational Development and Academic Methods, The Australian National University, Canberra, ACT 0200, Australia,