William L. Thompsonis an ecologist/biometrician with the National Park Service in Anchorage, Alaska, where he helps design long-term monitoring programs for plants and animals in five national parks in southwestern Alaska. He is senior author of Monitoring Vertebrate Populations (Academic Press, 1998). He is alsothe author of Sampling Rare or Elusive Species: Concepts, Designs, and Techniques for Estimating Population Parameters (Island Press, 2004).