Introduction

The number of invitations to contribute a chapter on a species was 224. The statistical aspects are not emphasized for two major reasons. The first is that the statistical problems of counting are universal; counting red blood cells on a plate presents the same statistical problems of sampling as does counting caribou from an airplane. The second reason is that elaborate statistical methods are rarely used except for a few species (commercial fish, whales). To capture or hold some vertebrates, permits must be obtained to comply with federal and state laws. Federal permits are necessary for migratory birds, endangered species, and certain marine mammals.