Chapter 9 - More than Two Occupancy States

Abstract

The dynamics of species occurrence can also be of interest in situations where ‘occupancy’ is defined in terms of multiple (i.e., > two) states. Imperfect detection means the true occupancy state of surveyed units will not always be observed, and therefore creates ambiguity about true changes in occupancy state. This needs to be accounted for to enable reliable inferences about the underlying dynamic process, and factors that may affect those processes, to be made. Here, the concepts of Chapters 5 and 8 are combined to enable investigation of occupancy dynamics for situations with more than two occupancy states over multiple seasons, while incorporating imperfect detection. We refer to this as a multi-season multi-state occupancy model. The general framework presented in this chapter is very useful and provides the structure for a number of interesting extensions. We believe that multi-state occupancy models dramatically increase our ability to address interesting questions about ecological processes associated with concepts such as source–sink dynamics, disease spread, and changes in the (relative) abundance distribution of species.