ABSTRACT
Conventional methods for estimating abundance relied on physically capturing, then marking the individual animal, then releasing it, and returning to recapture it at a later time. The simplest class of capture-recapture models relies on a closed-population assumption, meaning that the population being surveyed is not changing in abundance due to immigration, emigration, births, or deaths during the survey period. The parameter expanded data augmentation approach allows using a homogeneous occupancy model to estimate abundance because of the similarities of the different data types and it has been extended to several other settings. The design of occupancy models is to characterize and account for individual-level heterogeneity in capture probability to more accurately estimate abundance. In particular, some studies leverage spatial information, assumptions about the distribution of animals, and the way individuals are detected to help estimate population abundance. Distance sampling and spatial-capture recapture models are examples of methods that rely on spatially explicit information to facilitate abundance estimation.
