Accounting for detectability and abundance in survey design for a declining species

Abstract

Aim: As populations decline they become harder to detect simply because there are fewer animals to observe. In such cases, survey effort that was once reliable may become inadequate and the species incorrectly labelled locally extinct, causing management efforts to cease. For declining populations, then, we need to determine the survey effort necessary to detect the species, assuming only a single individual is present at a site. Detectability, however, often varies wildly with seasonal, behavioural and environmental variables. Thus, we need statistical analyses and survey design which can deal with highly variable detection rates and allow us to detect even very small populations. This is e..