Components of detection probability

questions concerning analysis/theory using program PRESENCE

Components of detection probability

Postby efraser » Wed Jun 19, 2019 9:11 am

We are using a multi-season analysis in Presence to model variation in detectability (p) of red squirrels over the annual cycle and have been reading some of the detection probability literature. Detection probability is often described as having three components: probability of presence (related to abundance); probability of availability; and probability of detection given availability (e.g. Hostetter et al. 2019). Are the "p" estimates modelled by Presence considered to be the product of these three probabilities? If so, could you recommend the key references that describe this relationship? Also, given that we are doing a multi-season analysis, does the fact that we are modelling both colonization and extinction rates between seasons possibly mitigate the effect of changing abundance (probability of presence) on changing estimates of detectability?

Please excuse the repetition - we had originally posted this question on the general design and analysis board, but did not receive a response and realized that it is more a software-specific query. So are re-posting here. Many thanks.
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Re: Components of detection probability

Postby darryl » Wed Jun 19, 2019 4:30 pm

The devil is in the details. It all depends on your study design, field methods and how you're analysing the data in terms of how you should be interpreting any of the estimates that come out of the analysis. That said, using the regular single- or multi-season models p is often the product of availability and detection given available, but not always (again, depends on the above). We cover this sort of stuff in our book 'Occupancy estimation and modeling', more so in the 2nd edition (sorry for the shameless self-promotion). I'm sure some of it will also be covered in various papers on the design of occupancy studies.

Changing abundance will likely still result in changing detection (at species level), colonization and extinction won't necessarily account for that - it all depends how the change in abundance is manifesting (ie same occupancy and change in density, or change in occupancy and same density).

Hope that helps.
Darryl MacKenzie
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