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Hi,

I would like to estimate population density using program DENSITY (and the Pollock robust design approach).
I use to move (slightly) each trap between sessions to minimize a trap-dependence effect.
As far as I have understood program DENSITY considers each sessions separately.

What is the consequence of having X-Y coordinates of traps changing across sessions?
Of course, this would lead to unique ID for each session as well.

Thank you very much
Giacomo

Giacomo
You're right that DENSITY considers sessions separately (it can handle data from the 'robust design', but doesn't at present 'connect' individuals between sessions or estimate survival etc.). The overall likelihood that is maximized is simply the product of the within-session likelihoods (using the assumption of independence).

I'm not sure what sort of consequence you have in mind. A practical consequence is that you are free to use a completely different trap layout (set of X-Y coordinates) for each session (check 'Allow multiple trap files' in Options | Input and, on the main screen, select multiple trap layout files). Be careful to verify that the order of files is what you intended - use 'Edit list' on the dropdown menu.

(Of course you can model within-session trap dependence if you think it's still a problem).
Hope this helps
Murray