Patch specific SIFs in two-species models??

questions concerning analysis/theory using program PRESENCE

Patch specific SIFs in two-species models??

Postby nachoman » Wed Aug 10, 2016 5:30 pm

Hi all,

my data comes from spatially and temporally replicated cam trap records e.g. one camera-trap per patch, each patch surveyed a number of occasions.

I am primarily interested describing how interaction between species varies between patches. I am wondering whether two-species models output give some kind of SIF to describe the sign and magnitude of the interaction for EVERY PATCH, instead of the average estimate across patches.

Given that patches are surveyed a number of times maybe (perhaps) there’s a way to derive patch specific SIFs as a derived parameter, the same way that single season occupancy models give you psi-condicional site (=patch) specific estimates as model output. Actually, I can’t remember if multiple season occupancy models give you psi-condicional site (=patch) specific estimates FOR EVERY season as model output …(apologies but I am returning to occupancy model estimation after long holidays, I need to refresh my mind!).

Cheers,

N
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Re: Patch specific SIFs in two-species models??

Postby jhines » Thu Aug 11, 2016 11:13 am

For the single-season model, PRESENCE prints out the SIF as a derived parameter when the default (psiA,psiBA,psiBa) parameterization is selected. If any of the parameters which go into the calculation of phi (SIF), are site-specific, then the site-specific phi's will be printed.

With the alternate parameterization (psiA,psiB,phi), site-specific phi's will be printed if phi is modelled as a function of site-specific covariates.

For multi-season models, phi is not printed as a derived parameter, since it would apply only to the 1st season. I suppose it could be computed for other seasons, but would be very complicated, I think.

One solution to obtaining the seasonal phi's would be to run each season of data with the single-season model. Or, you could combine the single-season data into one large data-set, with season as a site-covariate.
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Re: Patch specific SIFs in two-species models??

Postby nachoman » Fri Aug 12, 2016 2:33 pm

Thanks James, SUPERuseful tip. Now let's see if the data behaves..
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