Query regarding camera-specific sampling windows in spOccupancy

[Tashi Dhendup]

Hi Jeff, 

I am fitting an occupancy model in `spOccupancy` using by-catch camera-trap data collected as part of a large-scale carnivore survey. The broader survey was conducted across multiple field divisions/landscapes, each of which carried out surveys within relatively compact time periods, although deployments among divisions were staggered and sometimes overlapped. I standardised detection histories to the first 120 days following deployment of each individual camera station, rather than using a common calendar window for the entire field division.

Would this camera-relative approach to defining sampling occasions and closure periods be considered statistically appropriate for spOccupancy occupancy models?

Thanks a lot. 

Best,
Tashi

[Jeffrey Doser]

Hi Tashi, 

Thanks for the question. Yes, this approach is a valid way for fitting models in spOccupancy, although how this impacts the resulting interpretation of the occupancy models is largely dependent on the specific system with which your working. The impact of this choice on the closure assumption (and thus the resulting way in which occupancy probability is interpreted) is largely dependent on the study species, their movement patterns, and how likely the closure assumption is likely to be violated over this time period. So, your approach is certainly valid, but you may wish to look more into the literature on camera traps and occupancy models to see how such decisions might have different impacts depending on characteristics of your study species. 

Jeff

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Jeffrey W. Doser, Ph.D.

Assistant Professor

Department of Forestry and Environmental Resources

North Carolina State University

Statistical Ecology and Forest Science Lab

Pronouns: he/him/his