The shape of a sampling area for occupancy

[katyhyaena]

Hi. I hope someone can help me with this question!

I am setting up an occupancy study for brown hyaenas using 20 camera trap stations.

The area I’m working in can be divided into three clearly defined geographic areas; one is along a long thin mountain range and the other two are flat lands north and south of the mountains. I want to conduct three separate closed occupancy surveys, one in each area so I can compare hyaena occupancy in the different habitats.I am confident of detecting brown hyaenas in all three of my proposed areas.

For camera trapping it is recommended to set up grids that resemble a circular shape rather than a narrow strip as this improves analysis. I can’t find a similar statement listed in any of the occupancy literature. Does this assumption hold true for occupancy as well? When designing my surveys I am concerned about the long thin strip of mountain that I will survey and how the high periphery to area ratio may affect my results.

On the north and south sides of the mountain I propose surveying rectangular shaped areas for ease of access and to increase distance from the mountain. Is it a problem that my three sampling areas aren’t of similar shape if they are each the same total size? Or should I make all my survey areas long and skinny so they are comparable?

Thanks so much!
Katy

[murray.efford]

Katy
'Occupancy' is a floppy parameter that can mean almost anything depending on the sampling design, so you're right to be concerned. I suggest you try and digest the discussion of these issues by Efford & Dawson (2012) in Ecosphere, and think about what it is you want to estimate. For 'occupancy' you would ideally sample a large set of well-defined units of habitat of constant size and shape.

For camera trapping it is recommended to set up grids that resemble a circular shape rather than a narrow strip as this improves analysis

This seems to be a hangover from pre-spatially-explicit-capture-recapture times - we have much more flexibility these days.
Murray