True absences vs false presence

[jimborbs]

Hi,

We recently carried out occupancy survey for tigers in state of Arunachal Pradesh, India. Due to extremely difficult terrain, the sampling sites were inconsistent (grids were laid but we could not do it accordingly). In spite of more than 100 hours of man effort, we could not come across a single direct evidence of tigers, although secondary information from villagers/forest staffs in certain sites indicates tiger presence. Other variables collected includes human disturbance, hunting pressures and habitat.

Now I 'm confused as to whether I should use the secondary info as a surrogate for tiger presence (evidence) or not? Also due to the rugged and difficult terrain, since all the grids could not be covered, can we use the km walked for detecting signs as proportion of area sampled and thus occupied?

Any assistance would be highly appreciative.

Regards,
Jim

[jhines]

Jim,

Occupancy analysis has been done on sign of difficult to detect species, as well as human surveys. You might want to read 'Tigers on Trails' (Ecological Applications 2010), which used tiger sign along forest trails as occupancy data.

Jim

[jimborbs]

Thanks Jim....