Hello,
I am analyzing DNA data, which are collections of chimpanzee fecal material from searches across 624 sq km. I am using the 'polygon' detector type, and my polygons are 4x4 km grid squares that I drew over my searched area. I obtained a population density estimate of 0.25 (0.16-0.37) individuals/sq. km (perfectly reasonable for this savanna-woodland habitat). My complete data set includes 113 individuals, 38 recaptures, and 49 detectors used, 17 visited.
Previously, researchers had designated part of the region where I worked "suitable" chimpanzee habitat (presumably, the remaining areas "not so suitable"). In the interest of further investigating these designations, I divided my captures and traps data files into "suitable" and "unsuitable", and calculated the density estimates for each of these subsets. I obtained population density estimates of 0.39 (0.16-0.37) and 0.32 (0.22-0.46) for "suitable" and "unsuitable", respectively.
Clearly, the second analyses had smaller sample sizes, but would this be the sole factor driving the different results? For the second analyses, I had the following variables:
SUITABLE: 58 individuals, 12 recaptures, 30 detectors (12 visited)
UNSUITABLE: 55 individuals, 26 recaptures, 18 detectors (6 visited)
Also, does the number of detectors (i.e., my grid squares), which is randomly decided in this case, matter?
Thank you very much for your help.