🚀 go-pugleaf

I have been asked to help analyze some data being collected on desert
tortoises. Among other things, a goal of the study is to estimate the 
number of tortoises living in a 70 sq. mi. area in the Mohave desert
here in southern California. Data are being collected on the number
of "tortoise signs" (i.e., tracks and feces) in fixed triangular 
transects (four per square mile); these data will be converted to
numbers of tortoises using standard conversions.
My idea was to fit an interpolated surface of tortoise population
density (via kriging), then integrate this surface over the study
area to obtain an estimate of tortoise numbers. Obviously, there's
more to this than just what I've presented here, but this is the 
crux of my question. Is it considered OK to use the integral of an
interpolated surface as an estimate of population size in a study region
in this way (seems reasonable to me)? Does anyone know of experiences
that others have had in using this sort of procedure to estimate
wildlife populations? Right now, I reading books on spatial statistics
by Ripley, Haining, Cressie, Cliff&Ord, and Upton&Fingleton. Is 
there some other essential reference that I need?
Thanks in advance for any and all help.

Does Noel Cressie read this list? A former Masters' student of his
(Mark Bryan) is a good friend of mine.


Mark Andersen                   manderse@orion.oac.uci.edu
Dept. of Ecology and Evolutionary Biology