Vienna University of Economics and Business Administration. (2003). The R project for statistical computing. Date accessed (7th October 2004). http://www.r-project.org. Williams, B.K., Nichols, J.D., & Conroy, M.J. (2002) Analysis and management ofanimal populations. Academic Press, San Diego, California, US. Wilson, K.R. & Anderson, D.R. (1985) Evaluation of Two Density Estimators of Small Mammal Population Size. Journal ofMammalogy, 66, 13-21. Yoccoz, N.G., Nichols, J.D., & Boulinier, T. (2001) Monitoring of biological diversity in space and time; concepts, methods and designs. Trends in Ecology and Evolution, 16, 446-453.