The use of accessibility in defining sub-groups of small mammals from point sampled data
Point sampling is a method used to estimate the extent and size of a population of interest. Two approaches were used with this type of data to define sub-groups within a house mouse (Mus musculus domesticus) population studied by capturemarkrecapture. Buffering was used as an example of a deterministic method. The results were easy to interpret, but sensitive to the buffer distance and the arrangement of sample points. Creating an accessibility surface from the data was found to be much more suitable. Each sample point was weighted proportionately according to the number of mice caught there (other weighting methods are suggested for different types of study). A distance decay exponent was estimated from the dataset (beta=1.42) and used to implicitly incorporate the actual movements of mice into the calculation of accessibility. Reference is made to other uses of accessibility, noting that the application we have developed is a novel use of the methodology. The patterns within the accessibility surface were then described with morphometric feature characterisation, making the analogy with landscape analysis [Wood, J. (1996). Scale-based characterisation of digital elevation models. In D. Parker (Ed.), Innovations in GIS 3: selected papers from the third national conference GIS research UK (GISRUK) (pp. 163175). London: Taylor & Francis]. The sub-groups defined in this way were found to be in agreement with the expected results based on first-hand knowledge of the population, and can be used to characterise the dynamics of the population with respect to current ecological theory.
accessibility house mouse mus musculus domesticus capturemarkrecapture buffering geographic information system fragmented population