Density and linkage estimators of home range: Nearest-neighbor clustering defines multinuclear cores

Methods used to estimate home ranges from point locations are based either on densities of locations or on link distances between locations. The densi ty-based methods estimate ellipses and contours. The other class minimizes sums of link distances, along edges of polygons or to range centers or betw een locations. We propose a new linkage method, using nearest-neighbor dist ances first to exclude outlying locations and then to define a multinuclear outlier-exclusive range core (OEC) by cluster analysis. The assumption beh ind exclusion of outliers. that movements inside and outside range cores in volve different activities, was supported by data from radio-tagged Common Buzzards (Buteo buteo). We compared the new method with other techniques by using location data from each of 28 goshawks, 114 buzzards, 138 gray squir rels, and 14 red squirrels. Range structure statistics from OECs showed mar ked differences between species in numbers and extent of core nuclei. Range analysis displays illustrated relationships of range area with age categor ies, food supply. population density, and body mass within species. The OEC S gave highly significant results in three of five within-species tests, pe rhaps because animal movements in these cases were affected by coarse-grain ed habitat boundaries. When movements were likely to have been influenced b y diffuse social interactions and foraging for scattered prey, the most sig nificant results were from density-based estimators, especially kernel cont ours that had been optimized by least-squares cross validation. We recommen d use of both density and linkage estimators of home range until a basis fo r a priori choices has been established.