A comparison of two home range core estimators for Tibetan fox (Vulpes ferrilata)

Home range core has been defined as the area used intensively by an animal and which contains critical resources for living, such as cover, food, and if applicable, a denning or roosting location. The identification of home range core has received considerable interest among researchers, but it has proven difficult to come to consensus on the best way to quantify it in an objective and accurate way that yields biologically significant information. We documented 199 locations of 3 Tibetan foxes (Vulpes ferrihla) in Gouli Township, Dulan County, Qinghai Province during April 2006, September - October 2006, and January - April 2007. Using these locations, we estimated home range cores using both fixed kernel and harmonic mean methods based on the home range core identification principles of Seaman and Powell (1990). We compared these 2 methods to determine the better one for home range core estimation. Home range core size was influenced by total home range in both methods. Home range core estimated using the fixed kernel method was more sensitive to total home range area than that using the harmonic mean method, and variable coefficients varied greatly. Home range core size using the fixed kernel method was negatively correlated with sample size, whereas that using the harmonic mean was positively correlated with sample size. Area not actually in the animal' s home range was more easily included in the harmonic. However, to some extent this drawback can be eliminated when home range core was estimated. The harmonic mean method reflected the center of activity more precisely, and more locations of foxes were included in the home range core estimated. For our Tibetan foxes, fixed kernel home ranges showed some more consistency with varying sample size, but harmonic mean was suggested to be the better home range core estimator.