Quantifying spatial–temporal patterns in wildlife ranges using STAMP: A grizzly bear example

Abstract

Geographical spatial analysis approaches are ideally applied to studies of wildlife habitat use when spatial data, such as telemetry data or spatial ranges, are available. For instance, it is often desirable to quantify spatial–temporal patterns of home ranges, which are typically delineated as polygons and represent areas of habitat that support wildlife functions. Changes to home ranges over time are often presented as variation in mean polygon area. This two-dimensional approach ignores potentially important spatial–temporal characteristics of habitat use, including site fidelity, range contraction, and expansion. Using Spatial–Temporal Analysis of Moving Polygons (STAMP) we examined a set of movement data for a subpopulation of adult female grizzly bears (Ursus arctos) for the period from 1999 to 2003 in the Rocky Mountain foothills region of Alberta, Canada. Home range change was quantified over two-year periods and evaluated on the basis of variable offspring dependency (i.e., whether the females had no cubs, cubs-of-the-year (COY), or yearling cubs) and foraging season. Solitary bears showed the greatest amount of home range fidelity, with an increase in range size during the mating season. Female grizzly bears with offspring experienced substantial home range change. Sows with COY had a reduced maternal home range size, especially during mating season, while those with yearling offspring had an increased home range size. The patterns of home range change were consistent with those expected if some combination of mobility and infanticide were the driving ecological mechanisms. We conclude that offspring dependency does not impact the degree of site fidelity but does impact the nature of home range change experienced. We also suggest that the spatial–temporal change in female grizzly home ranges could be used to infer breeding status and as a population monitoring tool. A geographical approach to home range change provides a simple and quantitative approach to mapping spatial–temporal patterns of habitat use and animal movement.