1. Given the long and dynamic history of anthropogenic disturbances to ecosystems, it is difficult to determine the drivers of past population declines. These uncertainties dilute the efficacy of conservation efforts and might hinder species and ecosystem recovery.

2. Niche quantification can be a useful tool for understanding drivers of past population declines. Niche parameters reflect key resources used, providing insight into the conditions needed to achieve population stability. By reconstructing a population’s niche position and space over a period of decline and comparing to historic baselines, shifts in the realized niche of a species can be assessed. Comparing shifts to historic information on resource availability and timing of declines can allow practitioners to identify probable drivers of species decline.

3. We demonstrated the utility of this technique by reconstructing parameters of isotopic dietary niche over a 130 year period and comparing isotopic niche reconstructions to land use and crop harvests during this same period via regression and Bayesian standard ellipsoid (SIBER) analyses. We use a formerly widespread but now endangered species, the eastern spotted skunk (Spilogale putorius), addressing the hypothesis that land use change and agricultural intensification led to a historical collapse of key dietary resources which correlates with population declines in this species. To help control for isotopic variability unrelated to population decline, we compare trends to those of a secure, but ecologically similar generalist mesocarnivore, the striped skunk (Mephitis mephitis), across the same spatiotemporal scale.

4. We present evidence that historic dietary changes occurred in spotted skunks in the early 1900s but not to the same degree in striped skunks. Changes in isotopic composition correspond with the temporal period of decline and are explained by concurrent changes in land use. These results support the hypothesis that loss of key dietary resources as a result of land use change and agricultural intensification played a significant role in population declines of spotted skunks in this region.

Stable isotope data obtained from hairs of museum specimens of eastern spotted skunk (Spilogale putorius) and striped skunk (Mephitis mephitis). Harvest data compiled from Kansas Fish and Game Commission and the United States Fish and the Wildlife Service Wildlife Leaflets Series. Landuse data compiled from the US Census of Agriculture. Additional notes in the README.txt

Please see README.txt