Re-colonization and expansion of moose populations in North Dakota: Legacy of landscape modifications after the dust bowl?

Human-induced habitat fragmentation can significantly alter ecosystems by facilitating the expansion or invasion by new species. Since the Dust Bowl of the 1930’s, the prairie ecosystem of North Dakota has been significantly altered as a result of habitat conversion for the purpose of agriculture and erosion control.  We hypothesized that the recent range expansion of moose in to the prairie-coteau of North Dakota is the direct result of these changes to the landscape.  We expected that moose on the prairie would prefer non-native human-created habitats (planted woodlots and crop fields) to native habitat types (grasslands) and would have large home ranges relative to those of woodland moose because these human-created habitat types are patchily distributed and make up the smallest proportion of the overall landscape.  We fitted 14 moose in two study areas (woodland and prairie) with global positioning system (GPS) radio collars.  Moose locations were plotted over a geographic information system (GIS) map of available habitat types to compare observed habitat use to expected use based on habitat availability.  Annual home range size for individual moose was determined using a 95% adaptive-kernel estimator. Moose in the prairie study area showed a preference for planted woodlots and row crops while utilizing grassland types less than expected (χ²₃ = 3427, P<0.001).  Also, home range estimates were larger for prairie moose (119.2-295.5 km²) than for woodland moose (17.0-50.7 km²; t=5.2, P=0.002).  These results support the hypothesis that range expansion by moose into the prairie-coteau region is the result of conversion of mixed-grass prairie habitat to an agricultural mosaic of cropland and planted woodlots.