Spatiotemporal shifts in distribution of a recolonizing black bear population

Abstract

Following one of the most successful relocations of a large carnivore species, American black bears (Ursus americanus; hereafter bears) have expanded from Arkansas to the Ozark Highlands of southern Missouri, USA, where they were potentially extirpated in the early 1900s. Our first objective was to estimate spatial and temporal shifts in probability of bear presence to understand the population distribution in Missouri. Our second objective was to assess which factors might influence any detected shifts. We used public sightings of bears to develop statewide spatial distribution models for early (1991–2003) and late (2004–2015) bear presence probability in Missouri using maximum entropy modeling and determine the rate and direction of population expansion. We evaluated the effects of environmental variables (e.g., land cover, roads) on bear presence probability and predicted the total area of three levels of bear presence probabilities. The average annual density of bear sightings increased temporally by about 3.4/1000 km2 in Missouri. The Ozark Highlands ecoregion contained the highest average annual density of sightings during both time periods. The bear presence probability increased spatially about 29 km in a north–northwest direction between the two time periods and the distribution became more dispersed over time. Our results corroborate prior findings suggesting bear presence is greatest in forests and rural areas. However, the increased importance of cultivated crops over time combined with the consistently positive relationship with roads indicates little negative effects from anthropogenic features on the bear presence probability in Missouri.