Westward expansion of melanistic fox squirrels (Sciurus niger) in Omaha, Nebraska

Historically, melanistic fox squirrels have been found in Council Bluffs, Iowa, and along the Missouri River in Eastern Omaha, Nebraska. However, recent anecdotal observations suggest that the melanistic trait in fox squirrels is expanding westward into Omaha. Squirrels were surveyed in the autumn of 2010 and 2011 along transect lines within five major city sections and different habitat types; comparisons were made to a survey performed in 1973. Proportion of melanistic squirrels in Council Bluffs remained at levels similar to 1973 surveys (∼50% melanistic). Since 1973 melanistic fox squirrels have increased in Omaha, with a higher proportion of melanistic squirrels in northwest (7.4%) and northeast (7.6%) compared to southwest or southeast Omaha (4.6%). Melanistic squirrels were found in higher proportions in parks (12.1%) and residential (10.9%) habitats compared to business (6.1%), industrial (7.4%), or golf course (8.0%) habitats. Melanistic squirrels were also observed more frequently at colder temperatures than rufus squirrels. The results yielded significant variation in the percent of melanistic individuals in each section and suggest the proportion of melanistic individuals is increasing westward.