Effects of European common reed on Blanding's turtle spatial ecology

Abstract

European common reed (Phragmites australis; common reed) is an aggressive invader of North American wetlands that forms homogenous patches and replaces native flora. Dense patches of common reed generally provide poor habitat for many species, although specific effects on at-risk turtles are largely unknown. We created 3 predictive scenarios to relate the amount of common reed in the landscape to amount of effective habitat for Blanding's turtles (Emydoidea blandingii) and investigated the spatial ecology of 46 adult Blanding's turtles using Euclidean distance analysis within 2 wetland complexes in southern Ontario, Canada. At the home-range scale, we identified a positive association between turtle home ranges and common reed. At the individual scale, turtle radio-locations were significantly farther from common reed patches than from random points, consistent with the hypothesis that they avoided common reed patches locally. When we analyzed habitat selection by sex, results were similar to population-level results except for nesting females. During nesting migrations, females did not avoid common reed patches at the individual scale but instead interacted with common reed, potentially placing themselves at risk of being stranded within dense patches. Our results are consistent with our dynamic home range plus saturation hypothesis that invasion of common reed reduces the amount of effective habitat for at-risk turtles in wetlands because Blanding's turtles significantly avoided common reed patches at individual scales. Management of common reed is an important step to restore habitat for Blanding's turtles and future research is needed to determine best restoration practices. © 2018 The Wildlife Society.