Gap crossing by chipmunks: an experimental test of landscape connectivity

Eastern chipmunks (Tamias striatus) are forest specialists common to eastern North America. Numerous studies suggest that chipmunks require fencerow corridors between woodlots to maintain functional connectivity in agricultural landscapes. We tested this hypothesis by conducting a homing experiment to assess whether chipmunks would cross nonforested gaps of different sizes. Chipmunks in 11 landscapes were translocated a constant distance of 220-250 m across gaps ranging in size from 0 (continuous forest) to 240 m (mostly gap). Logistic regression analysis demonstrated that the probability of an adult chipmunk returning to its home range was not related to the size of the gap that had to be crossed (chi(2) = 0.781, n = 60, P = 0.377, rho(2) = 0.011). Chipmunks crossed the entire range of gap sizes and there was no evidence of a threshold in connectivity. These results suggest that forest woodlots may be functionally connected for chipmunks even without fencerow corridors, and that landscape configuration in the study area may not have isolating effects on chipmunk populations. More empirical studies are required to identify whether functional connectivity thresholds are present in mammal populations as theoretical studies suggest.