Rapid, large-scale anthropogenic landscape change increasingly challenges native species. The identification of factors affecting species persistence is needed to direct planning and land management.
I designed an individual-based simulation model to examine the relationship among 3 landscape elements (composition, configuration, connectivity) and the persistence of 2 woodland small mammals whose responses to habitat change lie towards opposite ends of a gradient.
I obtained habitat use and demographic and movement parameters for the less adaptable eastern chipmunk (Tamias striatus) from trapping and radio-telemetry studies in farmland near Ottawa. Chipmunks used woods and canopied fencerows, but not fields. Fencerow use was higher in summer than fall. Residents favoured woods. Daily movements of 400 m occurred in all sex/age groups. Linear ranges exceeded previous reports.
Model parameters for the more opportunistic white-footed mouse (Peromyscus leucopus) came from existing data from the same region. Mice also moved greater distances in farmland, but used corn and grain fields as well as wooded areas.
The simulations followed chipmunk and mouse populations over 25 years in landscapes with unique combinations of amount of woodland (10%, 30%, 50%), number of patches (2, 4, 8,), and level of connectivity (high, intermediate, low, none).
Connectivity was the best predictor of population persistence for chipmunks. Long survival times and low extinction rates occurred in model landscapes with high and intermediate quality connectivity and with 30% or more woodland. Chipmunk populations in unconnected landscapes and in 8 patch landscapes with only 10% woodland and low connectivity suffered high extinction rates. Highly variable populations were at greater risk of extinction, especially when woodland habitat was low. For behaviourally inflexible species, maintenance of landscape connectivity when habitat loss and fragmentation occur is vital to survival.
Survival rates for mice were high in all landscape patterns. Since mice were not restricted to woods and fencerows, all landscapes were highly connected for them and provided over 78% usable habitat. For opportunistic species able to use novel resources, landscape change may not be limiting.
The response of species to human-altered landscapes is an essential factor in predicting population persistence.