The role of urbanization in shaping small mammal community patterns and population processes in the forests of the Lake Tahoe Basin

Human encroachment has dramatically changed natural disturbance patterns and forest stand structure in many western North America forests. In the Lake Tahoe basin, urban development has been rapid and has created a fragmented forest mosaic with considerable overlap of forest and urban boundaries. Some of the ecological consequences of urbanization include shifts in the abundance of native species, loss of sensitive species, and changes in overall community structure, which can impact ecosystem function. It is essential that we understand how development and land use are changing the composition, abundance, and population dynamics of native wildlife species so that land use and development can be directed in a way that maintains biological diversity. In order to assess the impact of human development, disturbance, and habitat on small mammal community structure and population dynamics, we sampled 72 forest patches across the Lake Tahoe basin along a gradient of urbanization from no (0%) to high (70%) development. We found that habitat heterogeneity and bare ground were important habitat components for small mammals. While we found the impact of urbanization on small mammal species richness and abundance to be limited, patterns of community composition did vary significantly with development. We also found that for several species survival decreased and movement propensity increased with development, which has implications for population persistence. Negative impacts of development on species’ distribution and primary population processes may be an early warning sign that habitat conditions for some species are deteriorated in urban areas.