Mesocarnivore dynamics in a highly fragmented, yet highly permeable urban landscape

Background/Question/Methods

A fundamental objective of ecology is to understand the factors that dictate species diversity through space and time. Although habitat fragmentation plays an important role in dictating community dynamics, given the varying scales and complexity of spatially fragmented landscapes many gaps remain in our knowledge of how communities operate in these environments. 

Urbanization is an increasingly common source of habitat fragmentation that alters ecological processes, species distribution, and community richness.  However, unlike classic fragmented habitats (e.g.  oceanic islands), the urban landscape is permeable, such that species can persist in the matrix between patches. In addition, urban environments are complex, with spatial and temporal variation in ecological, environmental, and social factors that influence species diversity.

To better understand how ecological communities operate in fragmented, yet permeable, urban landscapes, we studied the dynamics of Chicago’s mesocarnivore guild. We deployed camera traps at ~100 sites distributed throughout Chicagoland in each season every year since 2010. We employed an information theoretic approach within a hierarchical, Bayesian framework that draws from single-species multi-season patch occupancy and multivariate autoregressive models to test how species, patch, and landscape-level covariates influence species richness and community structure of mesocarnivores in the highly urban landscape of Chicago, Illinois.

Results/Conclusions

For the five species of mesocarnivores that we observed throughout this study, patch colonization was significantly impacted by landscape level covariates including connectivity and housing density, while habitat features that influence community structure in other systems, such as patch area, had little effect. Community dynamics were strongly influenced by among-species differences in colonization and persistence rates and estimated species richness at sites increased as a function of patch connectivity, decreased with housing density, and exhibited strong seasonal variation.   Furthermore, sites rarely contained more than three species at a time, while median species richness was two.   

Our results suggest that within permeable urban landscapes, the processes that impact mesocarnivore movement and persistence occur at separate scales.  Landscape and patch level features appear to have the strongest influence on colonization whereas persistence may be the result of site-specific, temporally varying characteristics such as human visitation, local temperature, or food availability.  For species that reside within urban landscapes, patch area may underrepresent habitable area, thereby reducing its impact on colonization, persistence, and community structure.   By studying spatiotemporal community dynamics in an urban landscape, our study highlights gaps in existing theory and elucidates the factors necessary for conserving urban biodiversity.