The effects of urbanization on population density, occupancy, and detection probability of wild felids

Abstract

Urbanization is a primary driver of landscape conversion, with far-reaching effects on landscape pattern and process, particularly related to the population characteristics of animals. Urbanization can alter animal movement and habitat quality, both of which can influence population abundance and persistence. We evaluated three important population characteristics (population density, site occupancy, and species detection probability) of a medium-sized and a large carnivore across varying levels of urbanization. Specifically, we studied bobcat and puma populations across wildland, exurban development, and wildland-urban interface (WUI) sampling grids to test hypotheses evaluating how urbanization affects wild felid populations and their prey. Exurban development appeared to have a greater impact on felid populations than did habitat adjacent to a major urban area (i.e., WUI); estimates of population density for both bobcats and pumas were lower in areas of exurban development compared to wildland areas, whereas population density was similar between WUI and wildland habitat. Bobcats and pumas were less likely to be detected in habitat as the amount of human disturbance associated with residential development increased at a site, which was potentially related to reduced habitat quality resulting from urbanization. However, occupancy of both felids was similar between grids in both study areas, indicating that this population metric was less sensitive than density. At the scale of the sampling grid, detection probability for bobcats in urbanized habitat was greater than in wildland areas, potentially due to restrictive movement corridors and funneling of animal movements in landscapes influenced by urbanization. Occupancy of important felid prey (cottontail rabbits and mule deer) was similar across levels of urbanization, although elk occupancy was lower in urbanized areas. Our study indicates that the conservation of medium- and large-sized felids associated with urbanization likely will be most successful if large areas of wildland habitat are maintained, even in close proximity to urban areas, and wildland habitat is not converted to low-density residential development.

Interspecific interactions between wild felids vary across scales and levels of urbanization

“…; Lewis et al. ). All occupancy analyses were conducted in program PRESENCE (Hines ) and models were ranked using Akaike information criteria corrected for small sample size (AIC c ; Burnham and Anderson ).…”

“…However, detection probabilities of each species were influenced by two covariates: one continuous covariate that measured human influence at each camera site (termed human development ) and a categorical covariate that characterized each of the sampling grids (termed grid ) (Lewis et al. ). The covariate human development measured the amount of human influence (Lewis et al.…”

“…) associated with each camera location and was created by digitizing each human occurrence point (HOP; residence or structure) in the study areas using ArcMap 10 geographic information system (GIS) software (ESRI, Redlands, CA) from color orthophotographs (Lewis et al. ). Using ArcToolBox in ArcMap 10, we fit a Gaussian kernel over each HOP, where the density, or influence, was greatest directly at the point of interest and decreased out to a specified radius of a circle (Lewis et al.…”

“…); radii ranged from 100–1000 m on the WS and 100–1500 m on the FR (Lewis et al. ). In GIS, each camera location was intersected with the cumulative kernel density of human development across each radius (Lewis et al.…”

“…; Lewis et al. ). By influencing animal behavior and demography, all forms of urbanization can potentially alter interactions between species.…”