Population genomic structure of a widespread, urban-dwelling mammal: The eastern grey squirrel (Sciurus carolinensis).

Urbanization is a persistent and widespread driver of global environmental change, potentially shaping evolutionary processes due to genetic drift and reduced gene flow in cities induced by habitat fragmentation and small population sizes. We tested this prediction for the eastern grey squirrel (Sciurus carolinensis), a common and conspicuous forest-dwelling rodent, by obtaining 44K SNPs using reduced representation sequencing (ddRAD) for 403 individuals sampled across the species' native range in eastern North America. We observed moderate levels of genetic diversity, low levels of inbreeding, and only a modest signal of isolation-by-distance. Clustering and migration analyses show that estimated levels of migration and genetic connectivity were higher than expected across cities and forested areas, specifically within the eastern portion of the species' range dominated by urbanization, and genetic connectivity was less than expected within the western range where the landscape is fragmented by agriculture. Landscape genetic methods revealed greater gene flow among individual squirrels in forested regions, which likely provide abundant food and shelter for squirrels. Although gene flow appears to be higher in areas with more tree cover, only slight discontinuities in gene flow suggest eastern grey squirrels have maintained connected populations across urban areas in all but the most heavily fragmented agricultural landscapes. Our results suggest urbanization shapes biological evolution in wildlife species depending strongly on the composition and habitability of the landscape matrix surrounding urban areas.

Strolling through a Century: Replicating Historical Bird Surveys to Explore 100 Years of Change in an Urban Bird Community.

AbstractIn 1898, Herbert and Alice Walter started a 5-year survey of birds in Lincoln Park-the largest park in Chicago, Illinois-and summarized their data in an urban birding field guide, Wild Birds in City Parks. Twenty-nine years later, William Dreuth compared the relative frequency of species in the Walters' study to that in his own 5-year Lincoln Park survey. Between 2012 and 2015, we replicated these surveys to investigate a century of bird diversity and community composition change in urban Chicago. While species richness did not change, community composition did. We found that (1) species with a greater diet breadth and (2) species that increased in statewide occupancy were more likely to increase in frequency over time. We conclude that factors at multiple scales brought temporal changes to Chicago's bird community. Overall, this survey highlights the slow and subtle ways in which species may respond to a century of urban intensification.

Wealth and urbanization shape medium and large terrestrial mammal communities.

Urban biodiversity provides critical ecosystem services and is a key component to environmentally and socially sustainable cities. However, biodiversity varies greatly within and among cities, leading to human communities with changing and unequal experiences with nature. The "luxury effect," a hypothesis that predicts a positive correlation between wealth, typically measured by per capita income, and species richness may be one indication of these inequities. While the luxury effect is well studied for some taxa, it has rarely been investigated for mammals, which provide unique ecosystem services (e.g., biological pest control) and exhibit significant potential for negative human-wildlife interactions (e.g., nuisances or conflicts). We analyzed a large dataset of mammal detections across 20 North American cities to test whether the luxury effect is consistent for medium- to large-sized terrestrial mammals across diverse urban contexts. Overall, support for the luxury effect, as indicated by per capita income, was inconsistent; we found evidence of a luxury effect in approximately half of our study cities. Species richness was, however, highly and negatively correlated with urban intensity in most cities. We thus suggest that economic factors play an important role in shaping urban mammal communities for some cities and species, but that the strongest driver of urban mammal diversity is urban intensity. To better understand the complexity of urban ecosystems, ecologists and social scientists must consider the social and political factors that drive inequitable human experiences with nature in cities.

Landscape-scale differences among cities alter common species' responses to urbanization.

Understanding how biodiversity responds to urbanization is challenging, due in part to the single-city focus of most urban ecological research. Here, we delineate continent-scale patterns in urban species assemblages by leveraging data from a multi-city camera trap survey and quantify how differences in greenspace availability and average housing density among 10 North American cities relate to the distribution of eight widespread North American mammals. To do so, we deployed camera traps at 569 sites across these ten cities between 18 June and 14 August. Most data came from 2017, though some cities contributed 2016 or 2018 data if it was available. We found that the magnitude and direction of most species' responses to urbanization within a city were associated with landscape-scale differences among cities. For example, eastern gray squirrel (Sciurus carolinensis), fox squirrel (Sciurus niger), and red fox (Vulpes vulpes) responses to urbanization changed from negative to positive once the proportion of green space within a city was >~20%. Likewise, raccoon (Procyon lotor) and Virginia opossum (Didelphis virginiana) responses to urbanization changed from positive to negative once the average housing density of a city exceeded about 700 housing units/km2 . We also found that local species richness within cities consistently declined with urbanization in only the more densely developed cities (>~700 housing units/km2 ). Given our results, it may therefore be possible to design cities to better support biodiversity and reduce the negative influence of urbanization on wildlife by, for example, increasing the amount of green space within a city. Additionally, it may be most important for densely populated cities to find innovative solutions to bolster wildlife resilience because they were the most likely to observe diversity losses of common urban species.

Urbanization alters predator-avoidance behaviours.

Urbanization is considered the fastest growing form of global land-use change and can dramatically modify habitat structure and ecosystem functioning. While ecological processes continue to operate within cities, urban ecosystems are profoundly different from their more natural counterparts. Thus, ecological predictions derived from more natural ecosystems are rarely generalizable to urban environments. In this study, we used data from a large-scale and long-term camera trap project in Chicago IL, USA, to determine whether urbanization alters predator-avoidance behaviour of urban prey species. We studied three behavioural mechanisms often induced by the fear of predation (spatial distribution, daily activity patterns and vigilance) of white-tailed deer (Odocoileus virginianus) and eastern cottontail (Sylvilagus floridanus) when coyote (Canis latrans)-an urban apex predator-was present. We found no evidence of spatial segregation between coyote and either prey species. Furthermore, neither white-tailed deer nor eastern cottontail changed their daily activity or increased vigilance in urban areas when coyotes were present. Eastern cottontail, however, had their uppermost level of vigilance in highly urban sites when coyotes were absent. Our study demonstrates that predator-prey dynamics might be modified in urban ecosystems-moving from what is traditionally thought of as a two-player system (predator and prey) to a three-player system (predator, prey and people).

Need for multiscale planning for conservation of urban bats.

For over a century there have been continual efforts to incorporate nature into urban planning. These efforts (i.e., urban reconciliation) aim to manage and create habitats that support biodiversity within cities. Given that species select habitat at different spatial scales, understanding the scale at which urban species respond to their environment is critical to the success of urban reconciliation efforts. We assessed species-habitat relationships for common bat species at 50-m, 500-m, and 1 km spatial scales in the Chicago (U.S.A.) metropolitan area and predicted bat activity across the greater Chicago region. Habitat characteristics across all measured scales were important predictors of silver-haired bat (Lasionycteris noctivagans) and eastern red bat (Lasiurus borealis) activity, and big brown bat (Eptesicus fuscus) activity was significantly lower at urban sites relative to rural sites. Open vegetation had a negative effect on silver-haired bat activity at the 50-m scale but a positive effect at the 500-m scale, indicating potential shifts in the relative importance of some habitat characteristics at different scales. These results demonstrate that localized effects may be constrained by broader spatial patterns. Our findings highlight the importance of considering scale in urban reconciliation efforts and our landscape predictions provide information that can help prioritize urban conservation work.

Mammal diversity and metacommunity dynamics in urban green spaces: implications for urban wildlife conservation.

As urban growth expands and natural environments fragment, it is essential to understand the ecological roles fulfilled by urban green spaces. To evaluate how urban green spaces function as wildlife habitat, we estimated mammal diversity and metacommunity dynamics in city parks, cemeteries, golf courses, and natural areas throughout the greater Chicago, Illinois, USA region. We found similar α-diversity (with the exception of city parks), but remarkably dissimilar communities in different urban green spaces. Additionally, the type of urban green space greatly influenced species colonization and persistence rates. For example, coyotes (Canis latrans) had the highest, but white-tailed deer (Odocoileus virginianus) the lowest probability of persistence in golf courses compared to other green space types. Further, most species had a difficult time colonizing city parks even when sites were seemingly available. Our results indicate that urban green spaces contribute different, but collectively important, habitats for maintaining and conserving biodiversity in cities.

Geographical Variation in Social Determinants of Female Breast Cancer Mortality Across US Counties.

Importance: Breast cancer mortality is complex and traditional approaches that seek to identify determinants of mortality assume that their effects on mortality are stationary across geographic space and scales. Objective: To identify geographic variation in the associations of population demographics, environmental, lifestyle, and health care access with breast cancer mortality at the US county-level. Design, Setting, and Participants: This geospatial cross-sectional study used data from the Surveillance, Epidemiology, and End Results (SEER) database on adult female patients with breast cancer. Statistical and spatial analysis was completed using adjusted mortality rates from 2015 to 2019 for 2176 counties in the US. Data were analyzed July 2022. Exposures: County-level population demographics, environmental, lifestyle, and health care access variables were obtained from open data sources. Main Outcomes and Measures: Model coefficients describing the association between 18 variables and age-adjusted breast cancer mortality rate. Compared with a multivariable linear regression (OLS), multiscale geographically weighted regression (MGWR) relaxed the assumption of spatial stationarity and allowed for the magnitude, direction, and significance of coefficients to change across geographic space. Results: Both OLS and MGWR models agreed that county-level age-adjusted breast cancer mortality rates were significantly positively associated with obesity (OLS: ß, 1.21; 95% CI, 0.88 to 1.54; mean [SD] MGWR: ß, 0.72 [0.02]) and negatively associated with proportion of adults screened via mammograms (OLS: ß, -1.27; 95% CI, -1.70 to -0.84; mean [SD] MGWR: ß, -1.07 [0.16]). Furthermore, the MGWR model revealed that these 2 determinants were associated with a stationary effect on mortality across the US. However, the MGWR model provided important insights on other county-level factors differentially associated with breast cancer mortality across the US. Both models agreed that smoking (OLS: ß, -0.65; 95% CI, -0.98 to -0.32; mean [SD] MGWR: ß, -0.75 [0.92]), food environment index (OLS: ß, -1.35; 95% CI, -1.72 to -0.98; mean [SD] MGWR: ß, -1.69 [0.70]), exercise opportunities (OLS: ß, -0.56; 95% CI, -0.91 to -0.21; mean [SD] MGWR: ß, -0.59 [0.81]), racial segregation (OLS: ß, -0.60; 95% CI, -0.89 to -0.31; mean [SD] MGWR: ß, -0.47 [0.41]), mental health care physician ratio (OLS: ß, -0.93; 95% CI, -1.44 to -0.42; mean [SD] MGWR: ß, -0.48 [0.92]), and primary care physician ratio (OLS: ß, -1.46; 95% CI, -2.13 to -0.79; mean [SD] MGWR: ß, -1.06 [0.57]) were negatively associated with breast cancer mortality, and that light pollution was positively associated (OLS: ß, 0.48; 95% CI, 0.24 to 0.72; mean [SD] MGWR: ß, 0.27 [0.04]). But in the MGWR model, the magnitude of effect sizes and significance varied across geographical regions. Inversely, the OLS model found that disability was not a significant variable for breast cancer mortality, yet the MGWR model found that it was significantly positively associated in some geographical locations. Conclusions and Relevance: This cross-sectional study found that not all social determinants associated with breast cancer mortality are spatially stationary and provides spatially explicit insights for public health practitioners to guide geographically targeted interventions.

Urbanization, climate and species traits shape mammal communities from local to continental scales.

Human-driven environmental changes shape ecological communities from local to global scales. Within cities, landscape-scale patterns and processes and species characteristics generally drive local-scale wildlife diversity. However, cities differ in their structure, species pools, geographies and histories, calling into question the extent to which these drivers of wildlife diversity are predictive at continental scales. In partnership with the Urban Wildlife Information Network, we used occurrence data from 725 sites located across 20 North American cities and a multi-city, multi-species occupancy modelling approach to evaluate the effects of ecoregional characteristics and mammal species traits on the urbanization-diversity relationship. Among 37 native terrestrial mammal species, regional environmental characteristics and species traits influenced within-city effects of urbanization on species occupancy and community composition. Species occupancy and diversity were most negatively related to urbanization in the warmer, less vegetated cities. Additionally, larger-bodied species were most negatively impacted by urbanization across North America. Our results suggest that shifting climate conditions could worsen the effects of urbanization on native wildlife communities, such that conservation strategies should seek to mitigate the combined effects of a warming and urbanizing world.

Mammals adjust diel activity across gradients of urbanization.

Time is a fundamental component of ecological processes. How animal behavior changes over time has been explored through well-known ecological theories like niche partitioning and predator-prey dynamics. Yet, changes in animal behavior within the shorter 24-hr light-dark cycle have largely gone unstudied. Understanding if an animal can adjust their temporal activity to mitigate or adapt to environmental change has become a recent topic of discussion and is important for effective wildlife management and conservation. While spatial habitat is a fundamental consideration in wildlife management and conservation, temporal habitat is often ignored. We formulated a temporal resource selection model to quantify the diel behavior of 8 mammal species across 10 US cities. We found high variability in diel activity patterns within and among species and species-specific correlations between diel activity and human population density, impervious land cover, available greenspace, vegetation cover, and mean daily temperature. We also found that some species may modulate temporal behaviors to manage both natural and anthropogenic risks. Our results highlight the complexity with which temporal activity patterns interact with local environmental characteristics, and suggest that urban mammals may use time along the 24-hr cycle to reduce risk, adapt, and therefore persist, and in some cases thrive, in human-dominated ecosystems.

Making wildlife welcome in urban areas.

Careful design of the green spaces in cities will benefit both wild animals and humans.