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.

Spatiotemporal distributions of mammals occurring in an agro-prairie ecosystem.

Anthropogenic activities since the European colonization of the North American Great Plains have drastically altered landscape composition and configuration, subsequently affecting native biodiversity. These contemporary human-modified landscapes may affect mammal species' distributions, diel activity patterns, habitat use, and interspecific interactions, though a better understanding of these effects on mammals occurring in remaining prairie landscapes is needed. To fill this gap, we surveyed 381 randomly selected sites in 2018, 2019, and 2020 using motion-sensing camera traps across the western part of the US state of Kansas (7,160,077 ha). Sites were separated by ≥2 km ( x ¯ $$ \overline{x} $$ = 8.16 km, SD = 3.61), and cameras were secured to a metal post 40 cm above ground and randomly oriented toward the north or south. We placed an olfactory attractant (mixture of skunk essence and petroleum jelly) on a wooden stake 3 m in front of each camera. Cameras were in place at each site for 28 consecutive days for each year. We manually identified all mammal species detected at each site, collating these data into a database that included taxonomic information for 14 families of mammals (Antilocapridae, Bovidae, Canidae, Cervidae, Cricetidae, Dasypodidae, Didelphidae, Erethizontidae, Felidae, Heteromyidae, Leporidae, Mephitidae, Mustelidae, Procyonidae, Sciuridae, and Muridae) comprising 28 total species. We recorded 31,178 mammal photographs (nonindependent events) over 27,954 camera trap nights during 2018 (n = 10,351), 2019 (n = 9478), and 2020 (n = 8125). Additionally, we included the time and date of each photocapture. Moreover, we gathered survey-specific data useful for modeling species-specific detection along with site-level habitat composition data taken at each site each year. These data will be useful for examining habitat use, species distributions, diel activity patterns, and spatiotemporal interactions between species and across guilds of mammals occurring in a rapidly changing agro-prairie ecosystem. There are no copyright restrictions, but we ask researchers to cite this paper when using these data for publication.

Demographic effects of a megafire on a declining prairie grouse in the mixed-grass prairie.

Recent studies have documented benefits of small, prescribed fire and wildfire for grassland-dependent wildlife, such as lesser prairie-chickens (Tympanuchus pallidicintus), but wildlife demographic response to the scale and intensity of megafire (wildfire >40,000 ha) in modern, fragmented grasslands remains unknown. Limited available grassland habitat makes it imperative to understand if increasing frequency of megafires could further reduce already declining lesser prairie-chicken populations, or if historical evolutionary interactions with fire make lesser prairie-chickens resilient. To evaluate lesser prairie-chicken demographic response to megafires, we compared lek counts, nest density, and survival rates of adults, nests, and chicks before (2014-2016) and after (2018-2020) a 2017 megafire in the mixed-grass prairie of Kansas, USA (Starbuck fire ~254,000 ha). There was a 67% decline in attending males on leks post-fire and a 57% decline in occupied leks post-fire. Despite population declines as indicated by lek counts, adult female breeding season survival ( S ^ ) was similar pre- ( S ^  = 0.65 ± 0.08 [SE]) and post-fire (0.61 ± 0.08), as was chick survival (pre-fire: 0.23 ± 0.07; post-fire: 0.27 ± 0.11). Nest survival appeared lower post-fire (pre-fire: 0.38 ± 0.06; post-fire: 0.20 ± 0.06), but did not differ at the 95% confidence interval. Nest density of marked females declined 73% in areas burned by megafire. Although lesser prairie-chickens persisted in the study area and we documented minimal effects on most demographic rates, reduced lesser prairie-chicken abundance and reproductive output suggests full recovery may take >3 years. Increased propensity for megafire resulting from suppression of smaller fires, compounded by climate change and woody encroachment, may impose a short-term (3-5 year) threat to already declining lesser prairie-chicken populations.

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.

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.

BASELINE PHYSIOLOGIC AND HEMATOLOGIC HEALTH IN WILD-CAUGHT MUSKRATS (ONDATRA ZIBETHICUS) FROM A NEAR-PRISTINE ECOSYSTEM IN NORTHERN MINNESOTA.

Muskrat (Ondatra zibethicus) populations show long-term and widespread declines across North America, necessitating research into potential mechanistic explanations, including population health. Previous research established reference hematology values, a proxy of individual health, of muskrats occurring in highly modified ecosystems. However, our knowledge of hematology metrics in muskrat populations occurring in more natural ecosystems is limited. We measured several hematological parameters of wild-caught muskrats (n = 73) in the Greater Voyageurs Ecosystem in northern Minnesota in 2018-2019 to establish baseline muskrat health in a relatively intact, near-pristine ecosystem. Additionally, we measured rectal temperature and heart and respiratory rates and collected whole blood for complete blood cell count assessment. We established baseline physiologic and hematologic reference ranges for the population and describe variations between total white blood cells, nucleated cell differentials, and basic erythron and platelet estimates and demonstrate methods of estimation to be poor proxies for more standardized counting methods. Our results establish a baseline to compare muskrat health assessments for populations affected by landscape change or in decline.

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.

Summer Precipitation Predicts Spatial Distributions of Semiaquatic Mammals.

Climate change is predicted to increase the frequency of droughts and intensity of seasonal precipitation in many regions. Semiaquatic mammals should be vulnerable to this increased variability in precipitation, especially in human-modified landscapes where dispersal to suitable habitat or temporary refugia may be limited. Using six years of presence-absence data (2007-2012) spanning years of record-breaking drought and flood conditions, we evaluated regional occupancy dynamics of American mink (Neovison vison) and muskrats (Ondatra zibethicus) in a highly altered agroecosystem in Illinois, USA. We used noninvasive sign surveys and a multiseason occupancy modeling approach to estimate annual occupancy rates for both species and related these rates to summer precipitation. We also tracked radiomarked individuals to assess mortality risk for both species when moving in terrestrial areas. Annual model-averaged estimates of occupancy for mink and muskrat were correlated positively to summer precipitation. Mink and muskrats were widespread during a year (2008) with above-average precipitation. However, estimates of site occupancy declined substantially for mink (0.56) and especially muskrats (0.09) during the severe drought of 2012. Mink are generalist predators that probably use terrestrial habitat during droughts. However, mink had substantially greater risk of mortality away from streams. In comparison, muskrats are more restricted to aquatic habitats and likely suffered high mortality during the drought. Our patterns are striking, but a more mechanistic understanding is needed of how semiaquatic species in human-modified ecosystems will respond ecologically in situ to extreme weather events predicted by climate-change models.

Risk factors for Toxoplasma gondii exposure in semiaquatic mammals in a freshwater ecosystem.

We assessed risk factors for Toxoplasma gondii exposure in semiaquatic mammals in east-central Illinois, US. This agricultural region has extensive drainage systems that could potentially transport T. gondii oocysts into the watershed. We used muskrats (Ondatra zibethicus) and American mink (Neovison vison) as sentinels of watershed contamination. We predicted individuals from larger subwatersheds would more likely be antibody-positive for T. gondii, as they were exposed to drainage from larger areas. We also evaluated amount of urban land cover within the subwatershed, proximity to farmsteads, and age of individuals in competing models of T. gondii infection. Antibodies to T. gondii were assayed in animal sera by modified agglutination tests (titer 25 or higher) and detected in 18 (60%) of 30 muskrats and 20 (77%) of 26 mink. Infection rates were ≥1.7 times higher than those typical for mammals in upland habitats in this region. Subwatershed size and age class were important predictors of T. gondii infection in muskrats (R(2) = 0.35). Models incorporating urban land cover and proximity to farmsteads had little support. None of our models of antibody prevalence in mink were well supported, possibly because mink are less strictly associated with riparian habitats. Because ~91% of our study area is devoted to agricultural production and urbanization, transport of T. gondii into freshwater ecosystems is likely facilitated by modified drainage practices common in these areas.

Hematologic and blood chemistry reference values for free-ranging muskrats (Ondatra zibethicus).

Baseline hematologic and serum chemistry values are used by veterinarians and wildlife biologists to identify abnormally high or low levels of particular blood parameters in a target species. This vital information can assist animal care providers in making informed decisions on the care of wildlife and help to determine diagnoses for certain illnesses. Published blood parameter values are not available for wild-caught muskrats (Ondatra zibethicus). We measured 27 blood parameter values from 29 free-ranging, riparian muskrats caught from June-November 2008 in east-central Illinois, USA, and compared mean values between adults and juveniles. Adult muskrats had higher levels of globulins (F(1,27)=6.394, P ≤ 0.018) and eosinophils (F(1,25)=6.883, P ≤ 0.015) than did juvenile muskrats, possibly because of increased exposure to parasites and allergens over time.