Veon, J.T., E. Lassiter, E. Johansson, M. Shaw, L. McTgue, R. Gibson, A. Massey, and B.A. DeGregorio. 2023. Influence of Human Development and Predator Abundance on Virginia Opossum Occupancy, Abundance, and Activity Patterns. Journal of Zoology. doi:10.1111/jzo.13111
|
Abstract
|
Download
|
August 2023
|
As human development increases across the globe, wildlife are either pushed out of developed areas or adapt to survive in these novel, human-dominated landscapes. Many mammalian mesopredators, such as the Virginia opossum (<i>Didelphis virginiana</i>), have adapted to living alongside human development in order to take advantage of human-subsidized food, water, and shelter and may also benefit from being “shielded” by humans from their natural predators if those predator species are less able to coexist with humans or if they alter their behavior when living in proximity to humans (the human shield hypothesis). The human shield hypothesis has been used to explain the co-existence of dominant and subordinate mesopredators in some of North America’s largest cities. Our objective was to evaluate if patterns of Virginia opossum occupancy, abundance, and activity conformed to patterns consistent with the presence of a human shield. We used data from a coordinated continent-wide camera trapping study, Snapshot USA to estimate Virginia opossum occupancy, abundance, and activity and relate these measures to surrounding landscape and urbanization variables. We found that opossum occupancy was positively associated with an index of human activity (anthropogenic sound), although at very high levels of sound, opossum occurrence decreased. Furthermore, opossum in heavily forest areas were more likely to be detected in areas with nearby anthropogenic sound indicating a preference towards settling near humans. In areas with a high density of human housing, opossum relative abundance and predator abundance both increased suggesting that opossum were shielded from predators, whereas at low or moderate levels of housing density, opossum abundance did not increase although predator abundance did. We found that opossum were strictly nocturnal (99% of detections) and that they shifted their activity to being active earlier in the evening in the presence of high predator abundance. We found evidence that Virginia opossum are likely shielded by humans from their predators and this was most apparent when examining abundance and to some extent occupancy. These results help to explain why the Virginia opossum is such a successful urban-exploiter.
|
Veon, J.T., D.G. Krementz, L.W. Naylor, B.A. DeGregorio. 2023. Effects of landscape composition on winter mallard (Anas platyrhnchos) body condition in Eastern Arkansas. Journal of Wildlife Management
|
Abstract
|
Download
|
November 2023
|
Overwintering waterfowl with a higher body condition index are thought to be more likely to survive the winter and have increased productivity during the following breeding season. Body condition index in waterfowl should reflect the resources available to them locally. Here, we analyze the relationship of landscape composition on mallard (<i>Anas platyrhynchos</i>)<i> </i>body condition using a mass by wing length index (BCI) within the Lower Mississippi Alluvial Valley of Arkansas. We measured hunter-harvested mallards during the 2019-2020 and 2020-2021 duck hunting seasons. We found that mallards collected from areas with high proportions of water cover, woody wetlands, and open water within a 30-km radius had higher BCI. Conversely, we found that mallards collected from areas with higher proportions of herbaceous wetlands or human disturbance had lower BCI. Management actions focused on maintaining water levels for waterfowl to access food resources, while providing ample habitat that allows for resting, loafing, and other life cycle events free of human disturbance, will most likely increase BCI in mallards wintering in the Lower Mississippi Alluvial Valley.
|
Shamon, Hila. Et Al. 2024. Snapshot USA 2021: A third coordinated national camera trap survey of the United States - first trends. Ecology.doi.org/10.1002/ecy.4318
|
Abstract
|
Download
|
May 2024
|
SNAPSHOT USA is a multi-contributor camera trap survey designed to survey mammals across the United States. The growing Snapshot dataset is useful for tracking wildlife populations responses to changes in land use, land cover, and climate across spatial and temporal scales. Here we present the SNAPSHOT USA 2021 dataset, the third national camera trap survey across the U.S. Data were collected across 109 camera trap arrays and consists of 1715 camera sites, 1849 camera deployments, the effort equaled 73,959 camera trap nights, and resulted in 172,957 observations of free-ranging mammals, birds, and humans. As an example of the potential uses, we analyze all 3 years of survey data to examine the proportion of change in occupancy of two sympatric common carnivores and two sympatric common ungulates: red fox (Vulpes vulpes), coyote (Canis latrans), mule deer (Odocoileus hemionus), and white-tailed deer (Odocoileus virginianus). We considered annual arrays to be comparable if separated by < 10 km and represented similar habitat. White-tailed deer occupancy remained stable across all years (mean proportion 2021/2019: 1.03 ± 0.38 SD). Occupancy proportions (mean proportion 2021/2019) between years for the other species appear stable for mule deer (0.93 ± 0.8 SD), increasing for coyote (1.34 ± 0.56 SD), and decreasing for red fox (0.74 ± 0.79 SD), but in each case the variability between regions precludes significance at the national level. Data collected across years can detect changes in species occurrence, but assessment at the national level require examination of occurrence in relation to land cover and climate gradients.
|
McTigue, L.E., E.V. Lassiter, M. Shaw, E. Johansson, K. Wilson, and B.A. DeGregorio. 2023. Does daily activity overlap of mesocarnivores vary with human development? PLoS One. https://doi.org/10.1371/journal.pone.0288477
|
Abstract
|
Download
|
January 2024
|
Predation and competition can influence the behavior and activity patterns of co-occurring species. Often subordinate species will alter their activity patterns to avoid being active at the same time as larger, dominant species. Human development can complicate interspecies interactions, as not all wildlife responds to human activity in the same manner. While some species may alter their activity to avoid being active when humans are, others may be unaffected or may benefit from being active at the same time as humans to reduce predation risk or competition. To further explore this phenomenon, we used data from a coordinated national camera-trapping program (Snapshot USA) to explore the temporal activity overlap of a large, dominant mesocarnivore, the coyote (<i>Canis latrans</i>) with two subordinate species, Virginia opossum (<i>Didelphis virginiana</i>) and Northern raccoon (<i>Procyon lotor</i>) along a gradient of human development. We found all three species to be predominantly nocturnal and while the subordinate species showed modest changes to their activity patterns in response to increasing human development, the dominant coyote did not alter activity patterns in response to surrounding development. As a result, temporal activity overlap was generally high between all species regardless of development. It appears that competitive and predatory pressures between these three generalist species were insufficient to cause any of them to strongly alter their activity patterns.
|
McTigue, L. and B.A. DeGregorio. 2023. Effects of Landcover on Mesocarnivore Density Along an Urban to Rural Gradient. Global Ecology and Conservation.
|
Abstract
|
Download
|
November 2023
|
Human development has major implications for wildlife populations with urban-exploiters benefiting from human subsidized resources whereas urban-avoiders can vanish from the wildlife communities in highly developed areas. Therefore, understanding how the density of different species varies in response to landcover associated with human development can provide important insight into how wildlife communities are likely to change and provide a starting point for predicting the consequences of those changes. Here, we use estimated the population density of five common mesocarnivore species (coyote (<i>Canis latrans</i>), bobcat (<i>Lynx rufus</i>), red fox (<i>Vulpes vulpes</i>), raccoon (<i>Procyon lotor</i>), and Virginia opossum (<i>Didelphis virginiana)</i>) along an urban to rural gradient in a rapidly developing area of the United States. At each study site, we applied the random encounter model to data from motion-triggered cameras to calculate the density of our five focal species. We then evaluated variation in density for each species based on natural and anthropogenic landcover variables. Coyotes and raccoons occurred in the greatest densities in areas with high estimated anthropogenic noise, suggesting that both species are synanthropic and able to co-exist in areas of high human activity. High densities of these species in proximity to human activity has potential repercussions for wildlife-human conflict. Alternatively, Virginia opossum and red fox attained the greatest densities in open, developed areas (lawns, golf courses, cemeteries, and parks) and were absent (red fox) or rare (opossum) in natural areas. Opossum and red fox were capable of living alongside humans but did so by an association with these novel, human-created and maintained environments. We found no evidence that bobcat density varied along the urban to rural gradient studied but suggest that this may have been confounded by the small spatial scale of many of our sites in relation to this wide-ranging species. The density estimates we report here based on game camera data of unmarked animals were consistent with reports from the literature for these same species. Furthermore, our results show that several mesopredators attain very high densities in close proximity to humans which certainly has implications for increased conflict with humans and our pets, their role as predators in human-dominated environments, and the risk of disease transmission in and around people. Finally, our results show that the novel environments that spread with the human footprint support large numbers of mesopredators that may be absent or occur in low densities in undeveloped areas.
|
Kays et al. 2024. Climate, food, and umans Predict Mammal Communities in the United States. Diversity and Distributions 30(9): e13900. https://doi.org/10.1111/ddi.13900
|
Abstract
|
August 2024
|
The assembly of species into communities and ecoregions is the result of interacting factors that affect plant and animal distribution and abundance at biogeographic scales. Here, we empirically derive ecoregions for mammals to test whether human disturbance has become more important than climate and habitat resources in structuring communities. We analyzed data from 25 mammal species recorded by camera traps at 6,645 locations across the conterminous United States in a joint modeling framework to estimate relative abundance of each species. Climate was the most important predictor of mammal abundance overall, while human population density and agriculture were less important, with mixed effects across species. Seed production by forests also predicted mammal abundance, especially hard-mast tree species. We used a clustering analysis to describe eight broad and 16 narrow mammal communities. The mammal maps are similar to those of plants, with an east-west split driven by different dominant species of deer and squirrels. Communities vary along gradients of temperature in the east and precipitation in the west. Most fine-scale mammal community boundaries aligned with established plant ecoregions and were distinguished by regional specialists or shifts in the relative abundance of widespread species. Maps of potential ecosystem services provided by these communities suggest high herbivory in the Rocky Mountains and eastern forests, high invertebrate predation in the subtropical south, and greater predation pressure on large vertebrates in the west. Our results highlight the importance of climate to modern mammals and suggest that climate change will have strong impacts on mammal communities in the future.
|
Johansson, E.P., and B.A. DeGregorio. 2023. The Effects of Landscape and Yard Features on Mammal Diversity in Residential Yards. Urban Ecosystems.
|
Abstract
|
Download
|
October 2023
|
The human footprint is rapidly expanding, and wildlife habitat is continuously being converted to human residential properties. Most wildlife residing in developing areas are displaced to nearby undeveloped areas. However, some animals can co-exist with humans and acquire the necessary resources (food, water, shelter) within the human environment. This may be particularly true when development is low intensity, as in residential suburban yards. Yards are individually managed “greenspaces” that can provide a range of food (e.g., bird feeders, compost, gardens), water (bird baths and garden ponds), and shelter (e.g., brush-piles, outbuildings) resources and are surrounded by varying landscape cover. To evaluate which landscape and yard features influence the richness and diversity of the herbivores and mesopredators within residential yards in a rapidly developing region; we deployed wildlife game cameras in 46 residential yards in summer 2021 and 96 yards in summer 2022. We found that mesopredator diversity was negatively impacted by fences and positively influenced by the number of bird feeders present in a yard. Mesopredator richness increased with the amount of forest within 400m of the camera. Herbivore diversity and richness were positively influenced by the area of forest within 400m of the yard and by the area of garden space within the yard, respectively. Our results suggest that while landscape does play a role in the presence of wildlife in a residential area, homeowners also have agency over the richness and diversity of mammals using their yards based on the features they create or maintain on their properties.
|
Johansson, E.P. and B.A. DeGregorio. Predators in residential yards: influence of yard features on the occupancy, detections rates, and overlap of coyotes (Canis latrans), gray fox (Uyrocyon cinereoargenteus), and red fox (Vulpes vulpes). Wildlife Research
|
Abstract
|
Download
|
October 2024
|
Mammalian predators have historically been persecuted and struggle to persist in areas of human development. Our study aimed to find if predators were utilizing residential yards, how certain features influenced their occupancy, detection rates, and temporal activity overlap with each other. We found that predator occupancy of residential yards was influenced by yard level features as opposed to surrounding landscape composition. This means that homeowners have some agency to attract or deter predators from their yards primarily through the use of fences to deter coyote and maybe other predators. As residential lawns become a more prominent landcover type worldwide, managers could benefit from understanding how these lawns provide resources that benefit predators and other wildlife existing in suburban settings and how yard features can create hot spots of conflict with these species of wildlife.
|
DeGregorio, B.A., M. McElroy, and E.P. Johansson. 2023. Occupancy and Activity Patterns of Nine-Banded Armadillos (Dasypus novemcinctus) in a Suburban Environment. Diversity 15: https://doi.org/10.3390/d15080907.
|
Download
|
July 2023
|
|