Geology topics

Emily Johansson

Publications and source records attributed to Emily Johansson.

3 recordsLinked to original sources

USGS2024

Does daily activity overlap of seven mesocarnivores vary based on human development?

Many species of wildlife alter their daily activity patterns in response to co-occurring species as well as the surrounding environment. Often smaller or subordinate species alter their activity patterns to avoid being active at the same time as larger, dominant species to avoid agonistic interactions. Human development can complicate interspecies interactions, as not all wildlife respond to human activity in the same manner. While some species may change the timing of 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 these patterns, we used data from a coordinated national camera-trapping program (Snapshot USA) to explore how the activity patterns and temporal activity overlap of a suite of seven widely co-occurring mammalian mesocarnivores varied along a gradient of human development. Our focal species ranged in size from the large and often dominant coyote ( Canis latrans ) to the much smaller and subordinate Virginia opossum ( Didelphis virginiana ). Some species changed their activity based on surrounding human development. Coyotes were most active at night in areas of high and medium human development. Red fox ( Vulpes vulpes ) were more active at dusk in areas of high development relative to areas of low or medium development. However, because most species were primarily nocturnal regardless of human development, temporal activity overlap was high between all species. Only opossum and raccoon ( Procyon lotor ) showed changes in activity overlap with high overlap in areas of low development compared to areas of moderate development. Although we found that coyotes and red fox altered their activity patterns in response to human development, our results showed that competitive and predatory pressures between these seven widespread generalist species were insufficient to cause them to substantially alter their activity patterns.

PLoS ONE↗

USGS2023

Influence of human development and predators on patterns of Virginia opossum occupancy, abundance, and activity

As human development continues to expand, wildlife must relocate or adapt to survive. Many mammalian mesopredators, such as the Virginia opossum ( Didelphis virginiana ), have adapted to living alongside human development. Furthermore, top-down predation pressure may be altered in nuanced ways within the human environment. Species such as opossums may be shielded from predation by human development or behavioral changes in predators. Understanding how dominant and subordinate mesopredators co-exist across natural and developed areas will provide insight into how wildlife communities are structured. Our objective was to evaluate how opossum occupancy, abundance, and activity were associated with human development and the relative abundance of their predators. We used data from a nationwide camera trapping study, Snapshot USA, to estimate opossum occupancy, abundance, and activity. We related these measures to the surrounding landscape and urbanization variables. We found that opossum occupancy was positively associated with anthropogenic sound (a surrogate for human activity). Furthermore, opossums in heavily forested areas were more likely to be detected in locations with higher predicted anthropogenic sounds. In areas with a high density of human housing, opossum relative abundance increased when predator abundance increased. We also found opossums were strictly nocturnal and shifted their activity to earlier in the evening in the presence of high predator abundance. Our results suggest that humans and their urban development can have multidimensional impacts on opossum behavior and occurrence, and could facilitate changes in predator–prey dynamics. Future research should evaluate if the association of opossums with urban areas is due to human-subsidized resources or caused by reduced mortality from altered predator–prey dynamics.

Journal of Zoology↗

USGS2023

Effects of landscape cover and yard features on feral and free-roaming cat (Felis catus) distribution, abundance and activity patterns in a suburban area

Feral and free-roaming domestic cats ( Felis catus ) are invasive predators throughout the world. In some areas, cats occur in higher densities than native mammalian predators and can have severe effects upon prey populations. We set 48 wildlife game cameras in residential yards in Arkansas, USA, to evaluate which landscape and yard features influenced cat abundance occurring in yards. In addition, we quantified the daily activity patterns of free-roaming cats and explored how habitat features or predator activity influenced the timing of cat activity. We found that cats were present in 70.8% of yards with an average of three recognizable individuals per yard. Abundance of cats was higher than all native mesopredators except for raccoon ( Procyon lotor ) and Virginia opossum ( Didelphis virginiana ). Cat abundance and minimum population decreased when forest cover was high within 400 m of the camera. Cats were active at all times of the day but tended to be more diurnal in areas closer to city centers or in agricultural settings. Conversely, cats were more nocturnal later in the summer and in areas that had high levels of predator activity. Our results indicate that cats are widespread in this region and their relative abundance is driven more by landscape features than by yard features, possibly due to their large home ranges. Cats may alter their activity to better coexist with predators. Alteration in yard features is unlikely to be an effective deterrent for cats and more direct control measures may be necessary.

Arkansas↗