Date of Award
8-1-2025
Degree Name
Doctor of Philosophy
Department
Agricultural Sciences
First Advisor
Nielsen, Clayton
Second Advisor
Bastille-Rousseau, Guillaume
Abstract
Extirpation of apex predators, caused primarily by anthropogenic alterations to natural environments and persecution, has led to mesocarnivore release in these areas. Mesocarnivore release is an ecological phenomenon in which mesocarnivores thrive in the absence of apex predator dominance within the carnivore hierarchy. Mesopredators fill this dominant role on the landscape as de facto apex predators, however, this can lead to changes in inter-guild species space use, predator-prey dynamics, activity patterns, and interspecific competition. Understanding patterns in wildlife spatial distributions, which indicate variability in habitat space use across spatiotemporal scales, is critical for developing effective management and conservation plans and leads to a better understanding of ecological processes. I used 2 independent camera trap datasets gathered throughout 16,058 km2 of southern Illinois, USA: one collected between 2008 – 2010 across 357 camera clusters and the other collected between 2022 – 2024 across 409 camera clusters. Using multiple occupancy analysis techniques and kernel density estimation, I quantified the influences of habitat features and co-occurrence of competing species on the spatiotemporal dynamics of 6 mesocarnivore guild members: coyote (Canis latrans), bobcat (Lynx rufus), red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), striped skunk (Mephitis mephitis), and raccoon (Procyon lotor). Naïve occupancy (i.e., ndetected/nsurveyed) of gray fox declined from 0.20 to 0.06 between 2008 – 2010 and 2022 – 2024. Predicted occupancy ranged from 0.01 – 0.47 using the past dataset while the contemporary model had predicted occupancy ranging from 0.02 – 0.10, a 4-fold decline in occupancy estimates across 99% of my study extent. Most habitat features had different directional effects on gray fox occupancy between the 2 temporal periods, illustrating the complexity of gray fox habitat preferences and a shift in their ecology. Intra-specific activity overlap was high (range = 0.79 - 0.95) for my focal species between decades, however, activity patterns of striped skunk, raccoon, and domestic dogs were significantly different. Intraspecific diel niche also changed for gray fox, striped skunk, and raccoon. There were 6 interspecific activity patterns amongst focal species that had experienced a change in their significance between decadal periods. Native large-bodied carnivores had consistent different activity patterns with smaller-bodied carnivores and domestic dogs between decades. Larger-bodied carnivore species may be altering activity patterns of smaller-bodied members in areas experiencing one-sided-ness from mesopredator release, thereby decreasing competition and negative interspecific interactions. Coyotes and bobcats exhibited stability in occupancy dynamics at both narrow (coyote: γ = 0.89 ± 0.13, ε = 0.11 ± 0.07; bobcat: γ = 1 ± 0.01, ε = 0.00 ± 0.05) and broad temporal (coyote: γ = 0.96 ± 0.06, ε = 0.09 ± 0.03; bobcat: γ = 0.87 ± 0.14, ε = 0.31 ± 0.09) scales, supporting the idea of established priority effects. The extinction rates of smaller-bodied mesocarnivores, red fox (narrow: ε = 0.19 ± 0.40, broad: ε = 0.605 ± 0.11), gray fox (narrow: ε = 0.59 ± 0.16, broad: ε = 0.90 ± 0.04), and striped skunks (narrow: ε = 0.24 ± 0.13, broad: ε = 0.76 ± 0.06) dramatically increased and were higher than colonization rates, another indication that the establishment and persistence of these species is waylaid by extreme competitive exclusion from larger-bodied mesocarnivores. Furthermore, exurban environments are potentially increasing the complexity of these interactions, providing access to human subsidized resources. Co-occurrence models suggested that native and non-native co-occurrence increased with the presence of anthropogenic landscape features, increasing the chances of interspecific competition, persecution from humans, and potential disease transmission. Overall, my dissertation highlights the complex interactions that native and non-native species have across spatiotemporal scales, and the implications they can have on the subordinate species' population persistence.
Access
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