Spatiotemporal overlap with invasive wild pigs (Sus scrofa) varies by species and season in a temperate ecosystem

Abstract

Wild pigs (Sus scrofa), which are invasive in many regions globally, can alter ecosystems and compete with native species through interference competition and resource exploitation. Wild pig impacts on other species may increase with greater niche overlap, which could vary over time based on environmental conditions, resource availability, or biological traits like diet, especially as seasonal variation in wild pig diet has been widely documented. A limited number of studies have assessed spatial or temporal overlap between native species and invasive wild pigs, with only a handful simultaneously assessing overlap in these niche dimensions. We investigated the potential for interspecific interactions involving invasive wild pigs in the Piedmont region of South Carolina, USA, by examining seasonal spatiotemporal overlap with other wildlife using N‐mixture models and diel activity overlap analyses. Site use by white‐tailed deer (Odocoileus virginianus) and coyote (Canis latrans) was negatively associated with wild pig activity in the fall, when the species had high diel activity overlap, indicating spatial partitioning could reduce interference competition with wild pigs in this season. Conversely, white‐tailed deer site use was positively associated with wild pig activity in the winter, suggesting higher spatial overlap may be necessary if resources are limited. Site use by bobcat (Lynx rufus) and nine‐banded armadillo (Dasypus novemcinctus) in the spring, along with raccoon (Procyon lotor) and wild turkey (Meleagris gallopavo) site use in the summer, was positively associated with wild pig activity. With the exception of diurnal wild turkey, diel activity overlap between these species and wild pigs was high, although temporal partitioning could have occurred at finer spatiotemporal scales than we examined. Our results collectively emphasize the importance of accounting for seasonal spatial and temporal responses by individual species to invasive wild pigs, with special consideration given to species in seasons where high niche overlap with wild pigs is anticipated.

Risk from a top predator and forest structure influence scavenging by smaller carnivores

“…Of our focal species, gray foxes were likely at the highest risk of predation by coyotes, considering coyote-specific mortality is well documented (e.g., Fedriani et al, 2000) and we observed gray foxes killed by coyotes in our study area. This may also explain why we did not detect red foxes at our carcasses, despite them being present in our study area (Saldo et al, 2023): predation risk from coyotes may be even greater for red foxes (Levi & Wilmers, 2012). We also found that bobcats fed more when understory cover was minimal.…”

“…We stratified carcass deployment locations based on coyote activity. We primarily used data from an established camera array in our study area (Saldo et al, 2023) to estimate coyote activity (Appendix S1). The array consisted of ~90 unbaited cameras deployed on dirt roads, each ~1 km apart (Figure 1).…”

Resource pulses shape seasonal and individual variation in the diet of an omnivorous carnivore

“…For blackberries, we established plots along dirt roads in our study area, in which we counted the number of ripe blackberries each week. We established four plots per site, and each site was associated with an existing wildlife camera in a 1 km 2 array (Saldo et al., 2023 ). We made sure to stratify our sites each year across various forest successional stages (early, middle, and late successional forest) because ripening timing could depend on the amount of sunlight blackberries get.…”

“…In 2020, we classified our each of our camera sites (Saldo et al., 2023 ) into four classes of vegetation (mature pines, immature pines, clear‐cut, mixed pine, and hardwood), then randomly chose one site from each class to count blackberries at. Once at the site, we set up four 3 x 1 m plots, in which we counted blackberries each week (Figure 2 ).…”