The Spatial Ecology of Wild Pigs (Sus scrofa) in Southwest Florida

TR Number
Date
2023-01-23
Journal Title
Journal ISSN
Volume Title
Publisher
Virginia Tech
Abstract

Wild pigs (Sus scrofa) are among the world's most destructive mammalian invasive species, and mitigating farther range expansion will require a thorough understanding of movement behavior, diel activity patterns, space use, and resource selection. Currently, limited empirical evidence is available on the ecology of wild pigs in Southwest Florida. Therefore, I examined how wild pigs behaviorally modified their movements and diel activity patterns in response to individual and environmental covariates. I investigated space use dynamics (e.g., home range size and seasonal variation) and evaluated how individual and environmental variation influenced home range size. Next, I determined how fine-scale movement patterns and resource selection of wild pigs are affected by temperature and time of day, and how those resources changed at broad and fine-scales, given their availability. I found that as temperature increased, the probability of foraging increased while the probability of traveling decreased. Foraging behavior occurred predominately between 8:00 and 17:00, and traveling behavior occurred predominately between 18:00 and 7:00, thereby indicating wild pigs were cathemeral. Home range size ranged from 2.6 to 35.8 km2 and averaged 13.0 km2 (n=16). Finally, home range size increased as the proportion of pasture increased and decreased as the proportion of wetlands increased, indicating that resources in agricultural areas were more diffuse than in natural habitats. At the broad (i.e., home range selection) and fine-scale (i.e., within home range) wild pigs selected for wetlands, forests, and pastures. Wild pig movement tended to be tortuous in forested and cropland habitats, but more directed in pasture habitats. Slower movements (i.e., smaller steps) and more directed (i.e., fewer turning) steps were observed during warmer temperatures, particularly avoiding croplands when temperatures were warmer. Wild pigs avoided wetland habitats during dusk and night hours and cropland habitats during dawn hours. Wild pigs selected for forested habitats during night and dawn hours, possibly in response to human activity. In addition, I found that wild pigs were less likely to step into a location with a daily temperature of 35.7°C than 16.1 C°. Wild pigs were less likely to choose warmer locations and more likely to select intermediate temperatures, thus avoiding locations with extremely low or high daily temperatures. Also, I found that wild pigs were more likely to select home ranges nearer to wetlands, forests, and pastures, while avoiding areas near cropland habitats. However, within their home ranges they were more likely to select habitats farther from croplands, forests, and wetlands. My findings reinforce the importance of wetlands, forests and pastures to wild pig selection of home ranges, where they likely utilize these landcover types for thermoregulation (e.g. forests and wetlands) and for foraging resources (e.g. pastures). Within their home ranges wild pigs may avoid forests and wetlands due to perceived predation risk being higher in those habitats, thus causing wild pigs to forgo higher quality resources to reduce risk. These results contribute information useful to wildlife managers to better predict which landcover types provide refuge (e.g., wetlands and forests) or potential movement corridors (e.g., pasture and cropland habitats) for wild pigs. In Southwest Florida, wild pigs have broad inter-individual variation in home range size, are strongly regulated by temperature, and are largely dependent on wetlands and forests to meet their energetic demands.

Description
Keywords
Movement ecology, resource selection, spatial ecology, space use, Sus Scrofa, wild pigs
Citation