Dietary niche variation in an invasive omnivore: the effects of habitat
and anthropogenic inputs on feral pig (Sus scrofa) resource use
Abstract
Invasive omnivores may have profound impacts on ecological communities
through diet selection, particularly when their functional roles differ
from those in their native range. While the threat of feral pigs (Sus
scrofa) to native plant communities in Hawai‘i are well known, their
trophic dynamics and the drivers of variation in their diet remain
understudied. We investigated the feral pig dietary niche on Hawai‘i
Island using stable isotopes (13C and 15N) and Bayesian mixing models to
identify drivers of variation in resource use. We also chronologically
reconstructed diets for six subsampled individuals to understand
temporal variation in resource use and individual diet specialization.
Our results revealed feral pigs on Hawai‘i Island exhibit a broad
dietary niche characterized by diverse diets, with substantial overlap
in resource use across districts and habitats. Differences in dietary
composition in the transition from forest to open habitat were driven
primarily by an increasing reliance on human food subsidies in
conjunction with a decreasing reliance on invertebrates, which may be
partially driven by protein constraints on dietary composition. Pigs in
forested areas largely displayed generalist feeding strategies, while
those in open habitat tended to specialize, particularly on human food
resources. Diets for chronologically subsampled individuals varied
little, suggesting feral pig resource-use strategies in Hawai‘i tend to
be stable through time. Individual niche-width was relatively narrow
compared to that of feral pigs in Hawai‘i at large, indicating the
relatively wide feral pig dietary niche is characterized by substantial
intraspecific diet specialization, likely as a result of strong
intraspecific competition. Understanding the drivers of feral pig
resource use is crucial for informing management strategies aimed at
mitigating their ecological impacts in imperiled systems like Hawai‘i.