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Leveraging multiple data sources to assess competition between introduced wild pigs and native deer

Parsons, Mitchell1; Young, Julie1

Published Oct 01, 2025 on Dryad. https://doi.org/10.5061/dryad.dz08kps9b

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Abstract

Introduced species have diverse impacts on native wildlife and ecosystems. Negative effects of introduced species on native species through competition or amensalism are frequently hypothesized, but challenging to test in the field, particularly for large vertebrates. Wild pigs (Sus scrofa) are a widely distributed introduced species that are hypothesized to compete with native wildlife. We used multiple data sources to evaluate the strength of negative effects of wild pigs on native black-tailed deer (Odocoileus hemionus columbianus) by looking at multiple niche dimensions and fitness consequences for deer. We combined isotopic niche data with camera surveys that provided density, spatial overlap, and temporal overlap of deer and wild pigs. We also used cameras to gather data on deer body condition and reproduction to use as fitness metrics. We evaluated niche overlap between deer and wild pigs and evaluated if deer fitness was related to the density of wild pigs. Our results illustrate overlap in space, time, and isotopic niche between wild pigs and deer. Despite this overlap, we observed no relationship between wild pig density and deer body condition or reproduction, suggesting minimal effects of competition or amensalism on deer. Our results confirm the resource overlap that has been observed between deer and wild pigs in other systems, but contradict the perception that wild pigs are negatively affecting deer through resource competition. We demonstrate that the effects of wild pigs on deer may be weaker than has previously been thought, depending on the resource availability. Our approach also provides a framework for going beyond measuring niche overlap to provide a more thorough understanding of competition between large vertebrates in a field setting.