Impacts of wild pigs on acorn availability as a food source for native wildlife

Abstract

Context Wild pigs (Sus scrofa) are a non-native invasive species that causes millions of dollars in damage each year to agriculture in the United States of America, destroys native plant communities, and competes with native wildlife for seasonally available pulse resources such as acorns. Despite many anecdotal observations and diet studies suggesting wild pigs reduce acorn availability for other wildlife species, no studies have comparatively examined acorn consumption among species in a natural environment (i.e. competition). Aims Our objective was to estimate the consumption of acorns by wild pigs relative to that of other native wildlife species. Methods We established 40 monitoring stations beneath acorn-producing trees in a 3406-ha study area in eastern Alabama with an approximate density of 9 pigs/km2. At each monitoring station, we placed five acorns on a 1-m × 1-m sand pad and positioned a game camera to record acorn fate during 2-week intervals once a month from September to February 2018–2019 and 2019–2020. Cameras were set to capture images once every minute continuously during the survey period. Additionally, we constructed acorn traps from 18.9-L plastic buckets to estimate the timing and relative amounts of acorns that were potentially available for consumption at each monitoring station. Key results From approximately 7.3 million camera images, we observed 15 wildlife species consuming 707 acorns over the 2 years. Aside from animal consumption, acorn fate was categorised as lost due to flooding (n = 153), remaining on the sand pad at time of camera failure (n = 720), or not consumed during the sampling period (n = 536). Key conclusions Top acorn consumers were squirrel (Sciurus spp.), white-tailed deer (Odocoileus virginianus), raccoon (Procyon lotor), and wild pig. In the 2018–2019 sampling period, wild pigs consumption accounted for 23.4% (n = 87) of the total consumed acorns. After wild pig removal efforts were initiated in the summer and autumn of 2019, wild pigs consumed only 7.2% (n = 24) of consumed acorns. Implications Wild pigs consume a significant number of acorns and likely reduce the availability of this pulse resource for other native wildlife species and may potentially influence oak regeneration.