Long-term monitoring of feral hog (Sus scrofa) disturbance in seepage slope wetlands

Background/Question/Methods

Florida is home to one of North America's most unique and diverse natural ecosystems, the seepage slope. Unusual hydrology and frequent fires have resulted in a habitat that supports a variety of carnivorous plants. Feral hog (Sus scrofa) foraging has resulted in soil disturbances in seepage slopes on Eglin Air Force Base (EAFB). Rooting is a serious threat to this community because it can degrade primary processes, set back succession, and cause changes in species composition and plant population structure. These changes are important because these wetlands provide increasingly rare habitat for several threatened and endangered species. The USDA APHIS Wildlife Services trap hogs on EAFB in an attempt to reduce hog disturbance in the seepage slopes. This ten year study on EAFB investigates if: 1) there is a trend in the amount of hog disturbance and what is driving this trend; 2) hogs selectively forage in certain portions of the seepage slopes; and 3) there have been shifts in dominant functional groups. Foliar cover of total vegetation, forbs, grasses, woody species, and Aristida stricta was estimated in plots stratified by position on slope. Presence of hog disturbance was also recorded and analyzed for correlation with local rainfall data. 

Results/Conclusions

No long-term linear trend was observed in feral hog disturbance. There was no significant change in the number of disturbed plots from 2002 to 2010, although a decline in 2012 was significant. We also observed feral hogs preferentially rooting in the lower, wetter zone of seepage slopes.  Foliar cover of forbs and grasses did not change significantly during this ten year time period. However, A. stricta cover declined significantly while woody cover increased. 

Longer trend data is needed in order to determine changes in and drivers of hog disturbance due to the observed annual variation in percent of disturbed plots. Protection of the lower, wetter portions of the seepage slopes should be a management priority due to the implications of continued hog disturbance on the persistence of rare, endemic plants and animals found in this area. The decline in A. stricta cover is concerning because this dominant matrix grass acts as a fine fuel source to carry fire in this system. This decline in the cover of fine fuels has implications for fire management and continued woody encroachment. Research such as this can be used to direct future management activities to better protect this rare wetland community.