UH Studies Examine Impacts of Feral Pigs

November 16, 2019, 8:06 AM HST
* Updated November 16, 8:08 AM
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NREM MS students Dain Christensen and Nathaniel Wehr. UH courtesy photo.

In an effort to maintain Hawai‘i’s delicate forest ecosystems, researchers from the University of Hawai‘i at Mānoa have completed two studies examining the impacts of feral pigs on soil bacteria and insects in specific habitat areas.

Nathaniel Wehr, Creighton Litton, Christian Giardina, Steven Hess, Noa Lincoln and Nhu Nguyen researched a series of ecological sites where feral pigs have been removed in Hawai‘i Volcanoes National Park and Pu‘u Maka‘ala Natural Area Reserve.

Published in Nature Scientific Reports, the first study examined changes in bacteria communities in wet forests after feral pigs were removed and found that bacterial diversity improved, though their functional diversity remained the same. The study concluded that these changes promoted the ecological resiliency of the soil.

The second study examined the relationship between macroinvertrebates (like worms, ground beetles and nematodes) with feral pigs. Published in Biological Invasions, the study found that macroinvertebrate communities in the soil did not change after feral pigs were removed. However, earthworms and ground beetles were positively associated with sites impacted by feral pigs.

Split image of untouched area versus area impacted by feral pigs. UH courtesy photo.

The researchers hypothesized that pigs improve earthworm habitats by mixing organic matter and reducing the density of wetland forests. They also theorized that pigs are capable of finding soils with more below-ground food sources.


A UH Mānoa news release stated said the removal of feral pigs is an important part of managing Hawai‘i’s forests considering the critical role soil microfauna and mesofauna play in forest ecosystems. Both studies will help inform the management of Hawai‘i forests regarding feral pigs, and balance eradication efforts with the desire to maintain them for cultural and recreational purposes.

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