Wild pigs on the Big Island of Hawaii – friend or foe?

Wild Pigs Hawaii Tribune Herald 2020
Wailoa State Recreation Area, Hilo. Photo credit: Hawaii Tribune-Herald.

In the first months of 2020 wild pigs caused significant damage to orchards and crops at Horizon Guest House. The pigs, who live in the surrounding forest of McCandless Ranch, were in the habit of making regular raids on our property. Our gardening efforts, and attempts at protection, were left in disarray as they carved a trail of destruction.

Unfortunately, feral pigs on the Big Island of Hawaii have become a widespread problem. Wild pigs are attracted to a wide variety of food sources. On the Big Island these include crops such as macadamia nuts, bananas, avocados and pineapples. Our banana and pineapple plants were almost all destroyed over a period of months. Significant rooting damage was also done to the garden.

Wild Pig Big Island Hawaii KITV4 Island News
Photo credit: KITV4 Island News

Where did the pigs come from?

It was originally thought that the feral pigs in Hawaii were the direct descendants of those brought to the islands by Captain Cook in 1778. Captain Cook arrived with pigs, chickens and other animals. However, a 2016 study found that most of the feral pigs alive in the islands today are in fact the descendants of those introduced by Polynesians in approximately 1200 AD. [1]

That the origins of the feral pigs are not solely European will be helpful for future discussions about conservation on the islands, as well as their role in Hawaiian cultural heritage.

Wild Pigs Hawaii News Now
Photo credit: Hawaii News Now

Impact on forest ecosystems

Wild pigs also have an impact on the forest ecosystem. A study by the University of Hawai’i found that soil macroinvertebrate communities (organisms that do not have a spine but can be seen with the naked eye, such as snails and insects) remained unaffected by the presence of feral pigs in the environment.[2] However, earthworms and beetles may benefit from association with sites rooted by wild pigs.

Another study found that the absence of feral pigs over time led to increased bacterial diversity in the soil and that there was an overall increase in the ‘ecological resiliency’ of the soil.[3]

WIld Pigs Tribune Herald 2017
Corner of Komohana and Mohouli streets, Hilo. Photo credit: Tim Wright, Hawaii Tribune-Herald.

How to combat feral pigs

Pigs don’t like dogs and will tend to avoid an area if they sense or smell their presence. Culling the invading pigs is also another option, but in the case of Horizon this won’t stop the arrival of more pigs as they breed at such a rapid rate in the adjoining forest. The feral pigs are resourceful and have found creative ways of digging under the boundary fence in order to gain access.

Horizon Guest House Garden
Horizon's new garden fence

Instead we decided on a new approach. We fenced a section of the garden off completely. This area, currently housing the existing vegetable garden, will now also be where we grow the crops most vulnerable to pig invasion. New banana and pineapple plants have been planted and the existing vegetable garden has been expanded. The fence itself has been engineered to be as pig-proof as possible. Additional fence posts have been positioned close together to ensure that the fence is as tight as possible and therefore difficult for even the tiniest of pigs to burrow under.

Feral pigs might appear to be cute and relatively harmless but they continue to cause problems on the Big Island as their numbers in populated rural areas continue to rise. Creative solutions are the best way to try to mitigate their impact on a local level, while perhaps a concerted effort on a state level is needed to combat the issue further.

References

Linderholm A., Spencer D., Battista V., Frantz L., Barnett R., Fleischer R.C., James H.F., Duffy D., Sparks J.P., Clements D.R., Andersson L., Dobney K., Leonard J.A. & Larson G. (2016). [1] A novel MC1R allele for black coat colour reveals the Polynesian ancestry and hybridization patterns of Hawaiian feral pigs. R. Soc. open sci. 3, 160304. https://doi.org/10.1098/rsos.160304

Wehr, N.H., Kinney, K.M., Nguyen, N.H., Giardina, C.P. & Litton, C.M. (2019). [3] Changes in soil bacterial community diversity following the removal of invasive feral pigs from a Hawaiian tropical montane wet forest. Sci Rep 9, 14681. https://doi.org/10.1038/s41598-019-48922-7

Wehr, N.H., Litton, C.M., Lincoln, N.K. & Hess, Steven C. (2020). [2] Relationships between soil macroinvertebrates and nonnative feral pigs (Sus scrofa) in Hawaiian tropical montane wet forests . Biol Invasions 22, 577–586. https://doi.org/10.1007/s10530-019-02117-3

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Koa: The Big Island’s Magnificent Wood

Koa Pig Board Horizon Guest House Hawai
Pig board showing example of 'compression or fire' very rare even for curly koa

To the casual visitor, Hawaii is sunshine and beaches. But it’s more than that. If you visit often, or for long enough, or are lucky enough to live here, you’ll discover a unique product that is grown only in Hawaii (endemic) – and no, it’s not taro, lilikoi, or even lychee: it’s Acacia koa, simply known here as koa.

Koa stand Horizon BnB Kona Coast Hawaii
Plant stand by Russ Johnson

In ancient times, it was so prized that it was made kapu, prohibited for anyone to possess except for the royal class (ali’i), by King Kamehameha in the late 1700’s. Upon his death, the kapu was removed, which allowed all Hawaiians to possess this unique wood.

Koa bowl 2 Horizon Guest House Hawaii Big Island
Classic Hawaii bowl or umeke

Similar to black walnut and known for its hardness and extraordinary beauty, the Hawaiians found a wide range of uses for koa, from canoes to household dishes and utensils. When malihini settlers arrived, they discovered that it is also a ‘tonewood’ and could be used to make stringed instruments, such as the ukulele.

Koa Pen Horizon Guest House Hawaii Big Island
Curly koa ball point pen

Koa trees can attain a height of 50-75 feet and a trunk circumference of 20 feet. They are one of the fastest-growing Hawaiian trees, capable of reaching 20-30 feet in five years.

Koa wood Horizon B&B Hawaii
Detail of fine-grained koa

Ideally adapted to volcanic conditions, the larger Hawaiian islands supported huge forests of magnificent koa trees. However, the introduction of cattle, and the resulting clearance of huge swaths for pastures, severely reduced it’s habitat.

Koa trees are not endangered and recent restrictions on cutting, and protecting the seedlings from grazing cattle, sheep, and goats, have increased its population.

BUT! The only koa that can be harvested are dead or decaying koa trees on public lands.

Koa wood Horizon Guest House Hawaii
Headboard, part of 4-poster bed patterned from King Kamehameha’s bed

It can take more than 25 years before a seedling grows into a tree large enough to be useful. In the meantime, it’s a premium wood selling for as much as $150/board. A fine piece of koa furniture, such as a dining table will set you back as much as a small car. There are several galleries on the Big Island that showcase koa pieces, Hawaii Treasure Mill and Harbor Gallery among others.

Quilt koa Horizon Guest House Hawaii Big Island
Quilted bedspread in koa leaf pattern by Sig Zane

McCandless Ranch

I’ve been lucky enough to have lived on the Big Island for years surrounded by McCandless Ranch. Their preservation techniques, practiced over many decades, have resulted in some of the best stands of koa in the state. The trees are stately and beautiful, and the wood from this island is particularly dark and red. The rarest is called ‘curly’, named for its swirly grain patterns. Curly koa is found in only 1% of koa trees.

Koa bowl Horizon Guest House Kona Coast Hawaii
Curly Koa

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Author: Angus Meek