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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Springtime gardening on the Big Island

Spring is the perfect time to get organised with the vegetable garden here on the Big Island. We’ve turned the vegetable and herb gardens into special lockdown projects (no doubt like many of you) and have spent the last couple of weeks prepping the gardens for planting, raising and transplanting seedlings, and protecting our new plantings from outside invaders! (namely slugs…)

(Check back for updates! We’ll be updating this post as the garden grows. Click the links below to see our progress!)

Snap peas

We’ve grown snap peas in the past and they are always a delicious addition to the garden. First we started out by growing the seeds in individual pots, then we transplanted them to the garden beds. Peas were easily the quickest to grow from seed and grew noticeably every couple of days.

Before and after

It had been a while since we’d last grown peas and the garden bed was looking a little sad! It was time remove the weeds, pull out the wire frames and start again from scratch.

Then it was time to transplant. We managed to get four viable pea plants grown from seed. However, we lost two of these a couple of nights after planting due to an attack of slugs… 

Peas trellis 13:5 Horizon Guest House Big Island
Progress update May 13th

Lettuces, arugula, beets and radishes

Lettuces Big Island Gardening

We wanted to make sure we had a good variety in this garden so planted out lettuces, beets, arugula, radishes and spinach.

Lettuces Horizon B&B

Lettuces were slow to come through but finally the baby lettuces appeared!

Lettuce4 Horizon B&B Kona

Radishes quickly flourished from seed and most of what we planted grew. It wasn’t the same for the beets (only two grew from seed, bottom right in the photo) and only a couple of spinach plants came up (top left in the photo).

Progress updates:

Radishes 9:5 Horizon B&B Big Island
Lettuces/Radishes May 9th
Lettuce bed Horizon B&B Big Island 9:5
Lettuces/Radishes May 9th
Radishes 13:5 Horizon B&B Big Island Hawaii
Radishes May 13th
Beets 9:5 Horizon Guest House Big Island
Beets May 13th
Lettuces 22.5 Horizon BnB
Lettuces/Radishes May 22nd
Tomatillos 22.5 Horizon BnB
Tomatillos May 22nd

Herbs

Garden herbs Big Island Horizon

It was trial and error with the herb garden. Initially we planted basil, thyme and cilantro from seed but after 10 days… nothing appeared. We decided the fault was the age of the seeds (pro tip: if the seeds look like they’re ancient then they probably are and they probably won’t work). For our second attempt we decided to plant a mixture of seeds and small plants, just to give ourselves a head start. 

Herbs Horizon HGH

Basil, dill, cilantro, thyme and spearmint plants were planted, as well as seeds of dark basil, thyme, cilantro and sweet basil in the hope that the combination would yield some lasting results. But then disaster struck again! The same night the slugs made their appearance and decimated the transplanted peas they also launched an assault on our thyme and cilantro. We used citric acid to kill the slugs but in the process also terminally damaged the thyme and cilantro…

What is dark basil?

Dark opal basil is a basil variety created at the University of Connecticut in the 1950s. It has dark purple leaves and a stronger flavour than sweet basil.

Herbs 2 HGH Kona

Third time lucky! This time we replaced the damaged thyme and cilantro and used slug bait to form a defensive perimeter! This seems to have stopped the slugs for now.

Herbs Horizon Big Island

Progress updates:

Dark Basil 9:5 seedlings Horizon B&B
Dark Basil May 9th
Cilantro 9:5 Horizon B&B Big Island Hawaii
Cilantro May 9th
Cilantro 13:5 Horion B&B Big Island
Cilantro May 13th
Sweet Basil 22.5 Horizon Guest House Hawaii
Sweet Basil May 22nd

Pineapples

Pineapples B&B Horizon Guest House

We transplanted some smaller pineapple plants from another area of the property to this garden. In order to suppress weeds we had already covered unused beds with a ground cover. By slicing a series of cuts into the cover we were able to plant a row of pineapples and also continue to stop the weeds from returning.

Seedlings

We were also quite successful growing okra, peppers, tomatillo, yellow tomatillo and roma tomato seedlings. We started the seeds off in recycled fruit containers and then moved them to peat pots.

Seedlings Horizon B&B Kona
Step 1
Seedlings2 Horizon B&B Kona
Step 2
Seedlings Horizon B&B
Step 3

Moving the seedlings to peat pots was a delicate operation, especially for the okra and roma seedlings. They had to be carefully moved, and any roots untangled before planting.

Transplanting

And finally the seedlings were planted in the garden. Followed by a good watering and a measure of liquid fertilizer to help them on their way!

Seedlings Horizon Guest House
Transplant 2 Horizon B&b
Roma tomatoes

Progress updates:

Lima Beans 9:5 Horizon B&B Hawaii
Lima Beans May 9th
Lima Beans 22.5 Horizon Guest House
Lima Beans May 22nd
We’ll keep you updated on the garden as it (hopefully) flourishes! Have you found yourself in the vegetable garden more during the lockdown? What have you been planting?

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