Feral Hogs Crossed the Ocean and Are Infesting This Tropical State

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Hawaiian hogs are built different. As one of the oldest non-native animal species on the islands, they’ve weathered civilizations rising and falling, only to emerge healthier, more robust, and pervasive. Descended from both Polynesian pigs and European breeds, Hawaiian feral hogs are found throughout the islands. Their presence is a constant in the Aloha State, and it has become an increasingly serious problem.

Hawaii is home to an estimated 400,000 feral hogs, accounting for about 4% to 7% of the U.S. total. They are widespread across the islands (save one), where they destroy ecosystems, carry disease, and make fertile breeding grounds for mosquitoes. Thanks to Hawaii’s long tradition of pig farming and hunting, they aren’t afraid of humans and can be aggressive, even unprovoked. Some strategies have been employed to curb their populations, with little effect. No matter how you look at it, Hawaii is infested with feral hogs.

Hawaiian Hog History

Feral hogs aren’t native to the Hawaiian Islands, but they’ve lived there for a long time. Researchers believe that the first human populations made forays into the islands between 500 and 700 AD. Pigs came along with them. Called Pua’a, these wild pigs served as a valuable food source for the settlers. They were allowed to roam freely to some extent, but were monitored to ensure they didn’t destroy valuable crops. The introduction of new fruits like mangos and guavas, however, caused the pig population to increase dramatically.

The arrival of the first European explorers—Captain Cook and his crew—in 1778 further increased pig populations. Pigs were already a common sight on the islands, so Cook brought over European pigs in an attempt to make the Hawaiian variants even bigger.

The pigs found on the islands today are descendants of these two groups. They have been present in Hawaii for so long, in one form or another, that these hogs are considered the oldest non-native animal species on the islands. Their presence, however, has become a problem. As an invasive species, hogs don’t live in much fear since the islands lack big enough predators. This has made them all too comfortable, allowing them to root wherever they please. Due to their voracious diets and rapid reproduction (a single family line of pigs can produce 15,000 pigs in just over five years), pigs are now considered an invasive species on all the Hawaiian islands except Lāna‘i.

Feral Hogs in Hawaii, By the Numbers

The United States has an estimated 6 to 9 million feral hogs, with Hawaii accounting for about 400,000, or roughly 4% to 7% of the total population. Thanks to their expedient breeding, hogs proliferate on the islands with ease. The average pig litter size is 7.5, with numbers reaching as high as 14 per litter. This, combined with short gestation periods (114 days), means a single Hawaiian sow can produce dozens of piglets each year.

The tradition of pig hunting and farming makes the problem all the more complicated. It’s simply a way of life in Hawaii, steeped in tradition. In 2020, the annual Hawaiian pig crop amounted to 12,000, with an average of 6 piglets per litter. In 2021, the annual Hawaiian pig crop dropped by 8.3% to 11,000, a figure that does not account for the much larger population of wild hogs on the islands.

No one is exactly sure what is causing the noticeable increase in the islands’ hog population. Some suggest climate change has brought pigs down from high elevations to urban lowlands, while others blame people feeding pigs for bringing them into developed areas. Another contributing factor is the state’s restrictive hunting laws. Much of Hawaii consists of extensive tracts of public and privately owned land. Pigs can roam relatively freely in these areas, but hunters are often restricted from accessing them.

Proliferation and Infestation

Regardless of the cause, feral hogs have moved from jungle forests and open pastures into urban areas. Plus, they don’t seem to fear humans. Although hogs are distributed across most of the major islands, their increasing numbers indicate an infestation. The word is defined as “to spread or swarm in or over in a troublesome manner.”

This suggests that the Hawaiian islands have long been infested with feral hogs, and the problem is getting worse. Even major cities like Honolulu have grown accustomed to swarms of feral hogs roaming through neighborhoods, rummaging through dumpsters, and threatening residents.

Feral hog attacks are rare, but they can be deadly. A global study noted 163 separate reports of fatal wild pig attacks between 2000 and 2019, resulting in 172 deaths worldwide. In states like Hawaii, where pigs roam freely without much fear of retribution, the risk of attack becomes even greater. That study also reported an average of 8.6 human deaths per year worldwide due to wild pig attacks. However, attacks are not the only problem; hog populations also have severe environmental consequences.

Hog Disease and Environmental Damage

Hog attacks can prove fatal, but so can the laundry list of diseases they carry. Feral pigs of any kind are known to carry diseases like E. coli, toxoplasmosis, and trichinosis. They also carry Aujeszky’s disease, or pseudorabies, which is highly infectious and fatal to many animals, including cats, dogs, and swine. All told, Hawaiian hogs act as hosts for at least 30 viral and bacterial diseases and nearly 40 parasites that can be transmitted to humans, pets, livestock, and other wildlife.

Even if Hawaiian hogs do not frequently transmit diseases to humans, they still cause serious environmental damage. Ever on the hunt for food, Hawaiian hogs routinely dig up soil. This behavior disturbs the forest floor, erodes soil, and kills native plants. Such damage is particularly evident in the Oahu dry forest. It also prevents young plants from establishing and growing properly. In addition to damaging the ecosystem, wild pig foraging creates dry brush, which can increase the risk of wildfires.

To make matters worse, Hawaiian feral hogs create conditions for mosquitoes to proliferate. While foraging, pigs often hollow out the interiors of tree ferns. These hollowed-out trees then collect rainwater, creating ideal breeding grounds for mosquitoes.

Feral Hog Containment

In Hawaii, feral pigs are managed for both recreation and subsistence. While conservation groups attempt to reduce pig populations in certain protected areas, the Hawaiian Department of Forestry and Wildlife manages pigs as a limited resource in other parts of the state.

In recent years, some strides have been made to reduce the negative environmental impact of feral hogs. The Kaua‘i Game Management Advisory Committee successfully increased native plant growth on the Alaka‘i plateau up to 35% by erecting fences. Similar efforts have helped contain feral pigs, although some residents criticize these measures as an encroachment on traditional ways of life.

Time will tell how effective these reduction efforts will be. Pigs remain a problem across the United States, but the impact is particularly severe in Hawaii. Without any natural predators and the ability to breed quickly, feral hogs will remain a problem in Hawaii for the foreseeable future.

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