Wild boars, also known as feral pigs or pua’a, are found across the Hawaiian Islands. Not native, they were introduced centuries ago. Their presence has led to significant impacts on the islands’ natural environments and agricultural lands, posing ongoing challenges for conservation and land management.
Arrival and Traits
Wild boars first arrived in Hawaii with Polynesian voyagers between 500 and 700 A.D., brought as a food source. These early pigs were smaller and managed by humans, often kept in designated areas to prevent damage to crops like taro and sweet potatoes. The modern wild boar population is a result of these Polynesian introductions mixing with European breeds brought by Captain Cook in 1778, who aimed to increase pig size.
Today’s Hawaiian wild boars are hybrids, with coarse, bristly hair that can be black, dark brown, or grey. They weigh between 100 to over 200 pounds, possessing a long snout, short ears, and, in males, curved tusks. Females can have two litters annually, each averaging around 7.5 piglets, after a gestation period of about 114 days. This rapid reproduction has contributed to their estimated population of 400,000 across the islands, excluding Lana’i, where they are no longer found. They inhabit diverse environments but are commonly found in wet forests and open mountain pastures.
Environmental and Agricultural Consequences
The presence of wild boars in Hawaii has substantial negative consequences for both native ecosystems and agricultural sectors. Their rooting behavior, where they dig for roots, tubers, and insects, severely disrupts the forest floor, uprooting native plants and altering soil structure. This activity leads to soil erosion and compaction, hindering new plant growth and causing sediment runoff that damages sensitive coral reefs. Over 40% of the land in some areas shows evidence of pig rooting.
Wild boars also contribute to the spread of invasive plant species by consuming their seeds and dispersing them through their digestive tracts, or by carrying them on their fur. This allows non-native plants, such as strawberry guava, to outcompete and smother native vegetation. Their wallowing habits and the hollowing out of tree ferns create depressions that collect rainwater, forming ideal breeding grounds for mosquitoes. These mosquitoes transmit avian malaria, a disease threatening Hawaii’s native forest birds, including endangered honeycreepers. Boars also prey directly on ground-nesting birds and their chicks.
Beyond their ecological impacts, wild boars cause considerable damage to agricultural operations. They destroy crops such as taro, sweet potatoes, macadamia nuts, bananas, avocados, and pineapples, often decimating entire fields overnight. This destruction extends to infrastructure, including fences and park grounds, leading to costly repairs for farmers and local communities. The financial burden of these damages is a persistent issue for land managers.
Control Measures
Managing wild boar populations in Hawaii involves a range of strategies, often implemented by government agencies, conservation groups, and private landowners. Hunting is a common method, permitted year-round on private land with permission, and during specific seasons in public hunting areas. Hunters must possess a valid hunting license and can use various weapons, including rifles, archery equipment, muzzleloaders, knives, and spears, sometimes with dogs. Some special hunts may have no bag limits, emphasizing population control.
Trapping is another widely used and effective control measure, particularly with large corral traps designed to capture multiple animals. Modern trapping techniques incorporate remote triggers and specialized net traps, improving efficiency in challenging terrain. Once captured, pigs are handled according to local regulations, which may involve humane euthanasia or relocation.
Fencing and barriers are frequently employed to protect vulnerable areas like agricultural fields or sensitive ecological sites. These fences must be robust, tall, and buried deep to prevent the animals from burrowing underneath. Electric fencing also provides a deterrent. Habitat modification, such as removing accessible food sources, can make an area less appealing to wild boars.
Community engagement and education are important components, raising awareness and coordinating efforts among residents. Ongoing research and monitoring of boar populations and their movements contribute to developing more effective and adaptive management plans. Historically, large-scale eradication projects have occurred, including one from 1900-1958 that removed 170,000 pigs. Conservation organizations continue to employ professional hunting teams for population reduction.