HILO, Hawai'i — A Waipi'o Valley taro farmer shot and killed four feral horses over the past two weeks to prevent the animals from damaging his crops, according to an animal control official who said the incidents underscore growing frustration among valley farmers with the last wild horse population in the state.

Morgan did not provide the farmer's name.

She said he had fenced his taro patch, but full-grown horses simply smashed through the fencing.

The animal control officers who went to investigate a report of dead horses Thursday found three full-grown animals near the farmer's crops, and saw extensive crop damage, Morgan said. The farmer in a home near the taro field acknowledged he shot the animals, she said.

State law does not provide any protection to wild horses, but does authorize landowners to protect their property from wild animals.

The farmer who shot the animals in the recent incidents is "all for helping us remove them," Morgan said.

"This is kind of a last-ditch resort for him. He certainly doesn't enjoy or get his kicks out of killing these animals.

"I'm asking for input on how we go forward. How do we protect the ones that are left? Do we pull them out and relocate them, do we do what they do with wild mustangs on the Mainland and adopt them out? What is the best method?

"Something has to be done," she added. "We can't just let this ride, because they are going to continue to damage property and people are going to continue to kill them. Whether there's 20 down there or 120, once these animals are gone, that's it, they're gone forever."

Waimea veterinarian William Bergin, who is co-authoring a book on Hawai'i horses, said there have been feral horses on the Big Island since about 1900.

The two major Big Island populations were on Mauna Kea and in Waipi'o Valley, but the last wild horses on Mauna Kea were removed by the mid-1930s because they were a nuisance for ranching operations, Bergin said.

Bergin said there is no reliable estimate of how many feral horses are left in Waipi'o Valley, but he guessed there may be as few as 40 or 50, or as many as 150.

Bergin would like to see the last wild horses preserved.

"From a history standpoint, that's part of old Hawai'i," he said.

This is the third incident of horses being killed in the valley in the past six months, including an incident two weeks ago in which a 6-month-old animal was shot by the same farmer, according to Morgan.

The Humane Society also has been getting calls from other farmers who say the horses are regularly causing crop damage on other properties, she said.

"There's no county or state office that's taking responsibility for these horses, there's no private individual taking care of these horses, so these folks down in the valley are left fending for themselves," Morgan said.

Since Waipi'o Valley remained largely in its natural state without many fences, the horses there have continued to breed.

The Hawaiian horse traditionally has been small and hardy, but a quarterhorse stallion was released into the valley some years ago, creating a new bloodline of larger and healthier feral animals, Bergin said.

There have been increasing reports of horses getting into homesteads and taro patches and causing problems, particularly in the past 15 to 20 years, he said.

"When you do get the increase and the multiplication of these animals, you do have pressure on the local community to react in frustration, and I think that's what's happening down there," he said.

Rounding up the animals would be worthwhile, Bergin said, "but it would be a real challenge.

"It would be a challenge to the greatest cowboys and wranglers that you could find because it's pretty swampy, there's rivers down there that you don't necessarily want to ford on horseback."