The most recent sighting prompted federal and state wildlife and agricultural officials to visit Fremont Island on Tuesday and kill 10 of the feral pigs.
"It is possible there are still more. We will be making other trips to the island to see if any remain and will remove them if there are," said Warren Hess, assistant state veterinarian for the Utah Department of Agriculture and Food's Division of Animal Industry. He was joined by staff from the U.S. Department of Agriculture's Utah office of Wildlife Damage Management in the aerial and land hunt on Fremont Island.
Hess said there are two major causes for concern when it comes to feral pigs.
"They could expose any domestic populations to disease. We have a huge swine production facility outside of Milford that would be severely impacted if disease got there," Hess said. "These Eurasian-type boars are extremely adept at survival in the wild and they are extremely destructive to the land. This is the reason the Legislature put a ban on hunting them. We just can't afford to have them running wild."
The 2012 Utah Legislature passed a bill that made it illegal to release swine on public or private property for hunting purposes. Hess said it is also illegal to import and to hunt Russian boars or other Eurasian pigs.
The situation on Fremont Island came to light in February 2010, when one pig, believed to be from wild Russian stock, was chased by wildlife officers on the causeway and ended up drowning. The incident led to an investigation of Fremont Island, where troubling numbers of feral pigs and exotic sheep were spotted. The pigs and sheep had been released there by a group Barrow Land and Livestock leasing Fremont Island from the owners. At least one hunt for both species was held on the island.
Hess said they have been working with the owners of Fremont Island Island Properties for three years. The owners have been helpful, but the removal of the pigs became complicated when Barrow Land and Livestock defaulted on lease payments.
The Barrows eventually were evicted in a case settled in December 2011. The Barrows agreed to pay $40,000 to Island Properties and leave behind pigs, sheep, chukars and one cow, according to documents filed in 2nd District Court in Ogden.
However, the Barrows defaulted on $30,000 of that agreement, according to a debt-collection lawsuit Island Properties filed against the family the next year. Judge Noel Hyde ordered the Barrows to pay the money, plus an extra $3,193.65 in interest and court costs.
Hess said state and federal officials were ready to remove the swine at any time, but the island owners elected to hire someone to perform the task. According to a report from the man hired to remove the pigs, he killed 55 in September and thought maybe there were 10 left on the island. He planned to return to Fremont when he had access to a helicopter again.
But the report of the pig on Oct. 12 spurred Hess into action, with the permission of the owners.
So the pigs of Fremont Island may have been eliminated, but the sheep remain.
Hess said they have been left at the request of the owners, but he noticed a steep decline in the sheep population. After seeing "several hundred" on his first flight over the island three years ago, Hess spotted just over a dozen Tuesday.
"I suspect the pigs have been eating the sheep," he said. "They will definitely eat ones that have died and I suspect that if the pigs had a chance, they would go after the young ones and, if enough of them went together, maybe even an adult."
With the pigs gone, the number of sheep could rebound. Even though the sheep assumed to be a mongrel mix of exotic species have never been spotted trying to leave the island, it still concerns state wildlife biologists.
"If the sheep did find a way to Antelope Island, they could mix with bison and our California bighorn sheep," said Leslie McFarlane, wildlife disease coordinator for the Utah Division of Wildlife Resources. "Certain types of viruses can be passed to the bison and it could kill the bighorns."
Tribune reporter Nate Carlisle contributed to this story.