Back on the range: Bighorn sheep get some help to survive on the Stansbury

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Big-game wildlife transplants are risky, costly and uncertain. Some animals try to find their way home, others settle into their new digs and a few get eaten.

In the winter of 2005, state wildlife officials began a series of transplants that eventually would move 93 Rocky Mountain bighorn sheep from Antelope Island on the Great Salt Lake to the Stansbury Mountains in Tooele County. The move was initiated to reduce an ever-growing herd on the island and create a new population for wildlife viewing and for hunters, who pay big bucks for the experience. In February, a hunter paid $110,000 for a permit to hunt a Rocky Mountain bighorn sheep in Utah this year.

Before the sheep were released in the Stansburys, each was fitted with a radio collar.

At the same time, research biologists from Utah State University were involved in the challenging task of capturing as many mountain lions on the range as they could. Five lions were caught, tranquilized and also fitted with radio collars.

This set up a unique, and controversial to some, three-year research project by the Utah Division of Wildlife Resources documenting how quickly large predators turn their attention to a new food source and how large mammals like bighorn adapt to a new range.

"Mountain lions eat sheep and a healthy population can overcome that, but lion predation can affect a population that is just getting started or is distressed due to disease," said Anis Aoude, big-game mammal coordinator for the DWR.

To help the transplanted bighorn become established, state biologists decided to kill any cougars that developed a taste for wild sheep. The protocol included removing any mountain lion that killed two sheep within a 30-day span or three in one year.

"The first three [bighorn] were killed within two weeks by the same lion," said David Stoner, a graduate research assistant at USU who oversaw the mountain lion portion of the project. "He was dispatched. The next cougar kill was in the spring of 2008."

That lion preyed on two bighorn. A third lion killed a bighorn in November 2008, but DWR officials are not sure why that animal was killed, as it appears to have preyed on only one sheep.

"To the best of my knowledge, the protocol was followed," said Kevin Bunnell, mammals program coordinator for the DWR. "It may have been a decision of pattern and history."

During the three-year project, a total of 12 bighorn died, counting the six killed by cougars.

Kirk Robinson, director of the Utah-based Western Wildlife Conservancy, appreciates that research was done before lions were killed, but says killing a cougar that is just trying to survive isn't right.

"I understand that they wanted to give the bighorn [herd] a good chance for making it, but just because a mountain lion eats wild sheep doesn't mean we should kill it," he said. "We shouldn't kill it just for being a mountain lion."

Mountain lion hunting is allowed on the Stansburys (the statewide cougar season begins Nov. 18), but researchers said cougar hunters are rarely seen there due to rough and steep terrain and difficult access to the range.

Olson and Aoude say the relocated herd is doing well, as well as any other in the state, in fact.

"Survival of females and their offspring drives population growth," said Daniel Olson, who began tracking the bighorn and their habitat while a graduate student at Brigham Young University and is now at USU. "We have monitored survival of females at 95 percent from year to year and saw 60 to 70 percent survival on lambs."

Olson said the population is now around 150 animals.

"We continue to monitor that herd closely and there have been no recent cougar mortalities," Aoude said.

The Stansbury herd is doing so well that state biologists have proposed a limited hunt of one or two animals in 2010. If approved by the Utah Wildlife Board, it shouldn't be difficult for hunters to find the sheep.

The bighorn have not ventured far from their release site on the northern end of the Stansbury Mountains. The animals are using only a small portion of the north-to-south running range. Of the Stansburys' 700 square kilometers, Olson says the sheep used only 26 square kilometers near Interstate 80 during the study.

"They select habitat free of tree cover, areas that are open," Olson said. "It is a bighorn defense mechanism they use to avoid predators. They use steep slopes to outmaneuver lions, and the open areas give them more time to detect the threat."

There were no bighorn sheep on the Stansburys when the transplants from Antelope Island arrived. Mountain lions on the range had previously soothed their hunger pangs predominantly with mule deer.

Biologists say mule deer do not frequent the northern end of the Stansburys and, therefore, mountain lions rarely use the area.

"There are not many mountain lions out there. We covered the mountain pretty thoroughly and ultimately only collared five animals over the course of three years," Stoner said. "It is interesting that all the animals removed for killing bighorn were males. By their nature they are constantly surveying the land looking for females or intruders. In that first case, the male was probably just going through and he stumbled into this new food source."

While the first two lions fit the protocol for taking out a predator feeding on the bighorn, the third did not. That bothers Robinson.

"They should stick to protocol, and it seems like that was violated," Robinson said. "It is important to maintain public trust."

Robinson suspects there was pressure from hunting groups to kill the third lion because it had preyed on a large bighorn ram, a potential trophy. The project's cost, roughly $45,000 a year, was covered mostly by the state's conservation permit program. Various hunting groups also contributed money.

The conservation permit program auctions hunting tags to the highest bidder, with the money going back into programs for specific species.

Aoude said the state will continue to track the Stansbury bighorn that already have collars, but biologists won't collar any more animals.

And lions that feast too frequently on bighorn for the state's liking will continue to be killed.

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