Humane fertility vaccine helping to manage Idaho wild horses

March 4, 2016 -- A count of wild horses on the Challis Herd Management Area indicates that a BLM program to reduce fertility among the herd’s mares may be working, an agency representative said.

A one-day count of the horses, done by three observers in a helicopter, took place Feb. 23. Kevin Lloyd, wild horse specialist with the BLM’s Challis Field Office, said the helicopter followed flight lines half a mile apart on a pattern set by the U.S. Geological Survey.

    The Challis Herd Management Area covers about 240 square miles south of Challis, bordered on the north by the Salmon River, on the west by the East Fork of the Salmon River, on the south by a ridge between Herd Creek and Road Creek (just north of Trail Creek Road) and on the east by U.S. Highway 93.

    According to the Challis Field Office website, the wild horses near Challis originally came from livestock that miners and ranchers brought to the area around 1870.

    The website states that the BLM has determined that the area can support 185 wild horses while providing for other land uses and resource values.

    Lloyd said the previous count, done in 2014, showed there were 203 adult horses on the area. Raw data from the recent count was 225 adult horses and 15 foals. He said the raw numbers are being adjusted by a statistician at Colorado State University to take into account potential double counts and horses that were missed. He said an adjusted number should be available in a few months.

    Lloyd said the natural rate of population growth in the Challis herd is 17 percent per year; that rate of growth would produce a current count of 278 adult horses.

    “Overall, the general population is pretty healthy,” Lloyd said. “There are fewer out there than we anticipated.”

    Lloyd said the BLM has been conducting a fertility-control program on the herd since 2004. He said roundups were done that year and in 2009 and 2012, during which the BLM tried to gather 80 to 85 percent of the herd. He said all mares over 2 years old that were captured were treated with an anti-fertility vaccine called porcine zona pellucida, commonly known as PZP. The vaccine stimulates the mares’ immune systems to produce antibodies against it. The antibodies also attach to the sperm receptors on the mares’ eggs and distort their shape, thereby blocking fertilization. Lloyd said the vaccine wears off after about three years.

He said one goal of the population counts is to determine whether the fertility-control program is working.

“We’ll continue with the management process that we’ve had in the past, but it’s good to know what we have out there and what’s happening with the herd,” he said.

    Lloyd said the national wild horse program is conducting fewer roundups, and the next gather and fertility treatments on the Challis herd probably won’t occur for another few years.

    The size of the herd has been reduced substantially since 1979, when 2,119 horses were captured and 1,875 were removed and put up for adoption. According to the BLM, 13 more roundups have taken place since then. During the most recent, in 2012, 267 horses were captured and 150 were removed.

    According to a news release from the BLM, wild horses and burros that exceed a Westwide level of 26,715 are subject to removal from the range, in accordance with the Wild and Free-Roaming Horses and Burros Act of 1971. The most recent estimated wild horse and burro population, as of March 1, 2015, is 58,150, an 18 percent increase over the 2014 estimate of 49,209.  That means the current Westwide population exceeds the appropriate management level by 31,435.

    The roundups have been controversial, with opponents claiming they’re done mainly to provide more forage on public land for cattle and sheep.

    Currently, more than 47,000 off-range horses and burros are fed and cared for in either off-range corrals or off-range pastures at a cost of $49 million a year, which accounts for 65 percent of the BLM’s Wild Horse and Burro Program budget.

    “The ability to place horses in good homes has slowed down,” Lloyd said.

    An untrained animal generally costs $125. Each horse or burro placed into private care saves taxpayers nearly $50,000, the BLM stated.        

    An adoption event will be held in Nampa on April 17, at the Idaho Horse Expo, Ford Idaho Horse Park, 16200 Idaho Center Blvd.

Originally published by the Idaho Mountain Express, March 4, 2016.

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