CHEYENNE -- Portable electric fences as night pens for domestic sheep in the Upper Green River region of the Wind River Mountains last summer protected sheep and sheepherders from predatory animals, according to a rancher.
Speaking before the Wyoming Animal Damage Management Board last week in Cheyenne, rancher Mary Thoman also said the pens reduced the number of grizzly bears removed from the area because of conflict.
Although the electric fences were originally designed to hold chickens, the board provided $14,000 for W&M Thoman Ranches to purchase the portable night pens and other devices aimed at deterring predators from attacking sheep and herders.
"The project was a success," Thoman said. "The pens let the sheep rest at night. It meant a lot, as we could see in their weight gains."
Thoman said her family's 4-month-old lambs came off the mountain at a record average weight of 96 pounds. She said the herds were calm after resting all night instead of running from predators, as had been the case the past few years with increased grizzly and wolf populations on the allotments.
The Thoman family has grazed four allotments in the Elk Ridge Complex in the Upper Green River region for 34 years. The ranch places three herds of about 1,000 head of sheep on the allotments for grazing from July through September each year, leaving one allotment to rest annually.
One of the allotments was frequented by 12 grizzlies and four black bears this year, and two black bears were removed by wildlife managers in response to depredations, Thoman said.
A second herd was harassed by two grizzly sows and their cubs, and two wolves, with one grizzly bear removed by state officials.
A third herd was frequented by two or three grizzlies, six wolves and a mountain lion all summer.
While the sheep were safe at night, Thoman said the predators were successful in preying on the herds in daylight.
"The major killing occurred during the daytime when small groups of sheep were run up into the timber or rocks and then killed," she said.
State and federal wildlife managers and animal damage experts were on the scene to help minimize livestock losses and document problems, but losses to predators were substantial again this year, Thoman said. She added that the losses would have been "astronomical" without the use of the night pens.
In the past year, predators killed 259 ewes and 186 lambs, with a total value of about $65,000. The Thomans received nearly $54,000 in damage compensation from the Wyoming Game and Fish Department, with the ranch forced to absorb the remaining $11,000 in losses on its own, she said.
Livestock losses to predators on the allotments have increased steadily in recent years, with damage ranging from about $17,000 in 2005 to $40,000 in 2008 to $65,000 in 2010.
Thoman said that while the ranch had made adjustments to try to control losses, the arrival of female grizzlies with cubs resulted in a doubling of livestock losses.
One night in late September, a female grizzly and her cub attempted to dig underneath the electric fence to get to the sheep inside, but failed. Thoman showed the board photos and videos of the trench left by the bears.
"With the nightly use of pens, the herders were able to secure the three herds at night and did not have to jeopardize their lives to check on sheep that may have been attacked by bears or wolves," Thoman said.
One of the Thomans' sheepherders was mauled by a grizzly bear during the 2009 grazing season when he stepped away from his tent to check on a barking livestock protection dog.
While the night pens were deemed successful, not all deterrents worked as well. Herders on one allotment used a large spotlight on the back of their tent to discourage grizzlies, while another used a small electric pen around his tent. Herders using an air horn to scare bears found it worked to deter black bears, but attracted the curiosity of grizzlies. Flashlights were no deterrent at all. Herders had to be moved out of their tents and into sheep wagons until electric pens could be set around their campsites once a grizzly threatened to enter, Thoman said.
On another occasion, a sow grizzly and her cub became entangled in an electric fence around a herd, then gained entrance and killed about 20 sheep.
"This bear may acclimate to swatting the pen, as this was the second attempt she made at entering the pen," Thoman said.
The Thomans use a variety of deterrents, from a half-dozen livestock protection dogs with each herd, to bear-proof containers for food and supplies storage. Thoman ranch herders do not carry firearms, but are supplied with pepper spray. The herders receive training in safety and in food storage requirements.
The Thomans use livestock protection dogs that have proven to be effective against male grizzlies, but have limited effectiveness with bear family groups, and with wolves. Wolves killed four of the Thomans' guardian dogs in 2004.