DOW wants to know: Where are the bighorn?
By DAVE BUCHANAN The Daily Sentinel
Wednesday, January 24, 2007
One of Colorado’s iconic big-game animals and certainly one of the most widely recognized is undergoing scrutiny from the Colorado Division of Wildlife.
The agency that adopted as its official seal a depiction of a Rocky Mountain bighorn sheep is concerned that it’s totem animal is struggling instead of flourishing in a state with no shortage of great bighorn habitat.
The challenges fronting bighorn sheep management, and a close look at the Taylor River sheep herd, will be the focus of a meeting set for 7 p.m. on Thursday at the DOW office in Gunnison at 300 W. New York.
Wildlife officials say too many of the state’s sheep flocks aren’t recruiting young at a rate that assures a healthy herd. It appears the lambs are being born but aren’t surviving past the critical first six months, said Rick Kahn, DOW terrestrial program manager.
“Our information indicates we’ve reached a point around the state where our lamb recruitment is suppressed and we’re trying to find a way to get it better,” Kahn said. “The ewes get pregnant and drop lambs and within a month or six weeks the lambs are dying, and we can’t figure out why.”
Kahn said the problem isn’t isolated to any one herd, although some herds are doing better than others.
Bighorn sheep are notoriously complex and delicate creatures, subject to many environmental factors. Dealing with die-offs is a part of sheep management, but recently die-offs are having more of a lasting effect than what is considered normal.
“Normally, you get a die-off and the some of the herds bounce back,” Kahn said. “In some of the herds they never really build back up. They do a little bounce and never reach the previous population level.”
A herd might start at 200 animals, suffer a die-off and instead of returning to 200, slowly decline, never fully recovering even though there is no obvious reason for that yearly loss of lambs.
Some biologists theorize it may have to do with nutrition, particularly a lack of certain trace elements such as selenium, Kahn said. Disease, particularly pasteurella and the resulting pneumonia, remains a constant factor.
Wild sheep, which have no natural resistance to pasteurella, get the disease from domestic sheep.
The DOW, the Rocky Mountain Bighorn Society and the Colorado Wool Growers Association have worked together on minimizing contact between wild and domestic sheep.
“Chronic low lamb recruitment is a really hard problem to isolate,” Kahn said. “The problem could be drought, competition or habitat loss, but in the background there is the disease issue chugging along.”
He said a conference call Monday among the various DOW biologists around that state was aimed a developing a master plan to coordinate studies and gather ideas on breaking the low-recruitment cycle.
A recent estimate put the state’s bighorn population around 7,000 to 7,500 animals, Kahn said.
Historically, the state might have supported as many as 30,000 Rocky Mountain and desert bighorn sheep.
Dave Buchanan can be reached via e-mail at email@example.com.
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