An already "robust" population of mountain lions in the Catalina Mountains appears to be increasing - and that could pose a threat to a planned reintroduction of bighorn sheep in the range this fall.
Lions, which sometimes prey on bighorns, might hinder or even derail an effort to rebuild a herd in the Catalinas.
In response, state wildlife officials have approved a plan for what they call the "administrative removal" - or killing - of lions that kill sheep.
"This would be done in a very limited, conservative way," said Mark Hart, spokesman for the Arizona Game and Fish Department. "If we determine that a particular lion is killing sheep, and if we can find it, then it will be removed. But it would be a very tightly controlled process."
Game and Fish officials last month confirmed their plan to move 30 bighorns from a healthy herd near Yuma to the Pusch Ridge Wilderness in the Catalinas, north of Tucson, in November. Additional transplants in the following two years would bring the total to about 100 animals.
It's an effort to re-establish a once-flourishing herd that died out in the late 1990s.
Possible reasons for the herd's demise, according to wildlife officers, include urban encroachment, human disturbance, disease, fire suppression - and predation by mountain lions.
That lion threat could increase because the population of the big cats is apparently on the rise.
The population - estimated very generally at 60 to 70 lions in the Catalina and nearby Rincon Mountain areas - is "robust, and there's a pretty strong indication that the population is going up," said Jim Heffelfinger, regional game specialist for the Game and Fish Department.
He said it's difficult to accurately survey the lion population because the animals are secretive, stealthy and hard to see. But other indicators - including frequent lion sightings in Sabino Canyon, and increasing numbers of lions killed by hunters in recent years - point to a rising population.
Concern over the lion threat prompted the department to consult with several environmental and wildlife groups and the U.S. Forest Service to draw up a plan for dealing with the powerful predators.
Called the "Santa Catalina Adaptive Mountain Lion Management Plan," the document calls for the killing of "specific individual mountain lions which prey on bighorn sheep."
It does not authorize pre-emptive killing of lions in the Catalinas before sheep are moved there.
"That is not something we considered," Heffelfinger said.
FINDING KILLER LIONS
An obvious question: How will wildlife officers know they got the "right" lion - the one that killed a sheep?
Technology and data on lion behavior play key roles.
Bighorns released in the Catalinas will be fitted with global positioning system collars. The collars include a "mortality signal" that is activated after four hours of inactivity by the animal.
Using the GPS signals, wildlife officers can locate a dead sheep quickly.
This is where lion behavior plays an important role.
"When a lion kills a sheep or another big ungulate (a mammal with hoofs), the lion hangs around for 100 to 200 hours," Heffelfinger said, citing data from collared lions and other research. "They will basically bed next to the dead carcass" or nearby.
A hunter using lion-tracking dogs then might locate and kill the lion near the kill site - with reasonable assurance that it was the lion that killed the sheep.
Heffelfinger said skilled lion hunters would be hired to track the animals because the department doesn't have such hunters on staff.
It's possible, Heffelfinger noted, that there will be few rather than many problems involving predation by lions.
One reason that could be the case is that the population of white-tailed deer - prime prey for lions - has increased dramatically in the Catalinas since fires about a decade ago improved habitat for deer.
"It's not like the lions will be starving for large ungulates," Heffelfinger said. "They have a good prey base up there."
While environmental group leaders sometimes oppose the killing of one species of wildlife to protect another, the plan has won guarded acceptance from some in this case.
"The end goal for the two species, predator and prey, is coexisting as they have naturally done," said Mike Quigley, Arizona representative for The Wilderness Society. "While sheep numbers are artificially low, there may need to be some targeted predator control."
Others, including Sandy Bahr, director of the Grand Canyon Chapter of the Sierra Club, have more of a wait-and-see outlook.
"We're supportive of restoring bighorn sheep, but we're looking closely at the implementation of this mountain lion plan," Bahr said. "We will keep a close eye on them and make sure they don't just eliminate lions right and left. Lions are part of the system, too."
Randy Serraglio, Southwest conservation advocate with the Center for Biological Diversity, said he favored the Game and Fish plan - and he also sees a vital role for people.
"Part of what we're trying to do here is re-establish that balance between sheep and people," Serraglio said. "That means learning to coexist with sheep by observing trail restrictions and dog restrictions" in areas where sheep are released.
"With some education and a positive attitude about this reintroduction, it's an achievable goal," he said.
On StarNet: For more photos of bighorn sheep, go to azstarnet.com/gallery
did you know?
• Male mountain lions weigh 80 to 150 pounds, and females weigh in the 70- to 100-pound range.
• Their prey includes deer and javelina as well as bighorn sheep and other animals.
Source: Arizona Game and Fish Department
Contact reporter Doug Kreutz at firstname.lastname@example.org or at 573-4192. On Twitter: @DouglasKreutz