REGIONAL: Mountain lion study tracks big cats
Scientists examine how lions use big landscapes
By DEBORAH SULLIVAN BRENNAN | Posted: July 23, 2010 7:36 pm | No Comments Posted | Print
For a year and a half, he prowled the mountains of East San Diego County, slipping past fences and border patrols at least four times as he crossed back and forth into Mexico on a 100-mile trek.
He kept a low profile on the edges of civilization, living off the land and avoiding the confrontations with ranchers and motorists that can prove deadly to his kind.
The voyage of the 4-year-old mountain lion, designated M53 in a decade-long study on the movements, health and behaviors of the big cats, illustrates the species' vast range and stealthy existence.
Four other study lions died in recent months ---- one was struck by a car and three were shot ---- common hazards the felines face in their quest to hunt and breed.
The divergent travels of the lions, recorded through radio collars, demonstrate what these large predators need to survive, and how the landscape is closing in on them.
"We're hoping to use this information to help people learn how they can coexist with lions," said Walter Boyce, co-director of the Wildlife Health Center and a principal investigator on the study.
Multipurpose lions
The Southern California Cougar and Bobcat Study started in 2000 to find out how and when mountain lions preyed on bighorn sheep.
Peninsula bighorn had been listed as an endangered species just two years earlier, and part of their management plan called for limiting lion attacks on sheep.
Researchers with the UC Davis Wildlife Health Center began tracking lions with radio collars to figure out how to do that.
They found, to their surprise, that lions' taste in sheep varies considerably, and that sheep-eating mothers train their cubs to do likewise, but that the behavior occurs in occasional binges instead of a steady pattern, Boyce said.
Other questions quickly arose.
Officials at Cuyamaca Rancho State Park and Anza-Borrego Desert State Park wondered whether the lions traveled on hiking trails.
The National Science Foundation asked for research on the spread of feline diseases between domestic and feral cats, bobcats and mountain lions.
And conservation groups interested in maintaining linked wildlands wanted to know where lions cross between the areas.
The study found that lions circulate in and out of state parks, mostly eluding hikers, and that feline diseases can mutate to pass between species.
And it indicated what kind of crossing structures the animals might need to safely get past freeways (wider undercrossings, or some sort of walls that steer them toward a safe crossing), and which areas ---- such as the Interstate 15 corridor from Temecula into San Diego County ---- are most vital to connecting separate populations of lions.
Various groups contributed funding to the study, which has cost more than $1 million, Boyce said, and the lions became a kind of roving laboratory for wildlife inquiries.
So far, researchers have captured 53 mountain lions ---- some more than once ---- and 13 bobcats over 10 years, Vickers said.
"It's like we have these sort of multipurpose lions out there, and we're trying to get every type of information we can from them," said Winston Vickers, a veterinarian with the Wildlife Health Center at UC Davis and a principal investigator on the study.
Capturing the lions posed the first challenge.
Researchers found that trapping lions in cages was safer for the animals than using either snares or hounds.
Once an animal is caged, researchers shoot it with a tranquilizer dart from a blowpipe, sedating it for about an hour.
They weigh and measure the lion, take blood samples and fit it with a radio collar.
The flexible collar is fitted with a radio transmitter that emits a steady beep at a distinctive radio frequency.
The device also records location coordinates from a GPS satellite.
Every few months, researchers fly over the area, tracking individual animals by their signals and downloading their data for analysis.
The collars are used only for research, Vickers said, not to track and kill a lion that has preyed on pets or livestock.
The device also contains a switch that doubles the beep if a lion is inactive for eight to 12 hours, emitting what researchers call a "mortality signal," indicating that the animal may have died.
Mortality signals
Over the last few months, those signals have sounded with regularity.
In April, another wide-ranging male lion, M56, was shot at a ranch in Japatul, near Alpine, after killing domestic sheep.
The lion, captured and collared in May 2009, had wandered down the coast across Camp Pendleton and passed through Oceanside.
Although researchers thought that I-15, with its high-speed traffic, represented a nearly uncrossable barrier to lions, M56 passed under the freeway into Valley Center at the Old Castle/Gopher Canyon exit, slinking through a concrete underpass that provided little of the cover that lions prefer.
"It was about the middle of the night, so there probably wasn't much traffic," said Randy Botta, an associate wildlife biologist with the Department of Fish and Game. "There's really no vegetation or much of a shoulder."
The lion continued through Valley Center into Escondido, passing within a couple of hundred yards of Botta's Valley Center home before apparently slipping through a wildlife undercrossing on Valley Center Road.
The lion's movement across the highways encouraged researchers, who feared that lions in the Santa Ana Mountains, which extend from Orange County into northern San Diego County to the west of I-15, were so geographically isolated that they were at risk of inbreeding and genetic defects.
Mountain lions, which once roamed over interconnected mountains in Southern California, are clustered in pockets of wildland that seem more like archipelagos, separated by developments and freeways.
M56, unexpectedly, had traversed the region safe from cars, which have killed a quarter of the animals in the study, Vickers said.
Another 25 percent are killed by trackers or property owners after the cats have killed pets or livestock.
As M56 passed a sheep farm in Japatul, the hungry lion killed more than a half-dozen domestic sheep.
Animal trackers for the U.S. Department of Agriculture's Wildlife Services shot the lion after the farmers obtained a state depredation permit, or legal permission to kill an animal preying on domestic animals.
The lion had escaped one leading cause of death for Southern California lions, only to succumb to the other.
Three other lions in the study died in short order.
A male, M57, was hit by a car on the 241 toll road in Irvine in June.
A female, F51, was shot July 3 in an unincorporated area of Orange County, and F45, a female with cubs, was shot midmonth in the De Luz area near Fallbrook.
Wildlife authorities are investigating the two shootings, but have not located the cubs.
Their deaths confirm what scientists suspected: While lions in the wilderness die from disease, or fights with other lions, those crossing urban areas face a different threat.
"The risk of death is higher when they happen to be moving in areas that put them in contact with people," Vickers said.
Really big landscapes
Although several lions died recently when they crossed paths with humans, others in the study have circulated throughout wild patches of Southern California undetected by residents.
One traveled 60 miles from Cuyamaca Rancho State Park to the San Pasqual Valley around the San Diego Zoo's Wild Animal Park, Vickers said.
Another roamed 100 miles, from Anza Borrego Desert State Park to the San Jacinto Mountains near Palm Springs.
Given the chance, scientists said, mountain lions can slip past humans without incident.
Scientists said they want to give the animals the chance, and the space. About one-sixth of long-standing mountain lion habitat is projected to be lost to development by 2030, based on research by Colorado State University researchers, Vickers said.
Conservationists hope to set aside some of that land to connect wild places such as state parks and national forests, said Zach Principe, a biologist with the Nature Conservancy.
"The thing is to keep them away from people, because things happen," he said. "They're not tame animals, and they get wild."
As top predators, mountain lions provide signals about the condition of "really big landscapes," Vickers said.
While the recent mountain lion deaths appear to paint a bleak picture of their prospects, the study's findings offer hope about their resilience, scientists said.
"They are potent symbols in people's minds of wildness, and wild landscapes," Vickers said. "So at least one thing that defines the study is that this landscape does retain a lot of important connections. There is a lot of mountain lion habitat still out there."
Call staff writer Deborah Sullivan Brennan at 760-740-5420
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