When they left the dead deer in the pickup bed on the night of March 5, UC Davis researchers Ken Logan and Linda Sweanor weren’t too concerned about leaving the carcass unsecured in cougar country. The 90-pound doe, after all, was four feet off the ground, surrounded by the 16-inch-high truck bed and stiff with death and cold. So they merely joked that one of them should put on night-vision goggles and stand guard. Then they went to bed.
Partners in research and marriage, Logan and Sweanor had spent their careers studying cougars. They were the principal investigators on the most extensive cougar study ever done, in New Mexico’s San Andres Mountains in 1985-95. Sweanor’s thesis for her 1990 master’s degree at the University of Idaho was on cougar social organization; Logan’s 2000 doctoral dissertation there was on cougar ecology.
So, last January, when they settled into rugged Cuyamaca Rancho State Park above San Diego to lead a new UC Davis research project, they had studied cougars more intensively than had anyone else in the world.
Even so, the Cuyamaca cougars would show them something new.
A different kind of cougar
Biologists began thinking of Cuyamaca’s cougars as a breed apart in the late 1980s, when a growing number of visitors reported encounters with cats that were unusually bold. "Typically, lions stay away from people," said Cuyamaca Park Superintendent Jim Burke. But at this park, from 1993 to 2000, visitors reported seeing mountain lions 201 times. Sixteen times, lion behavior was deemed threatening to human safety; nine times, officials killed the lions.
Then, on Dec. 10, 1994, the worst occurred – a cougar killed school counselor Iris Kenna as she hiked alone near Cuyamaca Peak. It was the first time a cougar had killed a person in California in 80 years.
Meanwhile, just a few miles to the east, researchers from the UC Davis School of Veterinary Medicine were conducting what seemed to be an unrelated study. There, in the Peninsular Ranges in Anza-Borrego Desert State Park, an endangered population of fewer than 400 bighorn sheep was shrinking fast. Beginning in 1992, wildlife veterinarian and ecologist Walter Boyce, director of the UC Davis Wildlife Health Center, led the effort to find out why. Using novel investigative techniques, including DNA fingerprinting, Boyce and his graduate students discovered that disease was one key factor, but more important was predation: Of the 61 radio-collared sheep that died during the study, cougars killed 42.
For Boyce, when the cougar killed Iris Kenna in Cuyamaca, the two situations merged into one. "That really heightened my awareness that this wasn’t a single-species issue or a single-location issue," Boyce said. "The public-safety component of cougar biology was the opposite side of the coin to the endangered-species component – bighorn sheep."
Now Boyce began to envision a new study that would look at the situation long-term on a regional scale. The Southern California Ecosystem Health Project would concurrently examine the relationships of lions, humans, sheep – and deer, which seemed to be the factor that drew lions into close proximity with both sheep and people.
Logistically, the researchers would need to put radio collars on as many deer, sheep and lions as they could catch. UC Davis would employ, besides Boyce, four biologists to work full time on the collaring, tracking and data-analysis elements of the project.
Boyce began the painstaking work of building political and financial support. His key allies were experts like Mark Jorgensen, a resource ecologist for California State Parks, who grew up in the Anza-Borrego Desert and returned from college to work for its preservation; husband and wife team Steve and Alison Torres, the biologists for the California Department of Fish and Game responsible for the management of sheep, mountain lions and deer in the entire state; and Esther Rubin, a Boyce Ph.D. graduate who had become a conservation fellow studying bighorn sheep for the Zoological Society of San Diego.
Cougar enjoys protection
The political elements were complex. For a creature that most Californians will never see, the mountain lion is remarkably charismatic. In 1990, California voters approved Proposition 117, banning cougar hunting. In 1996, even after cougar numbers had begun to rise, and cougars had killed Kenna in Cuyamaca and Barbara Schoener near Sacramento, voters again endorsed cougar protection. Yet hunting interests continued to lobby for lion management, while sheep advocates were nervously watching the lions eating away at the Peninsular Ranges bighorn population.
In that political climate, Boyce feared the plan to study the lions might be seen as a threat to their protected status. As he worked to build support for the new study, Boyce stressed the importance of objective research: UC Davis intended, he said, "to get good science done, and make it available to wildlife managers and the public so it could be implemented into wise policy decisions to ensure public safety and the best stewardship of natural resources."
By mid-2000, Boyce had amassed $1 million in cash and in-kind commitments – enough to carry the project for three of the 10 years he felt necessary.
He hired Linda Sweanor and Ken Logan as his mountain lion specialists and field biologists Jim Bauer and Casey Lydon as scientific aides jointly employed by UC Davis and Fish and Game.
Closing in on their first lion
In January, Sweanor and Logan moved into a cabin in Cuyamaca Rancho State Park. One morning in late February, Sweanor stepped outside and found footprints in the snow that said a big cougar had walked under her floorboards in the night. The team decided to try to catch and radio-collar this cat. They asked the park rangers to get them a roadkill deer for bait.
Mountain lions are supremely adapted for killing large prey. Weighing 70 to 160 pounds and stretching 5 to 7 feet long from nose to tail tip, they are equal in size to most deer. Their short muzzles, long legs and powerful shoulders are heavily muscled for bringing down struggling animals.
A ranger called late on March 5 with the location of a roadkill doe. Logan retrieved it, then left it for the night in the bed of the project’s Toyota Tacoma pickup truck, tailgate up. He and Sweanor joked about guarding the carcass, then slept.
"The next morning, Ken went out to the truck at about 7," Sweanor recalled. "He came back in and said, ‘Well, the carcass is gone.’ And we went out and there was no deer – just two deer hairs stuck on the side of the truck."
A cougar apparently had hauled the deer out of the truck bed and out of sight. It had carried the carcass so high off the ground that Logan and Sweanor had trouble picking up a drag trail on their hands and knees. When they finally did pick one up, it led them the length of two football fields to a cache in dense chaparral. There the biologists set their snares. Two nights later, they made the first lion capture of the new project: a healthy, 4-year-old, 140-pound male. He was tranquilized, fitted with a radio collar, designated Male 1 and released.
On March 28, the team collared a second male. M2 was 2 to 3 years old and weighed 109 pounds. On July 14, cougar M3 was caught. M3 was only about 8 to 10 months old and still living with his mother; he weighed 58 pounds. He was fitted with a radio collar that would expand to accommodate his growth.
A broad hunting area
By the time the summer visitor season ended in Cuyamaca Rancho State Park, the team was starting to build a picture of the lions’ movements. In typical cougar fashion, they covered a lot of ground. M1 tended to ramble throughout the park and to the west, covering a range of at least 140 square miles – three times the size of the park. M2’s range covered about 76 square miles, including large areas south and east of the park. M3 and his mother were moving in and out of the park, staying put for a few days each time they killed a deer.
Sometimes, as Sweanor takes her telemetry gear up on Cuyamaca ridges to scan for the lions’ radio signals, she thinks back to that night when M1 stole away the deer carcass. "I know that mountain lions are strong. A single lion can pull down a bull elk six times its weight," she mused. "Still, that cat pulling the deer out of the truck – I would have liked to have seen it myself."