When Ilene Dondlinger jumped on the mountain lion attacking her miniature schnauzer in the early hours of 5 December, she reacted without thinking. The 54-year-old wrestled with the big cat in her backyard, desperately trying to open its jaws to save her beloved dog Pumba. But there was nothing she could do.

“I couldn’t prise its jaws open, no matter what I did,” Dondlinger said, detailing how she punched, kicked and jumped on the big cat, even putting her knee to its throat in desperation.

“I don’t have any children so he was my baby. But I couldn’t get him out … I knew when my little dog was gone.”

Dondlinger was left with bruises after the struggle. She said the mountain lion had barely reacted to her retaliation, only growling at her once Pumba was dead.

Mountain lions, known as pumas, panthers, cougars or brown tigers depending where you are in the western hemisphere, live across California. A typical adult male weighs 110lb to 180lb and a female 80lb to 130lb, according to the Mountain Lion Foundation. They are rarely dangerous to humans but attacks on pets and livestock do happen.

Ilene Dondlinger with her dog Pumba. Photograph: Courtesy Ilene Dondlinger/Facebook

An animal known to researchers as Puma-35 is believed to have carried out the attack. It inhabits the Simi Hills where Dondlinger lives, about 40 miles from Los Angeles. When the big cat became aggressive in the tussle, Dondlinger had to retreat indoors for her own safety. Police officers responding to the call were met with a grisly sight of P-35 eating the dog when they peered through a window into the backyard.

But despite Dondlinger’s grief for a dog that had spent more than a decade by her side, she does not want P-35 killed.

“It won’t bring Pumba back,” she said. “Us humans continue to push them out of their space, continuing to build houses in their territory. They have a right to be here, too. I don’t ever want anybody to go through what I’ve been through because it was the most horrific five minutes of my life … But if humans keep killing everything off, eventually there won’t be any wildlife left.”

A study in March found that urbanisation is threatening mountain lions with local extinction in southern California within 50 years, largely from inbreeding caused by the state’s road network, which traps subpopulations of the big cat on genetic islands. Cars, rodenticides and depredation orders also threaten them. Conservationists are planning to build the largest wildlife crossing in the world to help the predator’s survival in and around California.

It was not the first time the big cat, nicknamed Santa Susana Mountains Mom by researchers after giving birth to many litters of kittens, is believed have preyed on a pet in the neighbourhood that evening.

Around 10pm, police were called to a nearby property in Evening Sky Drive after another resident complained a mountain lion had attacked his dog while he was walking near his home. Around 1am, the same resident called again as the mountain lion was on his front porch, staring in through a window at his dog.

A neighbor reported a mountain lion on his front porch. Photograph: Simi Valley police department

Later that evening, Dondlinger let Pumba out to relieve himself just after 2am and he chased the mountain lion in her backyard, only for the mountain lion to grab the dog. The big cat left Pumba’s body when police arrived and he has since been cremated.

Minnesota-born Dondlinger said she thought the big cat was sick and that might have been why it came down from the hills.

“If it had been a healthy cat, you probably wouldn’t have been talking to me right now. It was skin and bones. Its hair was really, really gross and it had the most putrid smell,” she explained. Dondlinger said the big cat barely responded to her desperate efforts to save her dog. Researchers said they would need to capture the mountain lion to check its health and verify its identity.

On Thursday morning, a male mountain lion was caught and tranquilized in a backyard in Simi Hills. But P-35 has not been captured by authorities.

Some of the media reaction to the incident has been frenzied, warning of more attacks as a dangerous cougar stalks the neighbourhood. The concern has divided some residents in the area but authorities have clear rules about such incidents.

Cmdr Steve Shorts from the Simi Valley police department told the Guardian: “If there’s not a public safety risk where that animal is going to injure or seriously harm a person, we are not allowed to use deadly force on that animal. It has to be justified. If it’s eating a domestic animal, the dog that is unfortunately attacked, that’s considered property, that’s not a person.”

The Mountain Lion Foundation advise people living alongside wild animals to keep pets inside at night if coyotes and mountain lions live in the area, put up fences, install frighten devices and discourage deer from entering property.

The California department of fish and wildlife has advised people to avoid hiking at dawn and dusk, keep dogs on leashes in mountain lion territory, never run and fight back if attacked. But attacks on humans are very rare, fewer than 20 in the last 100 years, and most mountain lions avoid human settlements.

Asked about P-35’s future, Shorts said: “Hopefully what’s going to happen is that this is just a small area in that mountain lion’s range and it’s just decided to hang out in this area right now and it’s going to go into another area that’s more secluded. Hopefully then it will stop.”