Last week, two fierce growls shattered the quiet in Inverness’s Second Valley as Sabrina Pelayo was on her deck painting with her son Shaun. What they initially thought might be a couple of raccoons in an argument turned out to be something more dramatic: two mountain lions, locked in an apparent struggle, perched high in the trees. Suddenly, one of the lions fell from the tree, with the other swiftly descending in pursuit. They disappeared from sight. Cougars, though native to West Marin, are rarely seen in populated residential areas like Second Valley. The Aug. 12 incident was the first time that Dave Press, a wildlife ecologist with the Point Reyes National Seashore, had heard of two mountain lions spotted together in a residential neighborhood in the area. The sighting was so unusual that locals offered a range of alternative explanations. A neighbor down the road from the Pelayos assumed it was “just a couple of cats having a bad day.” While no one can say for certain what the big cats were doing, Mr. Pelayo speculated that “it was just something over turf,” a theory supported by Mr. Press. “If a new mountain lion wanders into an established territory, the resident lion won’t be too happy about it,” Mr. Press explained. He also suggested the possibility that they were copulating, noting that “the mating behaviors of certain wildlife species can seem very intense and aggressive.” Wildlife experts have no reason to believe the local mountain lion population is increasing. State wildlife officials estimate there are between 4,000 to 6,000 mountain lions in California, though it’s unclear how many roam in West Marin. The seashore doesn’t have a formal monitoring program, but Mr. Press estimated there may be four to six cougars in the area. The Pelayos did not fear for their safety. According to the California Department of Fish and Wildlife, there have been only 24 verified mountain lion attacks on humans in the state since 1986, and none in Marin in recent history.