On Sept. 25, when the radio tracking collar of a young male mountain lion in the Santa Monica Mountains emitted a "mortality signal," indicating it had not moved for at least eight hours, biologists feared the worst.
The 2-year-old puma, one of only three known mountain lions left in the coastal range, was either seriously wounded or dead.
Wildlife ecologist Seth Riley went to investigate, pinpointing the puma's location from its collar and then heading out to the scrubby hills west of Topanga Canyon. There, he found the lifeless cat, its forelegs chewed and its head bearing several puncture wounds.
It appeared that P1 had struck again.
P1, short for Puma 1, is the dominant male mountain lion in the Santa Monica Mountains and the father of the dead cougar.
Riley and the other National Park Service scientists who track the region's mountain lions (also known as cougars or pumas) had been joyous in 2004 when P1 mated with the only other big cat researchers knew to live in the Santa Monicas. Later that year, she bore four kittens.
But since then, for reasons that remain unclear, P1 has gone on the attack, killing his mate and one of their offspring in 2005 and another cub in June. Now a third cub was dead, and P1 was the logical suspect.
When Riley returned to the ranger station to review the global positioning system data from P1's collar, he was surprised at what he found.
GPS data showed that at the time the latest cub was killed, P1 was at least 35 miles from Topanga Canyon, roaming an area far to the west near Point Mugu. And that opened the door to an interesting possibility: Perhaps there was another cougar in the range.
Genetic tests of swabs taken from the dead lion's claws confirmed that he had fought an adult mountain lion other than P1.
For Riley and his colleagues at the Santa Monica Mountains National Recreation Area, it was the latest twist in what has been an emotional saga.
For five years, they had tracked the mountain lions' movements, hoping their research would help them and the public better understand how this resilient species adapts and survives in urban parkland.
Now, the idea of another adult male, one that had never been tagged by scientists and whose whereabouts were unknown, had added another layer of mystery to the tale.
"We have always said, just because these are the lions we know about these aren't necessarily the only lions," Riley said. "Another lion could move in, or there's lions out there we just don't know about."
A solitary species
Riley and his colleagues at the largest urban national park in the U.S. began monitoring cougars in 2002, when they received state funding to launch the Mountain Lion Project. The scientific study was designed to allow researchers to learn more about the habits of cougars in the 154,000-acre park.
When they started the project, scientists had only a rough idea of how many pumas lived in the mountain range. Solitary by nature, the buff-colored cats generally avoid people. Bobcats, which look similar but are smaller, with tufts of hair sprouting from their ears, are much more prevalent.
To find the mountain lions at the beginning of the project, biologists looked for signs of the cats, then set up remote-controlled cameras in the hills and canyons of the Santa Monica Mountains and in the nearby Simi Hills.
Using the information they gathered, researchers were able to capture all four of the pumas caught on camera and fit them with collars containing radio transmitters.
The lions dubbed P1 and P2 roamed a huge territory in the Santa Monica Mountains south of the 101 Freeway.
The other two, P3 and P4, lived in the Simi Hills north of the 101.
When P2 gave birth in 2004, the biologists were understandably excited. The known cougar population had climbed to eight, although only six lived in the Santa Monicas.
But at the time, scientists quietly worried that the fragmented mountain range would not be large enough to support so many of the large cats, especially as freeways, business parks and houses steadily encroached on open space.
Male mountain lions, weighing up to 200 pounds, need about 150 square miles of "home range" to survive, and the smaller females about 40. Although male and female territories may overlap, males must stake out their own turf in which to roam and hunt prey, or eventually they will fall victim to the prevailing male.
In August 2005, scientists received the news they had been dreading: P1's radio collar showed him near a wooded area north of Mulholland Highway between Kanan and Las Virgenes roads. That put him in the exact area where P2 and her cubs were living.
Rangers believe P1 approached P2 as she was feasting on a freshly killed mule deer and that all or some of the pair's yearling cubs were nearby.
The two big cats brawled fiercely for several hours in the forested area. At the time, park biologist Jeff Sikich was close enough to hear the growls and howls.