Science
L.A.'s mountain lions become more nocturnal to avoid people. Does it come at a cost?
Griffith Park’s late celebrity mountain lion P-22 took the night shift to avoid hordes of hikers, bikers and dawdlers who frequented his home in the heart of Los Angeles — and it’s a pattern replicated by other pumas in the region, according to a new study.
The move to a later schedule is an encouraging example of a species doing its part to coexist in a bustling megalopolis, according to researchers from UC Davis and other institutions who conducted the study.
But the temporal gymnastics they perform may come at a cost, experts said, consuming energy and limiting the amount of time they can spend on critical tasks such as hunting. And it may compound other urban stressors, like whizzing traffic and rat poison.
The study, published last month in the journal Biological Conservation, found that Southland mountain lions became more nocturnal and less crepuscular — i.e., active at dusk or dawn — in popular recreation areas.
To examine the impact of recreation on the lions, researchers used GPS and activity data gleaned from the tracking collars of 22 mountain lions roaming the Santa Monica Mountains and surrounding region between 2011 and 2018.
They also drew data from Strava, a popular app in which users publicly document runs, hikes and more to determine how much recreation was happening in each lion’s home range, and to test how it influenced the patterns and timing of their activity.
The “most nocturnal” puma in the study was the late P-41, who inhabited the Verdugo Mountains, a range bounded by freeways and development on the northeast edge of the San Fernando Valley, and a recreation haven. Ranked second was P-22, affectionately called the Brad Pitt of mountain lions when he stalked the Hollywood Hills.
The study revealed that female lions were less nocturnal than males, possibly because males pose a threat to them and their kittens.
(National Park Service via Associated Press)
Researchers wondered if mountain lions who were exposed to more recreation would become immune to it — and simply not care.
“We saw the opposite,” said Ellie Bolas, lead author and a PhD candidate at UC Davis.
“Seeing that mountain lions are flexible in their activity and sensitive to recreation is, I think, a reason we can feel optimistic that they’re willing to avoid us and want to avoid us,” she added.
Other institutions involved included Cal Poly Pomona, the National Park Service, UCLA, the University of Nebraska and Harvard Westlake High School.
The findings are good news for Angelenos worried about becoming a lion’s lunch — given that the cats are steering clear of people. And it helps explain how the apex predators manage to hack it in an intensely urban environment. Los Angeles is just one of two megacities in the world that are home to a big cat; the other is Mumbai, in India, where leopards prowl the streets.
So why are local lions rearranging their schedules for people? The new study notes that animals might high-tail it to areas where there are less people when they can. But in the greater L.A. metropolitan area, with more than 18 million people, even natural areas get gridlocked. So they adopted another strategy.
The National Park Service has monitored lions in and around the Santa Monica Mountains for more than 20 years, which is where the long-term data for the recent research came from.
“A major thing that we’ve been studying all along is the effects of urbanization and fragmentation on these animals,” said Seth Riley, study co-author and branch chief for wildlife at Santa Monica Mountains National Recreation Area, a unit of the park service.
The new study revealed that the lions’ timing shifts weren’t more pronounced on weekends when recreation spikes, contrary to what researchers expected.
There were also differences between the sexes, with female mountain lions found to be more active during the day and closer to sunrise. Researchers surmised that they avoid overlapping with male lions who will kill kittens in tow — and sometimes even the females themselves.
The least nocturnal puma tracked was P-13, a female with a home range in the central and western Santa Monicas.
Beth Pratt, California regional executive director for the National Wildlife Federation, said that while it’s good news that the charismatic cats are “coping,” there are likely tradeoffs.
“By switching their hunting strategy, it’s not ideal,” said Pratt, who was one of P-22’s biggest boosters. “It takes more energy, it doesn’t give them as many options, but the animals here are doing their part.”
People should pitch in, too, by minimizing challenges, she said. Panthers stalking the Santa Monica Mountains are imperiled by inbreeding because of freeways that essentially lock them in — and visitors with needed genetic diversity out.
“At a certain point they’re not going to be able to cope with all these challenges stacked up,” she said, pointing to threats such as cars and rodenticides — both of which took a toll on P-22. He was captured and euthanized in late 2022, deemed too sick to return to the wild because of injuries and infection.
One way to give lions “the edge” is by putting up wildlife crossings, said Pratt, who is a major force behind the largest such passageway in the world rising over the 101 Freeway in Agoura Hills.
The more than $90-million Wallis Annenberg Wildlife Crossing currently under construction is seen as a potential lifeline for the lions of the Santa Monicas. Without an outlet, the population is at risk of blinking out.
Pratt said the new study shows that actions as seemingly innocuous as how we site trails and enjoy the outdoors can impact the species — and that it would behoove us to consider our approach as we navigate a biodiversity crisis.
“It’s not that we shouldn’t do them, but how can we do them differently so that animals aren’t as impacted,” she said.
Bolas said there’s currently no research to tell us if the lions’ flexibility in the timing of their activity is also a cost to them, but that “it very well may be.”
Revelations from the study arrive as some Southern California and Central Coast cougars are at a crossroads.
California wildlife officials are poised to decide whether to designate six isolated clans of pumas as endangered or threatened species under state law.
The state Fish and Game Commission in 2020 granted the cougars who are roaming regions between Santa Cruz and the U.S.-Mexico border temporary endangered status as a candidate to be listed under the state Endangered Species Act.
A final decision is expected next year.
Science
Video: NASA Announces Artemis III Crew
new video loaded: NASA Announces Artemis III Crew
transcript
transcript
NASA Announces Artemis III Crew
NASA announced the crew of Artemis III mission, which will fly to low-Earth orbit to test rendezvous and docking maneuvers with one or two lunar landers.
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“I am excited to welcome you as the next crew in the Artemis journey to successfully return to the moon — this time to stay.” “I’m honored by the role that I’ve been given. I’m also very humbled by the task in front of us. But first and foremost, I’m grateful.” “So with that, the Artemis II crew, comrade, hands you the baton. You got the controls.” “As you know, we had a significant anomaly at our Launch Complex 36A on May 28. We’ve redoubled our efforts and are moving forward.”
By Alisa Shodiyev Kaff
June 9, 2026
Science
Santa Monica Mountains’ last steelhead trout survived the Palisades fire — and even had babies
Scientists feared the Santa Monica Mountains’ last remaining steelhead trout were dead, smothered by debris flows unleashed by the Palisades fire.
But the endangered fish surprised them: A team of biologists recently spotted 30 of the rare trout — and 21 babies — in Topanga Creek.
“There was a lot of happy dancing in the creek,” said Rosi Dagit, principal conservation biologist for the Resource Conservation District of the Santa Monica Mountains, which works with public and private landowners to conserve natural resources.
That’s because the steelhead here are endangered, at both the state and federal levels. Once, they swam in most streams of the Santa Monicas, but their numbers plummeted amid overfishing and coastal development. Increasingly frequent wildfire has further stressed their habitat. Topanga Creek, a biodiversity hot spot, is home to their last known population in the mountains that stretch from the Hollywood Hills to Point Mugu in Ventura County.
The trout that were spotted, including this one, are part of a distinct Southern California population that’s listed as endangered at the state and federal levels.
(RCDSMM Stream Team)
The California Department of Fish and Wildlife spearheaded a complex mission to rescue trout threatened by the Palisades fire that sparked in January 2025.
Time was of the essence. The fire hadn’t yet been fully contained. But rain was on the way, which would sweep massive amounts of sediment from the denuded hillsides into the water. Fish are often killed this way.
Crews stunned the fish with electricity, scooped them up in buckets, trucked them to a hatchery and ultimately moved them to Arroyo Hondo Creek in Santa Barbara County.
Within days, Topanga Creek was choked with mud. Some assumed the fish left behind were goners.
But in March, the conservation district’s team found four. The following month, when water conditions were clearer, they saw more.
“These fish continue to amaze me,” said Kyle Evans, environmental program manager for the state Department of Fish and Wildlife, who had seen the damage to the creek. “I had seen populations get wiped out in similar situations. So when I heard, I was thrilled.”
Evans surmises the fish that survived were in an area of the creek where less charred material and sediment were swept in.
“These fish likely hunkered down, were hiding under some rocks or places to try to get away from the main concentration of flow,” he said. “And luckily they weren’t buried.”
The ones that were spotted were fairly small, around 6 to 14 inches. Rainbow trout and steelhead trout are the same species, but with different lifestyles. If the fish remain in freshwater, they’ll be considered rainbows. However, they can migrate to the ocean and become steelhead, where they typically grow larger before returning to their natal waters to spawn.
Topanga Creek hasn’t fully recovered from the damage it sustained, but scientists say it’s looking better. Surveys last year were “so depressing,” Dagit said, with very few animals, and stretches that were essentially transformed into flat roads from all the sediment buildup. Some of the riparian canopy burned right down to the creek.
Then came 32 inches of rain over the last nine months, scouring out and moving sediment, creating deeper pools. Dagit said they recently found newt egg masses for the first time in years, as well as a few adult newts and many frogs. Plants that provide cover are starting to recover.
She provided photos comparing certain pools last year and this year, some dramatically transformed. In September 2025, the Shrine Pool could have been an overgrown hiking trail. This April, it was filled with shallow water.
The Shrine Pool in September 2025, left, and the same location in April 2026, right, with RCDSMM’s Isaac Yelchin donning a wetsuit.
(RCDSMM Stream Team)
Topanga Creek is home to another endangered fish, the small but hardy northern tidewater goby, often described as cute. Not long before the trout operation, Dagit led a rescue of hundreds of these fish too. Many were repatriated to the lagoon at the mouth of the creek in a moving ceremony last June.
There’s still the matter of what to do with the trout that were moved to Santa Barbara County last year. Evans would like to bring them home to the Santa Monicas at some point, but isn’t sure if it will happen. On one hand, they could bolster the small, genetically isolated surviving population. On the other, they might inadvertently bring in a disease or bacteria. There is some time to decide. Evans estimates the creek still needs to recover for two to three more years.
For now, the fish are functioning fine in their adopted creek. Experts worried the trauma wrought by the move would disrupt their spawning process, but they had babies that spring. This year, they spawned again.
Science
Pacifica pier cracks, another coastal casualty as seas continue to rise
The Pacifica Municipal Pier was shut down and taped off Thursday after city workers noticed cracks running through the landmark structure and concrete chunks falling into the ocean.
It’s just one of many coastal California structures that have recently crumbled under pressure from a rising and relentless ocean.
Officials from the small, beach city south of San Francisco said the pier was closed due to “cracking, separation, and displacement of the concrete walkway and structural elements.”
It will stay closed while structural engineers asses its safety.
Photos taken by city employees show a wide crack that runs from top to bottom and across the structure as well. Other photos show a large horizontal crack under the foundation of a small restaurant on the pier, the Chit Chat Cafe.
The cafe was also shut down.
This is not the first time the 53-year-old pier has shown signs of stress. In 2021, part of it was shut down after handrails along the edge collapsed. And in 2023, after a series of storms pummeled the Central California coast, damaging parts of the pier, the structure was partially closed for more than year.
Those same storms caused extensive damage in Aptos and Capitola, 70 miles south, where piers and waterfront infrastructure were swept away or damaged.
In 2024, a 150- to 180- foot section of the Santa Cruz wharf was ripped off by powerful waves.
At least 10 of the state’s dozens of coastal public piers were closed for part or all of 2024 due to structural damage sustained in winter storms since 2022. At least five others have longer-term upgrades planned to address structural issues.
“These things are costly to maintain,” said Zach Plopper, senior environmental director at Surfrider. “They are a part of our California coastal culture in many ways, but we’re going to need to reckon with, one, the state that they’re in, and two, the continuous and worsening threats they’re going to experience,”
He said most of the piers were constructed in the early 1900s, and they weren’t built to withstand decades of rough seas, storms and rising sea level.
“With this incoming El Niño, which is forecasted to be significant, and this marine heat wave we’re in the midst of, we’re kind of in uncharted waters as far as what this winter could bring in terms of storms and swells to the California coast, and we’re likely going to see a lot more damage,” he said. “Not just piers, but roads and other coastal infrastructure up and down the state.”
There was no storm in Pacifica earlier this week, so no single event could be blamed for the destruction.
However, a 2025 report from an outside engineering firm, GHD, found that several sections of the pier were in “poor” or “serious” condition, and they recommended closure before anticipated storms or events that could “subject the piles to high winds, swells and large waves.”
The firm found several areas of the pier where concrete was missing and rebar was exposed and corroding.
“The pier has continued to experience high winds and large waves in a harsh marine environment,” the engineers wrote in the report, noting that continuous exposure to seawater or marine spray was “detrimental” to the structure.
A 2023 city report estimated it would cost $19 million to repair.
That same year, a state law was enacted to require local governments along the California coast to plan for sea level rise in the coming decades.
Sea level has risen some 8 inches, on average, along the coast in the past 150 years, Plopper said, and researchers anticipate another foot in the next 25 years.
“We’re going to see profound shifts on our coastline, none that we have ever experienced before, and building static structures on the coast just doesn’t work all that well,” he said. “We’re going to have to make some really hard decisions.”
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