Biologists with the National Park Service believe that the two male kittens and one female kitten are the first litter for the three-year-old mother, P-54, and that the presumed father, P-63, may be a first-time father who may have brought genetic diversity into the species' population in the Santa Monica Mountains.
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P-63 is a male mountain lion born around December 2016 who is known to roam between the Simi Hills and the Santa Monica Mountains. He is the only living tracked lion in the area that biologists say has found a way to cross back and forth over or under the 101 Freeway.
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"The last litter of kittens that we marked at a den was from P-19 during the summer of 2018,'' said Jeff Sikich, a biologist who has been studying mountain lions for the Santa Monica Mountains National Recreation Area since 2002.
"That litter was likely the product of inbreeding, which is just one of the serious problems facing the isolated mountain lion population in the mountains south of the 101 Freeway. We're hoping this circumstance is totally different, but only genetic testing will tell us for sure.''
Park Service biologists determined that all three mountain lion kittens appeared healthy, each was given an ear tag to help identify them in the future and returned to the den after samples were taken for genetic testing. The kittens were estimated to be 19 days old at the time.
The kittens' likely father -- the only adult radio-collared male mountain lion living in the Santa Monica Mountains -- was initially captured in February 2018 with his mother P-62, north of the 101 Freeway in the Simi Hills and outfitted with a GPS collar, according to the National Park Service. Since then, he has crossed the freeway three times and stayed in the Santa Monica Mountains since December 2018, biologists said.
The kittens' mother was born in January 2017 and marked with a tracking device the next month while her mother, P-23, was away from the den, according to the National Park Service. P-23 was subsequently found dead near the side of Malibu Canyon Road in January 2018, after being struck by a vehicle.
P-63 was repeatedly located with the kittens' mother over two days, which is generally an indication of mating interaction, according to biologists.
About 90 days later, researchers noticed a series of localized GPS locations indicating that the kittens' mother had either given birth or was feeding at a kill site.
The kittens' births mark the 17th litter to be marked at a den site over the course of the long-term study to determine how mountain lions in and around the Santa Monica Mountains survive in an increasingly fragmented and urbanized environment.
Planning and fundraising is underway for a wildlife crossing over the 101 Freeway in the Liberty Canyon area of Agoura Hills that would provide a connection between the small population of mountain lions in the Santa Monica Mountains and the larger and more genetically diverse populations to the north.
In a unanimous decision in April, the California Fish and Game Commission moved a step closer to protecting six struggling mountain lion populations, including those in the Santa Monica and Santa Ana mountains, under the state's Endangered Species Act.
The commission's decision cleared the way for a yearlong review on whether the six populations of mountain lions should be formally protected under the state act, with the act's full protections applying during the yearlong candidacy period.
Supporters are seeking "threatened species protection,'' which is designed to protect species at risk of extinction in the foreseeable future without improved management, involving the "most imperiled populations'' of mountain lions in California, according to Tiffany Yap, a biologist at the Center for Biological Diversity and primary author of the petition.
Researchers with the National Park Service, UC Davis and UCLA warn that if enough inbreeding occurs, the Santa Ana population could go extinct within 12 years, and the Santa Monica population within 15.
The state Department of Fish and Wildlife had recommended the move shortly after P-56, a male mountain lion in the critically endangered Santa Monica population, was killed in January under a state-issued depredation permit by a landowner who had lost livestock to the big cat.