Two blue-eyed mountain lion kittens born to a young mother and a father that gets around were found earlier this month in the Santa Monica Mountains, marking the 13th litter discovered by researchers in the area, officials announced Tuesday.

The female and male siblings have been dubbed P-59 and P-60, and were discovered by National Park Service and California Department of Fish and Wildlife biologists. The kittens will now be part of a long-term study by the National Park Service on carnivores in and around the Santa Monica Mountains.

But while their birth marks a victory of sorts in maintaining a declining population of pumas, researchers say they are troubled by their lineage.

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At 2 years old, their mother, P-53, is the youngest puma to bear offspring. This is her first litter. Their father is suspected to be P-12.

Researchers say DNA results are pending, but P-12 is suspected because an area resident heard mountain lions “interact near their property in April.” GPS and photo evidence placed both P-53 and P-12 in that area at that time.

P-12 is the only lion documented that has successfully crossed into the Santa Monica Mountains from the north. Biologists are concerned because he has mated with his own offspring and their offspring, which reduces the genetic diversity of the mountain lions in the area, researchers warned.

“If P-12 is in fact these kittens’ father, that also means he’s their grandfather, their great-grandfather, and their great-great grandfather,” said Jeff Sikich, a biologist with Santa Monica Mountains National Recreation Area, a unit of the National Park Service. “Inbreeding to this degree really highlights the need for providing safe passage across the 101 Freeway so new mountain lions can enter the population and breed.”

Researchers have noted both triumphs and tragedies in the last 10 months in Southern California’s mountain lion community.

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A 7-month-old kitten, known as P-52, was struck and killed by a vehicle on the freeway on Dec. 20 just a few miles from where its mother, P-39, died earlier that month. Another of her kittens, P-51, was killed on the same freeway in January.

In April, another mountain lion kitten was discovered.

Earlier this month, a male mountain lion named P-55 was documented successfully crossing the 101 Freeway — a rare event for the region’s big cats. He represented only the fourth case of a successful crossing since the NPS began its mountain lion study in 2002.

“There is always some good news and some bad news, and that’s a similar pattern we’ve seen in this study,” said National Park Service spokesman Zach Behrens. “This is a long-term study. We’re going to see life and death through out it. The goal over time is to preserve these species for future generations.”

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Researchers believe the Santa Monica Mountains can hold 10 to 15 cougars at a time. Biologists have tracked more than 340 bobcats, 145 coyotes, and 60 mountain lions over the course of the study.

Wildlife advocates and activists have called for a wildlife corridor over the 101 Freeway and Liberty Canyon in Agoura Hills has been identified as the ideal spot. A proposal is currently being drawn by CalTrans and fundraising efforts via SaveLACougars.org is underway with the National Wildlife Federation and Santa Monica Mountains Fund.

Editor’s note: An earlier version of this story incorrectly stated that 10 to 15 mountain lions are studied at a time. That is the number of mountain lions believed to be in the Santa Monica Mountain range at one time.