Mountain lion kittens P-48 and P-49 in their den in the Santa Susana Mountains/NPS

Editor's note: The following is an unedited release from Santa Monica Mountains National Recreation Area.

National Park Service researchers recently discovered two litters of mountain lion kittens in the eastern Santa Susana Mountains. A total of five kittens, three females and two males, were ear-tagged and returned to their respective dens earlier this month.

The Santa Susanas are a large mountain range that provides a critical habitat connection between the Santa Monica Mountains to the south and Los Padres National Forest to the north.

"Despite the challenges mountain lions in this area face, the animals we've studied appear to be reproducing successfully," said Jeff Sikich, a biologist with Santa Monica Mountains National Recreation Area. "The real challenge comes as these kittens grow older and disperse, especially the males, and have to deal with threats from other mountain lions and also road mortality and the possibility of poisoning from anticoagulant rodenticide."

The first litter of kittens, tagged June 8, are two females now known as P-48 and P-49. Their mother is P-35, an approximately six-year-old female that the National Park Service has been tracking since April 2014. Based on remote camera images, biologists suspect her previous kitten, P-44, did not survive into adulthood.

The second litter of kittens belong to P-39, an approximately five-year-old female researchers began tracking in April 2015. She gave birth to three kittens, a male known as P-50, a female known as P-51, and another male known as P-52. The den, discovered on June 22, was located in a cave-like area hidden beneath large boulders.

In both cases, the father is suspected to be P-38, based on GPS locations of him traveling and spending multiple days with P-35 and P-39 months before the kittens were born. Samples from the kittens were taken for genetic testing, in order to determine paternity with certainty.

Researchers located the kittens' den by analyzing the GPS locations transmitted from the mother's collar. For the first three weeks after the kittens' birth, the GPS points are typically localized in a cluster that is then used to determine the den's location. Even with GPS device in hand, the den can be difficult to find because of the thick brush and hidden crevices that mothers choose to hide their kittens in for protection.

These are the tenth and eleventh litters of kittens marked by National Park Service biologists at a den site. Two additional litters of kittens were discovered when the kittens were already at least six months old.

Since 2002, the National Park Service has been studying mountains lions in and around the Santa Monica Mountains to determine how they survive in an increasingly fragmented and urbanized environment. Funding for mountain lion research in the Santa Monica Mountains is provided in part through private donations to the Santa Monica Mountains Fund.