P-54, a three-year-old mountain lion living in the Santa Monica mountains, gave birth to a litter of kittens – males P-82 and P-83, and female P-84 – last May. Researchers believe this is her first litter. A mountain lion baby boom has occurred this summer in the Santa Monica mountains and Simi hills west of Los Angeles. Thirteen kittens were born to five mountain lion mothers between May and August, according to the Santa Monica Mountains National Recreation Area.