The Santa Monica Mountains are experiencing a 'summer of kittens'

National Park Service biologists reported Wednesday that five mountain lion dens containing 13 kittens have been discovered in the Santa Monica Mountains and Simi Hills, marking the first time that many dens have been found within such a short time during an 18-year study of the species.

"This level of reproduction is a great thing to see, especially since half of our mountains burned almost two years ago during the Woolsey Fire," said Jeff Sikich, a wildlife biologist who has been studying the mountain lion population at Santa Monica Mountains National Recreation Area. "It will be interesting to see how these kittens use the landscape in the coming years and navigate the many challenges, both natural and human-caused, they will face as they grow older and disperse."

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The highest previous number of dens found in one year was four -- across 10 months in 2015, researchers said.

The five new litters included:

-- two males (P-82 and P-83) and one female (P-84) that were born to P-54 and discovered May 14. Researchers suspect the father is P-63 -- who was born in the Simi Hills and is only one of two male radio-collared mountain lions living in the Santa Monica Mountains;

-- three female kittens (P-85, P-86 and P-87) that were found June 19. The litter was the fifth for P-19 -- a 10-year-old mountain lion who is the oldest in the long-term study, but biologists haven't determined who the father is;

-- a female kitten and two males (P-88, P-89 and P-90) that were discovered July 6. It may be the first litter for the 3 1/2-year-old mother, P-65, who survived the Woolsey Fire and became the second radio-collared female mountain lion to cross the 101 Freeway in August 2019 and move northward into the Simi Hills. She crossed the freeway again last November and returned to the Santa Monica Mountains.

Researchers think P-63 -- who likely sired the kittens with P-54 -- is also likely the father because he and P-65 traveled together for three days in March;

-- a female kitten and a male kitten (P-91 and P-92) were found July 7 in a den in the Simi Hills in what was only the second time a litter of kittens has been discovered in the area. They were born to P-67 -- who was originally tagged as a kitten in the Simi Hills in 2018 --- and are suspected of being fathered by P-78, with whom she had traveled on multiple days;

-- two female kittens (P-93 and P-94) that were born in the central portion of the Santa Monica Mountains to P-80, who is estimated to be between 5 and 7 years old. The den was discovered Aug. 6, with the kittens estimated to be about 32 days old. Researchers also suspect that P-63 is the likely father since he and P-80 had traveled together for four days in early April.

Biologists visit the dens while the mother is away hunting for food, feeding or resting and perform a general health check, determine the sex of each kitten, take various body measurements, obtain biological samples and place a uniquely numbered and colored ear tag in each of the kittens, which are returned to the den before their mother comes back, according to researchers.

The National Park Service launched its study on mountain lions in and around the Santa Monica Mountains in 2002.