A litter of four mountain lion kittens were discovered in the Simi Hills area earlier this month, the National Park Service stated Tuesday.

Researchers found the kittens nestled in a rocky den while their mother was away on June 11.

Video posted by the Park Service showed two of the kittens hissing and clawing at the camera as they remained tucked away in their den.

The Simi Hills were described by officials as a small area of habitat wedged between the Santa Monica and Santa Susana mountain ranges.

The four female kittens are now known as P-66, P-67, P-68, and P-69.

Researchers have been tracking the kittens’ mother, P-62, since January, according to the news release. Wildlife officials figured she had given birth because she had been making return trips to one certain area.

The den is the first documented in the Simi Hills, between the 101 and 118 freeways.

“We are very interested to learn about how they will navigate the fragmented landscape and whether they will remain in the Simi Hills or eventually cross one or more freeways to the north or south,” said Jeff Sikich, biologist for Santa Monica Mountains National Recreation Area.

The blue-eyed, spotted kittens were around four and a half weeks of age and were marked with ear tags.

The National Park Service has been studying mountain lions in and around the Santa Monica Mountains since 2002.