Biologists in California got a holiday surprise last December—a pair of brand-new, blue-eyed mountain lion kittens peeking out of a den.

The team found the youngsters—whose picture was recently released by the National Park Service—while keeping tabs on a female named P-19 in the Santa Monica Mountains. Since 2002, the scientists have been using tracking devices, such as GPS collars, to study the behavior and movements of big cats living on the outskirts of Los Angeles.

While newborns are always cause for celebration, the kittens could be particularly important, depending on who the father is, says Jeff Sikich, biologist for Santa Monica Mountains National Recreation Area.

P-19’s previous two litters were both sired by her father, P-12,