A litter of four blue-eyed mountain lion kittens was found in the Simi Hills, a habitat between the Santa Monica and Santa Susana mountain ranges in California. All four kittens are female and have been named P-66, P-67, P-68 and P-69.

National Park Service researchers had been tracking the mother of the kittens — known as P-62 — since January. Biologists were able to locate the site of her den while she was away from her kittens. This is the first kitten den that researchers have documented in the Simi Hills area. They were found on a 2,669-acre site belonging to the Santa Susana Field Laboratory. (We've written about previous litters in the Santa Susana Mountains, but this is the first in this particular area.)

"This is the first litter we have marked at the den in the Simi Hills, which happens to be a critical habitat linkage between the Santa Monica Mountains and larger natural areas to the north," said Jeff Sikich, biologist for Santa Monica Mountains National Recreation Area. "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."

According to the NPS, because the Simi Hills are immediately north of the 101 Freeway, any animals moving north-south into or out of the Santa Monica mountains must pass through the area. Except for the mother of these kittens, every other mountain lion that biologists have tracked in the area has crossed either the 101 or 118 Freeway or both, offering key information about wildlife connectivity.

Mountain lion kitten P-69 is held by a National Park Service biologist. All the mountain lion kittens have bright blue eyes. (Photo: National Park Service)

After researchers noticed a series of localized GPS locations from the mother's radio collars, they suspected she might be in a den. Even with GPS information, however, it was difficult for biologists to find the location for the den because mothers choose areas that are hard to locate.

Once the kittens were discovered, NPS biologists checked their health, took tissue samples and marked them with ear tags. The kittens — who have blue eyes and spots — weighed between four and five pounds and were estimated to be around 4.5 weeks old.

This is the 15th litter of mountain lion kittens that NPS biologists have discovered and tagged at a den site since they began studying mountain lions in the area in 2002.

Mountain lion kitten known as P-68 discovers the outside world. Mountain lion kitten known as P-68 discovers the outside world. (Photo: National Park Service)

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.