Biologists found a litter of four mountain lion kittens in the mountains of Southern California earlier this month, the National Park Service (NPS) said on Tuesday.

In a bid to track their movement, researchers attached ear tags to the four female kittens; P-66, P-67, P-68, and P-69. They also took tissue samples and gave the wildcats a health check.

Researchers are working to better understand how the mountain lions have survived, but also, whether they will be able to adapt as the areas surrounding their home in the Santa Monica Mountains see more development and urbanization.

One of four mountain lion kittens in their den in Simi Hills, Southern California, on June 11, 2018. (National Park Service [Public Domain] via Flickr)According to a NPS report (pdf), mountain lions in Southern California struggle to move freely between different areas of the wilderness due to the freeways that divide the landscape. This has resulted in problems like inbreeding and reduced genetic diversity in the existing populations, the report stated.

Mountain lions have died while trying to cross the freeway, and only nine attempts to cross the freeway in the past 16 years have been successful, the NPS says.

There is currently a bridge that would allow a wildlife crossing to be built below road level, but it would pose a danger to the homeless people that live under the bridge if the top predators were to come into contact with them, the LA Times reported.

The report recommended two locations where NPS believe wildlife crossing sites would be effective and allow mountain lions to cross safely between the fragmented parts of their once-connected habitat, without the risk of getting killed on the freeway.

If built, the crossings could help the isolated communities of 10 to 15 mountain lions across the Simi Hills, Santa Susana Mountains, and Los Padres National Forest interact and breed.

Watch Next:

Massive Colony of Penguins Discovered on Antarctica’s Danger Islands. It Changes Everything

So how did 1.5 million birds seemingly go unnoticed all this time?