America's favourite big-city big cats have welcomed five kittens to their crew.

Two new litters of baby mountain lions were captured on video in the Santa Susana Mountains north of Los Angeles, the National Park Service said.

And, no surprise, they nailed their Hollywood-area debut with adorable hisses, deep blue eyes and darling little claws.

Five Mountain Lion Kittens Found

Last month was a big one for our mountain lion researchers. They found a total of five kittens in the Santa Susana Mountains! P-48 and P-49 were born to P-35. And P-50, P-51, and P-52 to P-39. In both cases, P-38 is suspected to be the father. It's great that our local big cats are reproducing, but these kittens will face challenges as they grow up, from roads to rat poison to males finding their own territory. - Ranger Zach

Posted by Santa Monica Mountains National Recreation Area on Wednesday, 6 July 2016

The discovery of the kittens is significant because LA's mountain lion population doesn't have it easy.

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Those in the Santa Monica Mountains, to the south, are hemmed in by multi-lane highways, which has prevented migration and led to an inbred population, and rodent poison is a regular threat.

One lonely lion known as P-22 has a big social media following but no lady lions to consort with.

Lions must also dodge cars near the kittens' home, the Santa Susanas, which are a key gateway connecting the animals with their brethren in the Santa Monicas and the Los Padres National Forest.

These mountain lion kittens are part of a litter of three, which biologists have dubbed P-50, P-51 and P-52. Photo / National Park Service
These mountain lion kittens are part of a litter of three, which biologists have dubbed P-50, P-51 and P-52. Photo / National Park Service

The kittens were captured and ear-tagged by the Park Service, which for 14 years has been studying how mountain lions in and around Los Angeles are coping with an urbanised and increasingly fragmented habitat.