Ernest, Evelyn, Marion and Miss Ellen, four cubs born at the San Diego Zoo in 2014, lived with their mother in "Lion Camp" before being introduced to their father, Izu. At Lion Camp, the cubs had visual access to their father, but no unprotected physical interaction was allowed until the cubs were four months old.
"It pretty much replicates what would happen in the wild," said Tony Franceschiello, a senior keeper at the Safari Park of the zoo. "[The mother] would go off and have her cubs on her own, and when they're old enough she brings them back to the pride and introduces them, and everyone is together."
On the morning that the cubs were released into the main habitat with their mother, Oshana, they immediately began exploring the new territory. Izu came out later; the cubs ran after him curiously but kept their distance until the adult male paused to look around... then one of them got up the courage to put its nose to one of Dad's hind legs for a sniff.
When Izu startled and grunted, throwing the cub an annoyed glanced, the cub immediately sat down submissively. A nearby sibling ran off, wanting no part of whatever came next.
The cubs' caution may be instinctive, as male lions are known to kill cubs that he believes are not his offspring. A male lion that has recently taken over a pride will kill the cubs that are already there, to ensure that the next generation of the pride belongs to him.
That's not to say that he can't be fooled, however. LionAid, a British organization, dedicated to the protection and conservation of lions, notes a number of ways that females protect their cubs from a new pride leader. For example, a female with newborn cubs might hide them then return to the pride and mate with the new male. Later, when she brings the slightly older cubs into the pride, they are accepted by the leader even though they are not, technically, his offspring.
Izu proved to be a tolerant dad if a very vocal one. He allowed the cubs to pounce on him playfully, roaring gently the entire time. When he tired of playtime, Izu got up and walked away, snorting and roaring as if to reestablish his tough guy image.