All lions face high mortality as cubs, for a variety of reasons, including injuries, lack of food, illness and being killed by adult lions — more on that later. But when male lions begin to reach sexual maturity around age 2, the older males within the pride kick them out, Dereck said. The female lions, which are usually all related to some degree, typically stay behind.

For a young male, "the betrayal by his own blood must be confusing to him, but this is an ancient rite — the casting out of young males into a world of unknowns — a world where he will be able make it, or die," said Dereck, 57, who sports a white beard and looks every bit the wilderness gentleman. Dereck and Beverly, 56, seem to belong here in Duba, where they made other films about lions, including "The Last Lions" and "Relentless Enemies."