Learn about keystone species and the Gorongosa lion mystery in this clip from Gorongosa Park: Rebirth of Paradise. After a decade of work by the restoration team, many of the original animal species have rebounded to impressive numbers. Its unclear if the lions have recovered too. The mystery: with so much prey to eat, why is Gorongosa's lion population not growing as fast as it should? Because lions are an important keystone species in the ecosystem, and a big draw for tourists, their recovery is critical to the success of the entire restoration effort.