Los Angeles, California, July 30, 2008—Piggyback rides! Glenda, a four-year-old gorilla, catches a lift from her mother, Rapunzel, at the Los Angeles Zoo.

Glenda and Rapunzel are western lowland gorillas, a critically endangered species native to Africa that has been hard hit by the bush meat trade and Ebola virus.

On Tuesday, researchers announced the discovery of 125,000 western lowland gorillas in the Republic of the Congo. If confirmed, it would more than double the world's estimated gorilla population.