Legendary chimpanzee researcher Jane Goodall has died, the conservation organization she founded announced on Oct. 1.

Goodall, 91, died due to natural causes while she was in California on a cross-country speaking tour, according to The Jane Goodall Institute.

"Dr. Goodall’s discoveries as an ethologist revolutionized science, and she was a tireless advocate for the protection and restoration of our natural world," the institute said in statement on social media.

The British ethologist – a scientist who studies animal behavior within their habitat – had no formal training when she embarked on a study of chimpanzees in what would become Gombe Stream National Park in Tanzania, Africa, in the early 1960s. She skyrocketed to fame thanks in part to a National Geographic documentary about her field work and used her science celebrity status to advance conservation efforts for chimpanzees and other endangered species through her eponymous foundation.

"I passionately care about the natural world of which we are a part and which we depend. I love it," Goodall told USA TODAY in 2021. "I passionately care about animals. I want to fight the fact that many are becoming extinct and I want to fight the cruelty."