Chimpanzee, gorilla, orangutan, and gibbons species cluster with human isolates. Among the rarer large mammals are the Sumatran rhinoceros, Sumatran tiger, Orangutan and Sumatran elephant. The hyena kills the zebra and later the orangutan. A male Sumatran orangutan was born at the zoo in November 2019. The Sumatran orangutan is endemic to the north of Sumatra. Great apes such as orangutan males seem to have facial hair as well. He has also campaigned for the Sumatran Orangutan Society. A number of orangutan rescue and rehabilitation projects operate in Borneo. He remains active in forest and orangutan conservation efforts in Indonesia. Galdikas reported that her cook was sexually assaulted by a captive male orangutan. Climate change is another threat to Bornean orangutan conservation. Pratchett was a trustee for Orangutan Foundation but was pessimistic about the animal's future. However, Caesar also befriends a former circus orangutan named Maurice, who also knows sign language. They found the different orangutan populations behaved differently. Cheryl D. Knott further investigated tool use in different wild orangutan populations.