The most recent Planet of the Apes trilogy is truly great cinema. As I was watching the most recent entry, I came to wonder why there are not many orangutans. The landscape is primarily lived upon by chimps and gorillas. Is there a story-specific reason for the perceived lack of orangutans or is it just coincidental?
The apes seen in the new Planet of the Apes trilogy were all present in the San Francisco area at the beginning of the series, or descended from those who were. We learn in the third film that the apes were not even aware that there were intelligent apes like them popping up elsewhere.
In Rise of the Planet of the Apes, we see Caesar spreading the virus that granted the apes intelligence in three main locations:
- Gen-Sys, a biotech company that tests on several apes.
- The San Francisco Zoo
- A nearby ape sanctuary
Gen-Sys tests on chimps (except for Koba), so they are the most common apes in the films. The sanctuary is predominantly bonobos and chimps, with only one gorilla and orangutan (Maurice). The zoo has more gorillas, bonobos, and chimps, but no orangutans (in real life, the San Francisco zoo also doesn't have orangutans).
So the simplest answer is that there aren't really many orangutans in the film because there were no orangutans in San Francisco at the time, except for an old abandoned circus performer. This makes sense: orangutans aren't pursued as pets and are almost never test subjects given how endangered they are.
Out-of-universe, the filmmakers likely wanted a distinctive-looking ape to serve as Caesar's chief advisor, the same reason Koba is given obvious scars. This is particularly helpful in the later films, when all the bonobos and chimps start to look alike.