When Daniel the orangutan arrived at the Phoenix Zoo in Arizona, he was in rough shape.

He was suffering from a respiratory disease, which, just like in humans, can worsen and even lead to death when untreated.

The stakes were high, especially considering that orangutans are a highly endangered species. And respiratory illnesses can be even more dangerous for orangutans which have an inflatable air sac that can be vulnerable when it becomes infected. Located in their throats, these air sacs are helpful in allowing orangutans to sustain the loud calls they're known for by creating a chamber for the sound to resonate within, but these air sacs are also prone to infection.