Wild orangutans also nap to make up for lost sleep, according to new research on an orangutan population in Indonesia. Yet despite the lost sleep, orangutans still often choose to build their nightly nests in close proximity to each other. For every additional, so-called association partner nesting nearby, an orangutan’s sleep period was about 14 minutes shorter. “As it gets colder at night they sleep less, and as it gets hotter during the day they sleep less. The study authors were unable to measure the orangutans’ sleep directly, relying instead on the proxy of nest time.