Male orangutan (Pongo pygmaeus wurmbii) at Tanjung Puting National Park, Indonesia. Flanged adult male orangutans are the most solitary of all orangutan age/sex classes. Orangutans are more solitary than other apes. Males are loners. As they move through the forest they make plenty of rumbling, howling calls to ensure that they stay out of each other's way. The “long call” can be heard 1.2 miles away.