"I wish I could have stayed longer as he probably would have taken a full family album."
The crested black macaque is extremely rare and critically endangered. These belonged to a study group near a science base in the region, home to researchers from Holland.
David added: "I teamed up with a local guide because I knew about the apes and wanted to photograph them.
"I walked with them for about three days in a row. They befriended us and showed absolutely no aggression - they were just interested in the things I was carrying.
"They aren't known for being particularly clever like chimps, just inquisitive.
"Despite probably never having any contact with humans before they didn't feel threatened by our presence, and that's why I could walk with them during the day."