Figure 1

(A) Photographic frequency (including different camera-trap placement categories) and (B) probability of orangutans coming to the ground for six different forest classes ordered from primary to recently heavily logged forest (PRIM = primary forest; VOL = very old conventionally logged forest >20 years ago; RIL-OLD = reduced impact logging 2–20 years ago; CL-old = conventional logging 2–20 years ago; RIL-REC = reduced impact logging within the last 2 years; RIL-REC = conventional logging in the last 2 years). (C) Relationship of photographic frequency (black) and probability of orangutans coming to the ground (red) with orangutan density, plotted for primary forest, but patterns for other forest classes are equivalent.