Fig. 2

Video analysis outputs from one imaging session of one orangutan (Pongo pygmaeus x Pongo abelii) focusing on three different locations. All videos were magnified 40 × and had the narrow bandpass (1 – 2 Hz) applied. A is the output from analyzing a spot on the chest (marked with the white box) with more fur, which produces no signal. The dominant peak here is probably due to animal movement. The shoulder (B) and wrist (C) produce the same output, taken to be HR. The stethoscope reading was 102 bpm