Number of orang-utans living in the USM forests estimated from the combination of ground and aerial surveys (See Figure 2 for the exact locations of the areas).

<p>Number of orang-utans living in the USM forests estimated from the combination of ground and aerial surveys (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011510#pone-0011510-g002" target="_blank">Figure 2</a> for the exact locations of the areas).