Species: Pygathrix nemaeus
Also known as the Red-shanked Douc Langur…
The species Pygathrix nemaeus is actually composed of three subspecies. The red-shanked douc Langur, the black-shanked douc langur (P. nemaeus nigripes) and the grey-shanked douc langur (P. nemaeus cinerea). They are found in Vietnam and Cambodia and reside in tropical rain forests. They are an aboreal species and leaves constitute approximately 80% of their diet. In order to process the leaves they have a sacculated stomach containing bacteria to break down the cellulose. They them use RNASE1B to break down the bacteria. RNASE1B evolved via a duplication of pancreatic RNASE1 and contains several mutations that allow it to work more efficiently in acidic conditions of the stomach. The duplication event occured about four million years ago.
Red-shanked douc langurs are a diurnal species and travel in groups of 4-14, although they have been found in groups as large as 50. The groups tend to be multi-male multi-female with each having their own dominance hierarchy.
For more info go here (pdf) and here.