Mantled Howler Monkey 

(Alouatta palliata)  Order: Primates  Family: Atelidae
 

We saw Howlers high up the trees pretending to be branches or so it seemed - they moved so little.   In fact, they are characaterized as the least active of the monkeys, spending most of their time resting in the the tree's canopy.  In the photo above, you see the leg of a squirrel monkey.  In the photo below, the squirrel monkey has moved further along in the tree tops, but the Howlers are still in the same position.  They need to hold on to branches with two hands or a hand and a tail.  They move quadrapedally and do not swing from branch to branch as do orangutans.