Success! Our guide located a troop of howler monkeys This big guy seemed to be the dominant male of the troop Our guide made a throaty hooting call and the monkey answered back 
In the upper center is a mama with a baby We could see the baby moving from the ground but the picture doesn't have enough detail 
The big male is moving around in the tree and howling 
He jumped from one tree to another His arm is hanging on to the branch above him and his tail is drooping down and curled around the trunk below him 
The big guy is holding the branch above him with is left hand 
He is on the move again 
You can see the tan color of his rump 
I think there are 5 monkeys in this picture, 1 at the left center, 2 (mama & baby) a little higher and to the right of the 1st one, and 2 (mama & baby) toward the upper right corner |