This is really an image intended to show the canopy from the top of a kapok tree, late in the day just before a thunderstorm (the Napo River is just visible as well), but it turns out that there are howler monkeys in the distance. Pretty much dead centre, on the top of a tree, there are some reddish brown blobs: that is a troop of howler monkeys. Trust me. I swear.

They are fairly relaxed critters, and are never more active than they need to be. We first heard them without realizing what they were: they sound like trucks passing on the highway in the distance. But there aren't any highways out there.... The sound carries for kilometers.