Generally speaking, my photos of howler monkeys stink. They always look like dark lumps away up high in the shady branches of a tree. Alan's image, on the other hand, is really superb. He's got this male howler monkey, taken at Chan Chich Lodge, in full-blown howl, in lovely light. It's so vivid, you can almost hear the call.
I have searched in vain to find an audio of the Black Howler Monkey, Aloutta pigra, on line and have yet to find it -- sorry! If any Belize Field Notes readers find one, could you please post the link in Comments? It's such an amazing call, it would be great to share it here.