The top photo is a typical vantage point for watching howlers. They present a challenge to photograph because usually they are seen when you are pointing the camera upward into a light sky background, and the monkeys, of course, are very dark. That produces a result like the first photo above.
To give you a better appreciation of howlers, I am posting the second photo of a howler up close. My wife took this photo while on a raft, although this was not taken in Tortuguero.
Howlers are appropriately named because they make an amazing noise. They travel in groups of about 6 in number, and the deep hoots or howls of a group can be heard a mile (1.6 km) away.
We had an unforgettable experience with howler monkeys in Tortoguero. Our room at the Tortuga Inn had screens for walls, as I will show in a few days. Each morning we had a group of howlers come by close to the room. It sounded as loud as a freight train coming through.