I spent a few days in Yaxha and Tikal region of Guatemala in Dec-Jan of 2008 and 2009.
I stayed in an ecolodge, Hotel Sombrero. It was a quiet, rustic location away from the crowd in a private wooded area. First morning I wanted to be up early and be out recording, but I felt I was hearing rain, so decided to sleep longer. All of a sudden as the dawn was breaking I heard the heart tearing sound. Immediately realized that howlers are just in a nearby tree. I quickly set up my recorder and lied down on the bed listening to them without any movement.
I presume alpha male was the one who first woke up. I could hear him taking deep breath and then pouring all that air out with some additional energy. I could almost feel that he has a large lung. As he woke up his sound became louder and louder. He went on for more than ten minutes. Almost at the end others joined him. His sound was so loud that the dawn chorus of other birds were drowned in howls of Howler.
Next day evening I decided to take a walk to Sombrero ruins that was on the hotel property. As I started the walk, I could hear the howlers in some distance. When I reached the gully and stood for sometime, I heard two groups of howlers calling one after the other. It was very eerie and scary. Initially, I thought it was I who was the cause of the commotion, but it went on. If it was in India and monkeys were calling then I would have thought a leopard or a tiger was in the vicinity and that agitated the monkeys. So here I thought may be a puma or a jaguarundi was on the prowl. I continued my walk with a bit of hesitation to make sure that there are no carnivores in the vicinity. I listened for their sounds and tried to smell for carnivore. After half an hour I reached the spot where the monkeys were. My arrival further agitated two of the howlers that looked like an adult and a teenager. Both howled at me. They would take deep breath and let out the howls. After about 20 minutes of watching, recording and listening I decided to walk ahead to a quieter place to listen to birds. Somehow my gut feeling made me a bit uneasy about what was around me. May be it is just the jungle sense I have picked up in India. Also, it was getting late and was not sure how much I had to walk, so I increased my pace. Once I reached the path, which was parallel to road, I felt better to slow down.
It was a great experience to listen to these large lunged giants!