An Agouti is an aquatic, rabbit-sized rodent, like a small Capybara. They are common in many parts of Costa Rica.
The highlight of my trip to Palo Verde National Park was the sighting of this large Boa Constrictor at least 8ft long. One of my friends estimated it's length at 12ft. I know it was'nt that big.
Finding this snake was such a thrill, it's worth a second photo. It was crossing the road at dusk. I picked it up and put it on this tree branch to make it easier to photograph. It hissed loudly with open mouth, but never actually struck at me.