Caiman lizards are highly aquatic, and usually seen basking on logs or branches in a river or along a river's edge. We had hoped to see one on our boat trip from Iquitos to Madre Selva, and I was disappointed that we did not (well, probably did not — we caught a glimpse of some largish lizard on a floating log that might have been a caiman lizard, but that doesn't count).

Imagine our surprise when, on our first full day at the Madre Selva field station, Matt Cage and I glanced up while walking back up the hill from the dining area and saw this monster lizard lumbering across the grounds. Matt made a leap for it, but the lizard put on a burst of speed and disappeared into a small patch of jungle vegetation. Matt called for reinforcements, and in a few minutes five or six of us had the beast more or less surrounded. A few minutes after that it tried to bolt for freedom but was nabbed by one of the crew. We kept it around for a few hours and took many pictures before releasing it into the river.

Caiman lizards feed primarily on thick-shelled aquatic snails, and have massive, powerful jaws for crushing said snails. So it's a darn good thing that this one didn't bite anyone.

Here is a complete list of the herps I saw in the wild on my 2013 MT Amazon Expeditions trip.