Aquatic post-escape behavior of the green iguana on Tobago

Green iguanas are well known for diving into streams from arboreal basking sites, but their behavior under water after the escape has to my knowledge not been reported, other than they swim away. While hiking in the Hillsborough River on Tobago on the morning of  7 June a one meter (total length) green iguana (Iguana iguana) dove into the river as we approached. After looking around the area for about 10 minutes I returned to the area where the iguana had been seen. Walking the shoreline the green and black bands of an iguana tail were visible underwater and upon closer inspection the lizard was lying on the bottom of the stream (about 40 cm deep) slightly under the bank and some floating roots. The lizard was less than 15 meters from its original point of entry into the stream. The lizard did not surface or move during  10 minutes  of observation. Several photographs were taken, and then I waded into the water and approached the lizard, for more photographs. During this time the iguana flicked its head several times in response to a crayfish that was touching its nose, but it did not respond to my presence even when I was less than half a meter from it, and bent directly over the lizard for more photographs. When two students approached on land, a leaf had drifted over the lizard's head and so they could also view and photography the lizard I reached into the water within a few centimeters of the head and removed the leaf. Again the lizard did not respond to my presence. Only when one of the students slipped in the stream did the lizard move, and it slowly swam away. Like many cryptically colored species, the green iguana relies on its camouflage to avoid predation underwater, but not in arboreal or terrestrial situations.

The submerged green iguana relying on its coloration to avoid detection. JCM

Close-up of the submerged lizard's crown. JCM