The only lizard that forages in the sea, grazing algae on shallow rock.
The only lizard that forages in the sea, and the animal that most defines the Galapagos underwater even though it is barely a diving subject.
Adults graze algae from shallow rock. Large males feed subtidally and can stay down for several minutes at a few metres; most individuals, and almost all females and juveniles, feed in the intertidal and never submerge properly. The result is that this is a snorkelling animal, or a safety-stop animal, rather than one met on a dive.
Body temperature falls quickly in the water, which limits foraging time and is why an iguana returning to the rock will lie still in the sun for a long period afterwards.
Populations crash in strong El Niño years, when the green and red algae they feed on are replaced by a brown alga they digest poorly. Recovery has followed each recorded event, but the pattern is the clearest example of ENSO effects a visitor can actually watch.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.