Marine Iguana

1 Overview

The marine iguana (Amblyrhynchus cristatus), also the Galapagos marine iguana or blunt-nose iguana, lives in the sea and also mangrove or swamp, feeding in the ocean. Found only in the Galapagos Islands. It is the only lizard that forages in the sea – swimming freely like a fish, drinking seawater and eating marine algae.

CONSERVATION NOTE: endemic to the Galapagos; protected. This is a specialist, cold-water marine lizard – not a typical pet.

2 Appearance

Looks like a dinosaur, 2-3 ft as an adult, lazy-looking, often on rocky beaches, usually black with a salt-encrusted head. Not always black – juveniles paler; breeding males on southern islands turn red and green; Santa Cruz ones brick-red and black; Fernandina ones brick-red and dark green.

Size varies by island: Fernandina and Isabella have the largest; Genovesa the smallest. Adult males about 1.3 m and 1.5 kg, females 0.6 m. Awkward on land but agile in water, swimming with a strong tail. Seven forms across the islands; Espanola males show red, yellow and black bands, green legs, feet and crest, while other islands’ iguanas are plain green or yellow.

Long sharp claws grip rocks against surf and crawl on seabed in currents to feed. Tail nearly twice the torso length, powering swimming. The ‘dirty snot’ is actually expelled salt.

3 Habitat & Environment

Because it lives in seawater, it depends heavily on sun; black skin aids heat absorption. Slow on land, so it bluffs to deter threats. Lives in coastal volcanic rocks; the most sea-adapted lizard. Galapagos is a cold-current region, so it must bask to raise body temperature before short dives to feed; after surfacing it basks again. Females fight for nesting sites; 2-3 eggs per clutch.

It eats algae and attached molluscs on reefs; has a salt gland in the nose that separates excess salt while chewing, expelled by ‘sneezing’ white crystals. To dive it slows circulation (seawater about 20 C is below its body temperature).

4 Care & Feeding

A remarkable animal; when threatened, its bulk makes it slow. Interestingly it auto-regulates heart rate – slowing underwater, speeding at surface; sensing a shark it can stop the heart to avoid detection. Usually dark grey; courting males turn grey to black with red spots.