There are two endemic species of these large, yellowish lizards in the
Galápagos. One, Conolophus pallidus, lives only on Santa Fé. The other, Conolophus
subcristatus, has a more reddish-orange hue. It now lives on six of the islands:
Fernandina, Isabela, Santa Cruz, South Plaza, Baltra and Seymour. There were once so many
iguanas on Santiago that Darwin complained he could find nowhere to pitch his tent, as the
ground was undermined by burrows. Today they have all gone. On Baltra, too, the iguanas
disappeared during World War 11, when the island was occupied by the US military. Luckily
Captain Allan Hancock, a wealthy American industrialist, had transferred 72 individuals to
neighbouring Seymour in 1932 and so saved the race. Many have since been repatriated to
Baltra.
Adult land iguanas are vegetarian and eat mostly Opuntia cactus pads and fruits, spines
and all, either on the ground or on plants which droop to within reach of an iguana
standing on its hind legs. They also love flowers and readily cat those of the cacti
Sesuvium and Portulaca. Even visitors with any yellow on their person will attract these
lumbering reptiles. They also resort to eating carrion when available. Young iguanas begin
life eating various insects and arthropods before converting to vegetarianism.
Land iguanas seem to wear a permanent smile and have a rather dimwitted countenance.
However, once they have warmed up, their sprinting ability will take anyone by surprise.
Land iguanas and giant tortoises have developed a symbiotic relationship with some bird
species. When small and medium ground finches or mockingbirds land close to the iguanas or
tortoises, or on top of them, the reptiles adopt a bizarre erect posture. This allows the
birds unrestricted access to the reptiles' skin, to feed on body ticks and other
parasites. Marine iguanas have many fewer external parasites living in their watery
environment and do not assume this helpful posture, although birds may still remove their
parasites.
Large male land iguanas may reach 13kg and more than 1m in length. During breeding, males
establish heavily defended territories which overlap with those of up to seven females.
When a female becomes receptive she advertises the fact to the male by a raised posture
and head shaking, mates with him and disappears to an area suitable to lay her eggs. She
will dig a long burrow down to a damp area of soil and deposit up to 20 eggs in the
clutch; then aggressively defend her nesting chamber against other females, who are likely
to dig it up while looking for a place to deposit their own eggs.
Emerging hatchlings are roughly the size of lava lizards. They immediately come under
attack by hordes of predators. Hawks, owls, snakes and herons loiter around the nesting
area ready for the bonanza, not to mention a full gamut of
introduced mammals. Hatchlings which do survive reach sexual maturity at about 12 years of
age, and may go on to live to more than 60 years. Without doubt the two best places to
observe land iguanas are on the islands of South Plaza and Sante Fé, although the
reptiles may also readily be encountered at Urvina Bay and on the hike to Volcán Alcedo,
both on Isabela.
Text: Galápagos Wildlife a visitor's guide.
