cristatus; the only marine lizard in the
Marine iguanas are generally
gray to black in color, but males may develop
blotches of coppery green and red during the
mating season. The extent and vibrancy of those
colors varies from island to island. Juveniles
usually have a light-colored dorsal stripe. A
nasal gland filters its blood for excess salt
ingested while eating, which is expelled through
the nostrils, often leaving white patches of salt
on its face.
Built for marine life, the
marine iguana lacks agility on land but is
a graceful swimmer. Its laterally flattened tail
and spiky dorsal fins aid in propulsion, while
its long, sharp claws allow it to hold onto rocks
in strong currents.
Marine iguanas vary in body size, which is
different depending on the island the individual
iguana inhabits. The largest reach a length of
about 3 feet and weight of about 3 pounds. Males
are up to 70 percent larger than females.
Distribution and Habitat
Marine iguanas are only found on the Galapagos
Islands. They are most commonly found on rocky
shores, but have been seen in marshes and on
mangrove beaches. Each individual island has its
own subspecies, with size being the most
conspicuous difference between each subspecies.
Marine iguanas feed almost exclusively on
marine algae. During high low tides, green algae,
which is usually avoided, is eaten more often
since the usual red algae is not available.
Usually, however, the 4-5 red algal species are
the food of choice for marine iguanas.
Larger members of the species feed more often
by diving at high tide, while smaller animals are
restricted to intertidal feeding at low tide.
Average dive depth is 5 to 15 feet, but dives of
50 feet have been recorded. Since the waters
around the Galapagos Island are usually
relatively cold, most dives only last a few
minutes, but marine iguanas have been observed
staying submerged for more than half an hour when
the water is warm.
Breeding season runs from December into March.
Males are selected by females on the basis of
their body size, with larger males being
preferred. Mating territories are established and
defended by males.
About a month after mating, the female lays
1-6 eggs in a burrow dug 12-32 inches deep into
sand or volcanic ash up to 1,000 feet inland. She
guards the burrow for several days before leaving
the eggs to finish incubation, which takes about
95 days. Hatchlings are on their own from the
beginning, and usually scramble for cover
imediately after leaving the burrow.
Females reach sexual maturity at 3-5 years,
males at 6-8 years. Average lifespan in the wild
has not been recorded.
Other Behaviors and
The marine iguana regulates its body
temperature by alternating from cold ocean water
to basking on rocks near shore. It is active
during the day and spends the first few hours
after sunrise basking in the sun in preparation
for activity. When their body temperature is low,
these animals move more sluggishly and are
therefore at greater risk of predators. To
counter this vulnerability, the marine iguana
displays a highly aggressive behavior to bluff
its way to escape.
The Marine Iguana is currently labeled as
vulnerable in its conservation status. Since the
Galapagos Islands do not naturally have many
predators, the animals that live there never
developed the defenses needed to help protect
them against new enemies. This lack of
development makes them more vulnerable to attack
and becoming ill due to new bacteria as these
islands attract more and more people and animals
from different parts of the world.
genus & species Amblyrhynchus cristatus
Animal Diversity Web http://animaldiversity.org/accounts/Amblyrhynchus_cristatus/
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