The Iguanas of Galapagos, Ecuador
The best-known of the 13 species of Iguanas is the common, or green, iguana, which occurs from Mexico southward to Brazil. Males of this species reach a maximum length of over 2 metres (6.6 feet) and 6 kg (13.2 pounds). It is often seen basking in the sun on the branches of trees overhanging water, into which it will plunge if disturbed. Food of the common iguana consists largely of leaves, buds, flowers, and fruits of fig trees (genus Ficus), although many other trees are also fed upon. Whereas this lizard has a well-developed digestive system housing bacteria that ferment plant material, it also eats invertebrates when young and has been known to eat small birds and mammals.
During the rainy season, males become territorial, and mating pairs are established. At the end of the rainy season, eggs are fertilized and then laid in clutches of 30 or 50 in the ground during the early dry season. After 70-105 days, the 7.6-cm- (3-inch-) long hatchlings emerge. During this time, eggs and young are vulnerable to predators such as coatis and other omnivores. Adult iguanas have been used as food by humans for thousands of years and are threatened by hunting and habitat loss. In rural areas they are a major source of protein. The closely related West Indian iguana lives on several Caribbean islands. Other well-known relatives are the rhinoceros iguana of Haiti, the desert iguana of Mexico and the USA, and the marine (Amblyrhynchus cristatus) and land (Conolophus) iguanas of the Galápagos Islands. [- Encyclopedia Britannica 2004]
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Excerpt from The Voyage of the Beagle (1831-36) by Charles Darwin The [marine iguana] is extremely common on all the islands [of Galapagos], and lives exclusively on the rocky sea beaches ... It is a hideous looking creature, of a dirty black colour, stupid, and sluggish in its movements. The usual length of a full grown one is about a yard, but there are some even four feet long ... Their tails are flattened sideways, and all four feet are partially webbed. They are occasionally seen some hundred yards from the shore, swimming about; and Captain Collnett, in his Voyage, says, "They go to sea in herds a-fishing, and sun themselves on the rocks; and may be called alligators in miniature." ... I opened the stomachs of several, and found them largely distended with minced sea-weed. [Its food and voluntary swimming out at sea] absolutely prove its aquatic habits; yet there is in this respect one strange anomaly, namely, that when frightened it will not enter the water ... They do not seem to have any notion of biting; but when much frightened they squirt a drop of fluid from each nostril. I threw one several times as far as I could, into a deep pool left by the retiring tide; but it invariably returned in a direct line to the spot where I stood. The
[land iguana] is confined to the central part of the archipelago ... I cannot
give a more forcible proof of their numbers, than by stating that when we were
left at James Island, we could not for some time find a spot free from their
burrows on which to pitch our single tent. Like their brothers of the sea-kind,
they are ugly animals ... from their low facial angle they have a singularly
stupid appearance ... In their movements they are lazy and half torpid. When not
frightened, they slowly crawl along with their tails and bellies dragging on the
ground. They often stop, and doze for a minute or two, with closed eyes and hind
legs spread out on the parched soil ... They inhabit burrows, which they
sometimes make between fragments of lava, but more generally on level patches of
the soft sandstone-like tuff. The holes do not appear to be very deep, and they
enter the ground at a small angle ... I watched one for a long time [making its
burrow], till half its body was buried; I then walked up and pulled it by the
tail; at this it was greatly astonished, and soon shuffled up to see what was
the matter; and then stared me in the face, as much as to say, "What made you
pull my tail ?" | |||
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