Saturday, 8 August 2015
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Galapagos land iguana (Conolophus subcristatus)

There are two species of land iguana found in the Galapagos; this species Conolophus subcristatus, is found on six islands and Conolophus pallidus is found only on Santa Fe. This species is very large, growing to lengths of over a meter. The short head is blunt and the back legs are thick and powerful, with long sharp claws on the toes. It is yellowish in colour with blotches of white, black, rust and brown and a row of spines passes along the centre of the neck and back.

Galapagos land iguanas are active during the day. They maintain their body temperature by basking in the sun to warm up and seeking shade when they become too hot. In the morning they can be found basking, but during the heat of midday they tend to retreat into shade. At night they sleep in burrows which they dig themselves. This species is omnivorous but tends to mainly eat plants and the fruits and pads of cactus trees. They may remove the spines with their claws, and these cacti provide them with plenty of moisture during dry spells. This species has an interesting relationship with Galapagos finches; the iguanas often raise themselves from the ground and allow the finches to remove ticks from their bodies.

Males defend territories, with displays involving head bobbing, biting and tail thrashing. During courtship, males aggressively court the females. After mating, the females set off on a migration to suitable egg-laying habitat. On Ferdinanda Island, females are known to travel up to 15 km to reach a suitable nesting site. They then lay two to 20 eggs in a 50 cm deep burrow. The nest site is guarded for a number of days after laying, in order to prevent other females from laying in the same place and damaging the eggs. The young hatch after 85 to 110 days; it then takes them up to a week to dig their way out of the burrow. Maturity is reached between eight and 15 years. If they survive the first years of life, when they are most vulnerable to predation and food scarcity, land iguanas can live for up to 50 years.

Land iguanas are endemic to the Galapagos Islands off the coast of Ecuador. Conolophus subcristatus is native to six islands. In 1835 when Charles Darwin first went to the Galapagos, land iguanas were extremely numerous; he wrote: “I cannot give a more forcible proof of their number, then by stating that when we were left at Santiago Island, we could not for some time find a spot free from their burrows on which to pitch our single tent”. Sadly, this once thriving Santiago Island population has become completely extinct. This iguana lives in the drier areas of the islands on which they occur, in scrubby habitats. Females require access to areas of sandy or loose soil in which to lay their eggs; some females even use the ash around dormant volcanic craters.

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