Bezzzman
Marine Iguanas
Just about every rocky shoreline in the Galapagos Islands is home to the marine iguana (Amblyrhynchus cristatus), the only sea-going lizard in the world. The marine iguana is an extraordinary animal that lives on land but feeds in the sea, grazing on a variety of seaweed – on exposed rocks, in subtidal areas, or by diving deeper into the cold seawater. This habit, totally unique in iguanas and in fact all lizard species of the world, provides them with an abundant food source. However, they cannot withstand the cold temperatures of the sea for too long and must pull out on land to warm up.Marine iguanas also mate and nest on land. While they have few predators in the sea, on land, young iguanas fall prey to hawks, herons, and other birds. Predation by introduced cats has had a major impact on many populations. Found throughout the islands, concentrations of up to 4,500 individuals per mile are not uncommon in some areas. The total population has been estimated at between 200,000 and 300,000.
The short, blunt nose is well-adapted to feeding on algae growing on rocks. The flattened tail is perfect for swimming, propelling the iguana through the water while its legs hang useless at its sides. Iguanas rid themselves of excess salt, consumed along with the algae, by a special gland connected to their nostrils. Marine iguanas are an excellent example of a species well-adapted and continuing to adapt to their environment. While marine iguanas feed mainly on algae, they have also been known to consume crustaceans and grasshoppers. On one or two islands, a small percentage of marine iguanas have been observed feeding on terrestrial vegetation, perhaps an adaptation to the near complete absence of nutritional sea algae during strong El Niño events.
When marine iguanas go hungry, they don’t just become thinner, they get shorter too. A scientist recently found that in times of El Niño-induced famine, the marine iguanas will shrink in length and then regrow as food becomes plentiful again. This finding, reported in the scientific journal Nature, is the first of a shrinking adult vertebrate. The adult iguanas can switch between growth and shrinkage repeatedly throughout their lifetime – a perfect adaptation to the boom and bust cycles in Galapagos associated with El Niño. The researchers postulate that bone absorption accounts for much of the reduction, with iguanas literally digesting part of their bones to survive.
Marine iguanas show their color as they mature – the young are black, while adults range from red and black, to black, green, red and grey, depending on the island, with Española marine iguanas being the most colorful of all, and earning them the nickname “Christmas Iguanas.” Marine iguanas become more colorful in the breeding season, at which time males defend territories on land where they mate with the females, who then lay their eggs in burrows. Marine iguanas lay 2 to 3 large eggs, which hatch between 2 ½ and 4 months later. Marine iguanas are known to live up to 60 years.
Marine Iguanas
Just about every rocky shoreline in the Galapagos Islands is home to the marine iguana (Amblyrhynchus cristatus), the only sea-going lizard in the world. The marine iguana is an extraordinary animal that lives on land but feeds in the sea, grazing on a variety of seaweed – on exposed rocks, in subtidal areas, or by diving deeper into the cold seawater. This habit, totally unique in iguanas and in fact all lizard species of the world, provides them with an abundant food source. However, they cannot withstand the cold temperatures of the sea for too long and must pull out on land to warm up.Marine iguanas also mate and nest on land. While they have few predators in the sea, on land, young iguanas fall prey to hawks, herons, and other birds. Predation by introduced cats has had a major impact on many populations. Found throughout the islands, concentrations of up to 4,500 individuals per mile are not uncommon in some areas. The total population has been estimated at between 200,000 and 300,000.
The short, blunt nose is well-adapted to feeding on algae growing on rocks. The flattened tail is perfect for swimming, propelling the iguana through the water while its legs hang useless at its sides. Iguanas rid themselves of excess salt, consumed along with the algae, by a special gland connected to their nostrils. Marine iguanas are an excellent example of a species well-adapted and continuing to adapt to their environment. While marine iguanas feed mainly on algae, they have also been known to consume crustaceans and grasshoppers. On one or two islands, a small percentage of marine iguanas have been observed feeding on terrestrial vegetation, perhaps an adaptation to the near complete absence of nutritional sea algae during strong El Niño events.
When marine iguanas go hungry, they don’t just become thinner, they get shorter too. A scientist recently found that in times of El Niño-induced famine, the marine iguanas will shrink in length and then regrow as food becomes plentiful again. This finding, reported in the scientific journal Nature, is the first of a shrinking adult vertebrate. The adult iguanas can switch between growth and shrinkage repeatedly throughout their lifetime – a perfect adaptation to the boom and bust cycles in Galapagos associated with El Niño. The researchers postulate that bone absorption accounts for much of the reduction, with iguanas literally digesting part of their bones to survive.
Marine iguanas show their color as they mature – the young are black, while adults range from red and black, to black, green, red and grey, depending on the island, with Española marine iguanas being the most colorful of all, and earning them the nickname “Christmas Iguanas.” Marine iguanas become more colorful in the breeding season, at which time males defend territories on land where they mate with the females, who then lay their eggs in burrows. Marine iguanas lay 2 to 3 large eggs, which hatch between 2 ½ and 4 months later. Marine iguanas are known to live up to 60 years.