The plant life of Galapagos is just as extraordinary as it’s animal life, although receiving less attention and publicity. Sadly, there are many threats facing the vegetation, and world attention is currently focused on raising funds for botany campaigns to safeguard endangered species and to control the many invasive plants introduced to the islands by humans. There are about 560 native species of plants in the islands. Of these, almost one third are endemic to the islands, meaning that they are found nowhere else on earth. For example, Galapagos has its very own endemic species of cotton, pepper, guava, passion fruit and tomato. One of the biggest problems in Galapagos comes from foreign plant species introduced to the islands by people, which then become pests and invade the native vegetation. Most of these species were brought intentionally either for agriculture or gardens, and the problem is therefore greatest on the inhabited islands.
The giant tortoise is probably the best known of all the Galapagos animals. This ancient creature has even given the archipelago it’s name; “Galapago” is the spanish word for tortoise and may be derived from the word for saddle, referring to the distinctive saddle-like shell of some of the tortoises. Galapagos giant tortoises can weigh up to 250 kg. and live for up to 200 years – or even more. It is likely that all the present species of giant tortoise evolved in Galapagos from a common ancestor that arrived from the mainland, floating on the ocean currents. Although this seems an incredible journey it is known that Galapagos tortoises can float easily in sea water. The original ancestor of the tortoises was probably of normal size and evolved into the present-day giants after its arrival in Galapagos. This is due to a phenomenon seen in many island ecosystems where gigantism evolves because there is no longer any need to hide from predators and because there are no other similar animals to compete with for food. Once the tortoises spread around the archipelago, they evolved on their isolated islands into the different races we see today, some with domed carapaces (shells), and others with saddle-back carapaces. Giant tortoises are active for much of the day, spending most of it feeding. They are vegetarian, eating a great variety of plants in large quantities. However, their digestive system is rather inefficient so much of the food passes through their body without being digested. At night they sleep, often in snug depressions in the ground which probably help conserve heat.
Just about every rocky shoreline in the Galapagos islands is home to the marine iguana, the only sea-going lizard in the world. The marine iguana is an extraordinary animal which lives on land but grazes on algae, growing either on exposed rocks or under the surface of the water, making it necessary for the iguana to dive into the cold seawater for feeding. This habit provides them with an abundant food source but can make them vulnerable to predation by sharks and other large fish. They are found throughout most of the archipelago, in coastal concentrations of up to 4,500 individuals per mile. The total population has been estimated at between 200,000 and 300,000.
There are two species of land iguana found in the Galapagos Islands – Conolophus subcristatus is native to six islands, and Conolophus pallidus is found only on the island of Santa Fe. These Santa Fe iguanas are large (over 1 metre long), yellowish animals, with males weighing up to 13 kilograms. Galapagos iguanas are thought to have had a common ancestor which floated out to the islands from the South American mainland on rafts of vegetation. They live in the drier areas of the islands and in the mornings are found sprawled beneath the hot equatorial sun. However, to escape the heat of the midday sun, they seek the shade of cactus, rocks, trees or other vegetation. At night they sleep in burrows dug in the ground, to conserve their body heat.
Of the 29 resident Galapagos land birds, 22 are endemic and all of them are thought to have colonised the islands from the South American mainland. Although largely dull in colour, they compensate by their extreme tameness. The Woodpecker finch is one of the few tool-using birds in the world. The Sharp-billed ground finch parasites seabirds by hopping on the backs of masked and red-footed boobies where they peck at the skin until they are able to drink their blood. The Galapagos islands harbour several avian predators, notably the buzzard-like Galapagos hawk, the fierce Galapagos short-eared owl and the barn owl – all three are endemic species.
The Galapagos islands are a mecca for tropical seabirds, of which there are 19 breeding species. Seven of these are endemic. The tropical seabirds found in the archipelago include: boobies, cormorants, pelicans, frigate birds, tropic birds, albatross, shearwaters, gulls and penguins. Some of these species are found on many islands, while others have tiny populations and are confined to certain parts of a single island. Each species has evolved its own behaviour patterns related to feeding and breeding, and in any month you will find some seabirds displaying, incubating eggs or feeding their young.