The Arrival of Native Species in the Galapagos Islands
Today, most scientists accept the theory of long-distance dispersal for bringing life to the Galapagos Islands. It is hard to imagine that so many organisms could endure the hazardous voyage, survive in an unfamiliar environment and reproduce. Flotation rafts of natural vegetation, wind and air currents and oceanic drift all contributed to this “sweepstakes dispersal.” Birds displaced from their migratory routes also landed on the islands. Sea birds carried seeds and invertebrates on their feathers and in their digestive tracts. When they deposited this “cargo,” new colonies took root.
Many animals are not found in the Galapagos. Amphibians and other aquatic animals, for example, are poorly represented. Large terrestrial mammals also failed to make the crossing. The lack of herbivorous mammals left a niche open for tortoises. These huge reptiles developed and became the large grazing herbivores on land—a position they enjoyed until the relatively recent arrival of humans with domestic livestock.