Galapagos endemic species
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Visitors to the Galapagos Islands will hear their guides talk about three different types of animals and plants. The terms used to describe them are endemic, native and introduced. What’s the difference?
Endemic animals are only found in Galapagos: the marine iguana is one example.
Native animals are found naturally in Galapagos and elsewhere: the Frigatebird is a good example. Introduced species are found in Galapagos because they were brought there by humans, intentionally or accidentally. The goat is an example of an introduced species.
For obvious reasons, it’s the endemic species that people come to see! Here’s the scoop on endemic Galapagos species.
How did endemic Animals arrive to Galapagos?
Every endemic Galapagos species took a different path to the islands ages ago. Animals such as iguanas, rice rats and tortoises are believed to have come from the South American mainland. The scenario is something like this: In a rough storm, some animals get flooded out of their homes and into a river, where they cling to a fallen tree or some other clump of vegetation. The river washes them out to sea, where they miraculously survive until they wash up on the shores of Galapagos.
On the other hand, birds and bats could, of course, fly to the islands. Larger, flightless animals like sea lions and penguins likely arrived on the islands having drifted away from their homes in storms.
Why are there so many endemic reptiles and so few endemic mammals?
The answer has to do with how hard it is to get to Galapagos. A reptile, like a snake or a lizard, needs much less food and water than a mammal (at least short-term) and is less sensitive to strong sunshine. Because Galapagos is so far away from the mainland, only the most fit species can survive the journey. Once on the island, the reptiles took the environmental niches usually reserved for mammals: giant tortoises are large herbivores because animals like goats and horses do not naturally exist there.
What do endemic species have to do with evolution?
Endemic species are ones that evolved from something else. Take the marine iguana. Ages ago, some South American iguanas were washed out to Galapagos somehow. South American iguanas generally live in trees, eat plants and do not swim unless they have to. Once on the islands, the iguanas came out of the trees, developed the ability to swim and hold their breath and now eat algae.
Another good example is the 13 species of Finch, all of whom descended from a common ancestor. Each finch evolved to fill an available environmental niche on different islands. Similarly, the Galapagos Giant Tortoise evolved uniquely to different islands. Charles Darwin’s careful observation of these species led to his renowned Theory of Evolution.