Aniamals, Adaptation, and the Galapagos Islands Discover with Darwin
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Introducing... the Galápagos
What effects can animals have if they move to a new home?
Amy KL Borrell 

Can you imagine?

What might happen if you took animals out of their natural habitat and brought them to a new environment where they did not naturally occur? It’s possible not much would change, but it’s also possible — even probable — a whole lot would change as a result.

It’s hard to know how introducing new animals might change an environment. That species might breed successfully and then eat other animals and deplete a naturally occurring resource. A lot can change as a result of an introduced species.

In the Galápagos, early visitors and settlers brought domestic animals — and plants — with them to provide food and companionship, but the introduction of these species often had unintended consequences. Many of the introduced species became wild — or feral — and spread to inhabit many of the islands.

Because of the isolated nature of the islands, native animals and plants evolved few defenses against introduced species. That means native species — like the giant tortoises — are especially vulnerable to the effects of introduced species.

Some examples of introduced species on the Galápagos are:


  1. At one time there were probably 150,000 feral — or non-domesticated — goats on Albermarle (or Northern Isabela) Island.

  2. They were responsible for destroying much of the natural Galápagos giant tortoise habitat by feeding and trampling the island.

  3. Project Isabela was created to remove the goats and restore the natural biodiversity on the island.


  1. They are among the most ecologically destructive introduced animals in the Galápagos.

  2. They trample the nests of ground-nesting birds, giant tortoises, and sea turtles.

  3. They eat the bird, tortoise, and turtle eggs and at times compete with them for food.

Cats and Dogs

  1. These pets have become feral and threaten the populations of marine and land iguanas, lizards, tortoises, and birds.

  2. Cats feed on birds, lava lizards, and marine iguanas.

  3. Dogs eat turtle eggs, baby tortoises, and hunt iguanas.


  1. These pests probably first arrived on pirate boats or with settlers several centuries ago.

  2. Because they carry many human and animal diseases, rats have caused some of the biggest ecosystem damage of all the invasive species.

  3. Like goats and pigs, scientists hope to wipe out the rat population on the islands.


  1. Nearly 600 plant species have been introduced to the Galápagos by settlers and visitors.

  2. 90% of those have been deliberately introduced including vegetables, timber trees, medicinal plants, and ornamentals.
  3. One example: quinine and guava trees have taken over large areas of land, replacing native trees and creating newly shaded areas. The extra shade can kill smaller plants and eventually these trees can wipe out the vegetation around it.

  4. A few plants have been accidentally introduced including weeds that have spread widely.

What would you suggest as a solution for introduced species of animals and plants? How could efforts to solve the issue of introduced species potentially lead to new complications?
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