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Introduced Species in Galapagos

Ask any Galápagos guide or park ranger, and they’ll tell you that the most serious problem currently facing the islands is the threat posed by introduced species. The animals that live in Galapagos have been there by themselves for centuries, allowing them to adapt to very specific island conditions. Some scientists estimate that if it were not for humans, one new species would arrive to Galapagos “naturally” once every hundred years.

But the presence of humans changed all that. Since the islands were first discovered in the sixteenth century, dozens of new species have been brought to the islands. Some of them were brought accidentally, like the tree frog (Scinax quinquefasciatus) or the ship rat (Rattus rattus), but many, such as goats and pigs, were brought intentionally. In centuries past, sailing ships such as pirates and whalers would often release goats, pigs and other animals on islands so that they could be hunted for food on return visits. Also, early settlers brought cats, dogs, donkeys and other domestic animals with them, which would often escape into the wild.

The damage wrought by these animals is tremendous. Introducing new animals into a closed ecosystem often greatly disrupts it. Take for example the endemic Galapagos Flightless Cormorant. It arrived ages ago to the islands and began evolving. Most cormorants around the world can fly and make their nests in trees or on cliffs: the Galapagos variety does not fly and makes only a rudimentary nest of twigs on the ground. These adaptations were possible because the Galapagos cormorants have only one natural predator: the Galapagos Hawk, which can occasionally snatch a juvenile cormorant if the parent is inattentive.

But when cats, dogs and rats were suddenly introduced, the cormorant, nesting on the ground and incapable of flying away, suddenly became vulnerable. Although the cormorant populations on the islands are not in any immediate danger, there is no doubt that their numbers are reduced from where they were before man arrived.

Almost every introduced species has caused great damage in the islands. Goats, one of the worst offenders, can pick an area clean of vegetation, leaving slower tortoises and iguanas to stave. Aggressive introduced rats have muscled out the timid Galapagos Rice Rat. Cats eat bird eggs, small iguanas, snakes, lava lizards and birds. Even introduced birds such as the Smooth-billed Ani carry diseases which infect local species.

Many invertebrates have arrived in Galapagos as well, including fire ants, wasps and the Cottony Cushioned Scale (Icerya purchasi). The scale insect was doing so much damage to the mangroves that the ladybug was intentionally introduced simply to combat it.


Many visitors assume that the introduced animal species are the most harmful to the islands, but this is not the case: introduced plants have been taking over the islands at an alarming rate, elbowing out native plants in the process. Most of the plants were brought for a reason, such as blackberries or the Red Quinine tree, which produces an anti-malarial medicine. These plants are extremely difficult to control or eradicate: it is easier to remove goats or even rats from an island than an invasive plant species.

How To Help

The various institutions that are in charge of the ecology of Galapagos, such as the national park and the Charles Darwin Foundation are working aggressively to remove these invasive species and un-do the damage they have caused. There have been some success stories: feral donkeys, for example, have been eliminated from the islands. Project Isabela, a ten-year, multimillion-dollar initiative, removed an estimated 130,000 goats from Santiago and northern Isabela. Next up: cats, rats and certain plant species, including the Red Quinine.

As important as eradication, of course, is controlling the arrival of new species to the islands. Airplane cargo holds are fumigated, fresh food is not allowed, and carry-on baggage can be inspected. The Galapagos Islands are probably about the only place in the post-9/11 world where airport personnel are more concerned with people carrying pears and apples on board than bombs!

So do your part: be sure to follow the clearly posted restrictions when you visit the Galapagos, so that they can be preserved forever just as they are.

Here are some related tips to help plan your trip to The Galápagos Islands: Spotted Eagle Ray, Pink Iguana, Parrot Fish, Punta Cormorant - Floreana Visitor Site, Recommended Reading List, Land Iguana, Galapágos Penguin, White-Tail Damselfish, Shore Birds - Galapagos and Day Trips in Galapagos.

By Christopher Minster
I am a writer and editor at V!VA Travel guides here in Quito, where I specialize in adding quality content to the site and also in spooky things like...
02 Dec 2009

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