Invasive Species of the Galapagos Islands
by Daryl E. Vogel

The Giant Tortoises the Galapagos are so famous for were nearly extinct due to goats eating all the vegetation on the islands.
The Galapagos islands are a great place, but invasive species are destroying it. Invasive species are any non-native species that are detrimental to the environment. There are lots of invasive species in the Galapagos.

Goats came onto the islands a couple centuries ago. It is guessed that pirates brought them as a source of food. In 1997 it was estimated that there were between 100,000 and 150,000 goats in about 250,000 km2. They are harmful because in large groups they:

  • can cause erosion
  • eat the plants
  • eat the food native animals need
  • are hard to stop because they reproduce quickly

Goats eat all but two types of plants so the animals that rely on those plants will starve. Goats have one or two babies a year. If the goats aren't stopped they could eat all the plants in the area and drink all the fresh water so the plants can't grow back. Slowly the vegetation would disappear and some might plants could become extinct. If that happened:

  • species that rely on those plants would starve
  • the islands could have less than 25% of the species it has now
  • more than 40% islands would erode due to lack of vegetation
  • there would be less tourists and so less money could be put into getting rid of the goats
  • people would lose jobs
  • the Galapagos would be one big desert

The only solution is to get all the goats off the islands. The strategy at the Galapagos is to pick 1 goat that can't live on it's own and give it a necklace with radar on it. They give it 1 or 2 months to find a herd and then track it down and eliminate all the other goats. They repeat the process until only the herd-needing goats are left and then they eliminate those ones too.

Fire ants are probably the most aggressive invertebrate in the Galapagos. They got onto the islands between 1910 and 1920. Maybe they escaped from boats. They were originally put onto Santa Cruz Island. Fire ants destroy the ecosystem because they attack other invertebrates and because they eat the plants. Scientists and workers on the Galapagos Islands are destroying the fire ants by luring them out to see their distribution and using poison to finish them off.

Cats were introduced by pirates in the end of the 17th century and they also may have been brought by some settlers. They may live alone but are mostly found in groups. Cats are extremely adaptable. They are mostly found on Santa Cruz and Baltra islands. Cats are destroying the environment by eating iguanas and other small animals. The conditions on Baltra island are helping scientists get rid of them:

  • Baltra does not have many people so there is not much chance of the cats being reintroduced
  • it is a small island
  • there are not many plants

To get rid of the cats, people look for tracks during the day. At night the people follow the tracks to find and get rid of the cats. The cats have now been reduced to almost none. By 2004 no cat was seen on Baltra. There has been a huge increase in iguanas since the cats were eliminated.

In 1982 the Cottony Cushion Scale was spotted in the Galapagos. It infests and kills many of native plants by eating the leaves so the plant can not perform photosynthesis. In 2002 the Australian ladybug (an enemy of the Cottony Cushion Scale) was released into the Galapagos to eliminate the scale insect. Before that many studies were made to make sure the ladybug didn't make the problem worse.

In an interview with Dr. Robert Benstead-Smith, Ex-Director of Darwin Research Station and board member of the Darwin Foundation, he told me about a "grub" which burrow into bird eggs and sucks out the insides. At this time, they are researching options for dealing with this grub.

So to review, there are many goats that eat all the vegetation. Fire ants attack other invertebrates. Cats eat small animals. Scale insects destroy trees and other plants. All of them are invasive species that harm the environment of the Galapagos Islands. Scientists are taking measures now to eliminate them.

Click here to read more things we've learned on our trans-America bike ride

 

 

The desert landscape in the Galapagos is very fragile.

 

Now that goats have been eliminated, the turtles have made a remarkable comeback.

 

 

 

Thousands of visitors arrive in the Galapagos every year to see the unique animals.

 

Cats used to eat the marine iguanas, but are no longer the threat they used to be.

 

 

 

Marine iguanas have evolved from their ancestors on the mainland.

 

They are black to blend in with the volcanic rocks, they have strong tails for swimming, and eat sea algae..