Galapagos Islands

The Galapagos Islands

Christy Bosley

Axia College of University of Phoenix

SCI 230

Angela Buffington

March 16, 2008

The Galapagos Islands

The Archipelago de Colon is better known as the Galapagos Islands, who got their name from the Spanish word galapago. This word means “saddle” and refers to the shells of one of the islands’ most famous inhabitants, the Galapagos Giant Tortoise (Wikipedia, n.d.). The Galapagos Islands are a group of volcanic islands located about six hundred miles from Ecuador in the Pacific Ocean. This series of islands was the very first World Heritage Site chosen by the United Nations Educational, Scientific, and Cultural Organization, UNESCO (Nelson, 2007).

An excellent example of this “adaptive radiation” is Darwin’s Finches. In fact, it was his study of these birds which led Charles Darwin to describe this phenomenon. As Darwin explored the Galapagos while on board the survey ship HMS Beagle, he noticed that each island he visited had a different type of bird. To Darwin, it appeared that the islands were inhabited by many widely-varying species of birds (Wikipedia, n.d.). Upon his return to England, Darwin carefully analyzed his specimens. A bird specialist at the Natural History Museum, John Gould, told Darwin that all of them were finches. This led Darwin to speculate that all of the species arose from a few, or perhaps only one, bird who had arrived at one of the islands at some time in the past (Nebraska Citizens For Science, 2005).

Darwin’s Finches are about the size of a sparrow and similar in appearance except for their beaks, which are specialized according to how they are used. The size and shape of the various beaks indicate the diet of the bird. About 13 species of finch inhabit the Galapagos Islands (Galapagos Online, 1999). The Galapagos Giant Tortoise also shows how differences can arise when a species develops in isolation. There are 13 subspecies of the species Geochelone nigra found on the Galapagos Islands (Wikipedia, n.d.). Three additional species were probably hunted into extinction (Galapagos Conservation Trust, 2008). These large slow-moving reptiles were extremely abundant prior to the arrival of humans with perhaps as many as 250,000 by the time the islands were discovered (Wikipedia, n.d.). In the 1600’s buccaneers arrived on the islands and began to collect the tortoises and store them on their ships. They could easily be kept alive for many months and served as a source of fresh meat. Later, in the 1800’s, whalers killed them for their oil. When settlers began to come to the islands to live, not only did they hunt the tortoises for their meat, but they also cleared away much of their habitat to make room for agriculture (Galapagos Conservation Trust, 2008). The Galapagos Tortoise is a herbivore who eats many types of native vegetation found on the islands (Wikipedia, n.d.).

Approximately 560 plant species are native to the Galapagos Islands. Almost one-third of these are not found any where else, including species of cotton, pepper, guava, passion flower, tomato, and lava cactus. A favorite of the Giant Tortoise is Opuntia, the prickly pear cactus. Scalensia, the daisy tree, is a preferred perching site for Darwin’s Finches (Galapagos Conservation Trust, 2008). In addition to the animal and plant life on the islands of Galapagos, there are many life forms found in the ocean around the islands. Several ocean currents converge near the islands bringing an abundance of nutrients to the area. The cold Humboldt Current from the South brings cold Antarctic waters full of nutrients to the Galapagos (Wikipedia, n.d.). In fact, there is even a species of penguin which is able to survive there. The Galapagos Penguin is the only penguin species that lives in the Northern Hemisphere.

In 1793, James Colnett described the Galapagos Islands and encouraged whalers to come to the islands. They used the islands for a base, and they killed thousands of tortoises. The number of tortoises was reduced significantly. In fact, certain species are believed to have been totally wiped out. Also, there came fur seal hunters who brought them near extinction as well (Wikipedia). When settlers arrived on the islands, they also hunted some of the native species, and they destroyed the habitats of others; for example, the Giant Tortoise’s habitat was cleared away for growing plants the people wanted (Galapagos Conservation Trust, 2008).

Many species have been introduced to the islands by people. These introduced species reproduce rapidly and totally destroy the habitats of many of the islands’ natural inhabitants. Goats, pigs, dogs, cats, rats, mice, sheep, horses, donkeys, cows, poultry, ants, cockroaches, and parasites can all be found on the islands today. Wild goats were originally introduced to the islands by whalers and early settlers because they used them as a source of food. However, they destroy plants when they eat them. This leads to erosion and loss of vegetation (Nelson, 2007). In addition to goats, cows and donkeys eat much of the plant material that is available and trample much of what is left. Also, they compete with native species for what little freshwater is available (Galapagos Conservation Trust, 2008).

Cats and dogs attack birds and destroy their nests. They kill small tortoises and iguanas. In addition to eating native animal’s food, pigs also destroy nests of island reptiles and destroy other vegetation which could be used for food. The black rat attacks baby tortoises and has led to the disappearance of the native rat in areas where the black rat is found. The native species have no natural predators and have therefore not evolved any natural defenses to protect themselves. Introduced birds not only compete with the native birds, but they also pose a threat in that they might introduce disease into the native populations (Wikipedia, n.d).

Some of the introduced plants include the guava, avocado, blackberry, orange, grapefruit, and lemon (Wikipedia, n.d.). The guava, which is drought resistant, has replaced the natural variety and its shade blocks the sun from smaller plants (Galapagos Conservation Trust, 2008). In fact, in many areas the introduced plants have taken over so that native species are no longer found in these areas.

The marine areas around the islands are also threatened. One problem is the illegal fishing for species such as