Animal of the Issue: Galapagos Tortoise

The Galapagos Islands, which were discovered by Spanish sailors, were named after the giant tortoises discovered there. “Galápago” means tortoise in Spanish. Photo Credit / Dr. Terry Master
The Galapagos Islands, which were discovered by Spanish sailors, were named after the giant tortoises discovered there. “Galápago” means tortoise in Spanish. Photo Credit / Dr. Terry Master

The Galapagos Islands, which were discovered by Spanish sailors, were named
after the giant tortoises discovered there. “Galápago” means tortoise in Spanish.
Photo Credit / Dr. Terry Master

By Briana Magistro
SC Staff Writer

Have you ever heard of the famous biologist and explorer Charles Darwin, who traveled on the British exploration vessel “The Beagle?” I am sure you have! Most famous for documenting finches and other species in the Galapagos Islands, he obtained information that later lead him to develop the concepts of evolution and natural selection.

The Galapagos Islands lie off the western coast of Ecuador and were only settled by humans in the 1800s. These islands host a mainly arid-tropical climate, but some are volcanic and display a greener environment at the highest points on the island. Due to these climate variations, each island may provide unique sets of plants, resulting in unique collections of species, such as the Galapagos tortoise.

These tortoises, just like turtles, reside in the biological order Testudines.

“Turtles form a very distinctive group of reptiles that can be characterized by the universal presence of a shell that is composed partly from bone and partly from epidermal scutes,” stated Dr. LaDuke, East Stroudsburg University’s herpetologist.

However, what sets tortoises apart from turtles are their elephant-like legs and feet. “The leg is cylindrical and generally held more-or-less strait, while the foot itself is very short,” continued Dr. LaDuke. Most tortoises also have domeshaped shells, while turtle shells are flatter.

When it comes to habitat, many tortoises live in semi-arid or subtropical climates, and they feed on vegetation.

Wild Galapagos tortoises, in particular, can only be found on the Galapagos Islands. Due to the nature of the separation of the islands, the tortoises can be further classified into races. This division parallels to how dogs are grouped into breeds.

Each race resides on one island and cannot breed with any other races. These races all have specific characteristics, which aids in classification.

Although each race displays its own characteristics, all Galapagos tortoises are alike in that they are herbivorous, adapting to the diet provided by its island.

“The tortoises of the Galapagos Islands are true giants of the reptile world,” shared Dr. LaDuke. These creatures can grow up to 6 feet long and weigh up to 500 pounds!

In addition to their large size, these tortoises are believed to have a lifespan up to 200 years, but no real documentation exists that proves they can really live that long.

Dr. LaDuke commented, “Because tortoises are long-lived, it is rare to find a well documented case in which a continuous record of an individual’s existence has been maintained throughout its life. One of the main problems here is that zoo-keepers do not live as long as the tortoises, and, in the past, there was often a break in recordkeeping when one zookeeper dies and another takes over.”

In support of the longevity of these tortoises, some argue that Darwin himself documented Harriet, a Galapagos tortoise currently living in an Australian zoo. Some scientists, however, are more skeptical about Harriet’s age.

“If true,” commented Dr. LaDuke, “Harriet celebrated her 175th birthday in 2005.”

Another famous tortoise, Lonesome George, was the last of his race to be discovered on his home of Pinta Island in the Galapagos. Previous evidence showed that his race had been extinct for many years. Since his discovery, surveys of the island have not shown any other tortoises like him. George passed away in 2012 at an estimated age of 80 to 100 years old.

Because they grow large in a short amount of time, Galapagos tortoises do not have many natural predators. By the age of one, the tortoises are too big for hawks and other birds to prey upon.

The tortoise’s main threats reside in the dogs, rats, and goats brought to the islands by colonists. These animals dig up tortoise eggs and eat the tortoise’s vegetation.

These tortoises typically lay 4 to 10 eggs in groups called clutches. Tortoises do not mate for life, and a male will mate with as many females as possible during the breeding season.

During the age of exploration, many ships gathered these large animals and utilized them as a food source. As a result, thousands of tortoises were taken from the island, and today they are considered endangered.

“The tortoises were particularly valued because they could survive for months below decks without any food or water,” said Dr. LaDuke.

The generally docile nature of these tortoises may have been a factor in their easy capture. Humans can usually get very close without upsetting them.

Today, conservation efforts are being made on the islands themselves to try and save the Galapagos tortoises. Tortoise eggs are hatched in captivity, and babies are released to their respective islands when they are five years old.

“Without this breeding program,” said Dr. LaDuke, “most of the races of tortoises would probably have gone extinct in the wild already.”

Email Briana at:
bmagistro@live.esu.edu

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