photo courtesy World Wildlife Fund

Tortoises

The most recognized symbol of the Galapagos is the Tortoise. The islands common name is Spanish for saddle; referring to the shape of the Galapagos Tortoise Shell. With weights over 500 lbs (250 kg) and shells measuring 59 inches (150 cm) Galapagos Tortoises are among the largest on earth. These land-based turtles are slow moving and known for their long life span of more than 150 years.

The Tortoise played an important role in the Theory of Evolution. When Charles Darwin visited the Galapagos Islands, the vice-governor of the Islands told him that he could identify what island the tortoise was from simply by looking at him.

"The inhabitants...state that they can distinguish the tortoise from different islands; and that they differ not only in size, but in other characters. Captain Porter has described those from Charles and from the nearest island to it, namely Hood Island, as having their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island are rounder, blacker, and have a better taste when cooked."(Darwin 1845)

Galapagos Tortoise Geochelone Elephantopus
Naturalists believe Tortoises arrived in the islands clinging to a piece of driftwood from a river mouth along the Pacific Coast. A relatively large tortoise, related to the Galapagos Tortoise lives on the South American mainland. The tortoises arrived in San Cristobal then spread throughout the archipelago. Those on individual islands or in isolated parts of the larger islands developed into its own sub-species.

The Galapagos was once home to 15 sub-species of which 11 sub-species still exist. The smallest tortoises like those on Española and Pinta have "Saddle Backs', while the largest of the tortoises, those on Santa Cruz and from the Alcedo Volcano on Isabela have "Dome Backs". In this isolated habitat these giant tortoises fill the niche occupied by larger vegetarian mammals in continental regions.

They eat grass and cactus fruit, flowers and stems. Soon after the rainy season the tortoises descend the mountain slopes to feed on the grass covered flats. After that grass withers during the dry season they climb the mountain to feed on grasses of the moist meadows.

Tortoises and Man
When man arrived in the Galapagos Tortoises numbered in the hundreds of thousands. For millennia these animals had gone unhampered by predators. Ideally suited for rugged life in the Galapagos, tortoises are able to survive with little food and water during times of drought.

As the buccaneers, whalers and fisherman arrived in the islands they hunted tortoises as a source of meat. These same men brought pigs, goats, horses and cows whose existence in the islands threatened young tortoises. They ate the little vegetation that existed in the island and their hooves crushed tortoise eggs and the soft shells of young tortoises.

When the Galapagos National Park Service and Charles Darwin Research Station were established in 1969 all 11 remaining species of tortoises were endangered. One of their top priorities was stabilize the environment for the tortoises. This required eradicating the introduced species, encouragement of breeding and rearing of the young.

Tortoise Rearing Center
The Charles Darwin Research Station established a tortoise- rearing project. They have collected tortoise eggs from islands where the species has become endangered from the introduced species. The eggs are brought to the Darwin Station where they are incubated and hatched. The young tortoises are raised until their shells become strong and they can withstand the threat of the introduced predators.

This project, which began in the 1970's has been a success. Of the 11 species that were once endangered 10 species have been brought up to guarded levels. The most noted success story is that of the Española Tortoises. When the project began the Hood Tortoise population consisted of 2 males and 11 females. These tortoises were brought to the Darwin Station. Miraculously a third male was discovered at the San Diego Zoo and brought to the Darwin Station to join the others in a captive breeding program. These 13 tortoises are the parents of over 300 young tortoises now roam free on Española.

photo courtesy World Wildlife Fund

Iguanas

Iguana is the common name for a large "New World" lizard. "Iguana" a Spanish word of Indian origin also serves as the scientific name for the family. Iguanas are diurnal. They have distinctive eyelids, external eardrums, dewlaps (throat pouches), each limb has 5 toes with sharp claws allowing them to climb. Unlike most lizards, Iguanas are vegetarians.

The Galapagos Islands are home to Marine Iguanas, Land Iguanas and a Hybrid mix of the whose father's are Marine Iguanas and mother's are Land Iguanas.

Marine Iguana (Amblyrhynchus Cristatus)
Growing to approximately 3 ft (1 m) in length these sea-going Iguanas exist only in the Galapagos Islands. Living on the black lava shore rocks they have developed into efficient swimmers feeding off shore mostly on marine algae and seaweed.

The cold waters of the Galapagos provide both the necessary food for the Marine Iguanas and its most deadly threats. The cold temperatures can immobilize an iguana if it remains in the water too long. Until the arrival of man, Marine Iguanas only threats were that of larger fish and sharks encountered while swimming.

When Marine Iguanas are not feeding they seek safety and warmth of the land. In the 19th century when Charles Darwin visited the islands he found thousands of Marine Iguanas living along the rocky shore. He picked one up and threw it into the ocean it instantly swam back to the shore. This was repeated several times and the Iguana continued to seek the safety of the shore when it could have easily swum off to escape Darwin.

The black rocks under the equatorial sun provide needed warmth for the iguanas. On a warm day these rocks can heat up to deadly temperatures. Yet, territorial male Marine Iguanas, remain in the sun during the day. Cooled by a circulatory heat shunt carrying heat from the back to their bellies where the sea breezes coming off the cool ocean waters can cool them by convection. At night the iguanas pile by the hundred in order to provide heat for one another.

Galapagos Land Iguana (Conolophus Subcristatus)
Land Iguanas grow to a bulky girth and 3 ft (1 m) in length. Their yellowish-orange belly and brownish red back make them more colorful then their cousins the Marine Iguana. The Land Iguanas live in the arid portion of the islands.

The mainstay of its diet is the Prickly Pear Cactus. They eat the pads and fruit including the spines. The cactus provides both food and water for the Land Iguanas can go without fresh water for a year. Part of the adaptation to the drier environment includes a conservation of energy by slow movement. This makes the animals seem lazy or stupid. Land Iguanas burrow into the ground creating tunnels which provides a place for nesting, shade during the day and protection at night.