What are the Feeding Habits of Galapagos Island Tortoises?
Galapagos Island tortoises are giant land-dwelling turtles found only on the Galapagos Islands, an isolated Pacific archipelago 450 miles off the coast of Ecuador. Males can weigh as much as 550 pounds, with shells more than 5 feet long. The tortoises can live more than 150 years.
Charles Darwin's encounter in 1835 with the unusual creatures contributed to the formation of his theory of evolution by natural selection. Of the 15 subspecies that existed then, 11 survive.
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Feeding Habits in the Wild
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Galapagos tortoises are peaceful, slow-moving herbivores that occupy the ecological niche usually occupied by large grazing mammals like deer or antelope. The Galapagos Islands have no native mammals, which allowed the tortoises to evolve into the primary plant eater. Grasses and prickly pear cactus form the basis of their diet, which also includes flowers, leaves, lichens, ferns and fruits.
Diet in Captivity
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Galapagos tortoises are in residence at a number of zoos around the world. At the San Diego Zoo, tortoises eat kale, collard, mustard and dandelion greens, bok choy and a variety of other vegetables and fruits. The Philadelphia Zoo feeds theirs a commercial feed mix, apples, carrots, salt marsh hay, kale, salt and mineral powder.
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Diet and Adaptation
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The shell shape of the different subspecies is directly related to its environment and the available food plants. Dome-backed tortoises live in higher, moister areas and eat primarily grasses and low shrubs. Saddle-backed tortoises live in dryer regions and eat mostly taller plants. Their shells are arched in the front, allowing them to stretch their long necks higher to reach vegetation above their heads.
Tortoises as Food
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Until humans discovered the islands in the 16th century, Galapagos tortoises had no natural predators. The tortoises can survive for as long as a year without food or water. This extraordinary ability led 17th century pirates, whalers and merchant sailors to stow the creatures in their ships' cargo holds to serve as a living meat storage system. The practice declined in the mid-19th century.
Conservation Status
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Today the tortoises are considered an endangered species, despite captive breeding programs. Only a few wild populations exist and are threatened by human encroachment on their habitat, poaching and devastating predation of eggs and young by non-native mammals, especially rats, dogs and cats. In addition, they must now compete for food with free-ranging goats and cows. A single surviving representative of one of the subspecies, known as Lonesome George, is in residence at the Galapagos Island's Charles Darwin Research Station.
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