The Giant Tortoise (Geochelone elephantopus, syn: G. nigra) is the Galapagos Islands
icon. The islands are named after them — the Spanish for the giant tortoise is "galapego" which comes
from their word for saddle after the saddle-shape of the shell. (Note: the shell is correctly called the
"carapace.") If you look at early maps, you will see
the name "Ins. de Galapegos" (Note: Ins. stands for Insulae, which is Latin for "island.") These are
the world's biggest land tortoises. A full grown adult weighs well over 500 pounds and measures five or six feet
long and three feet high. They are believed to be very long-lived, perhaps exceeding the human life-span, although
there are no confirmed records.
The tortoise eats a wide range of plants and scientists have recorded over 50 different species in its menu. It loves
Manzanillo fruits, or poison apple (Hippomane mancinella) only a few of which of which can kill a person. It
also likes to eat fallen prickly pear cactus pads (Opuntia). They can survive for long periods without water,
but when they have the chance drink copious amounts of water. Darwin observed them drinking "quite regardless of
any spectator" as they sink their head under the water and "greedily swallow great mouthfuls, at the rate of
about ten in a minute."
The thought of these cumbersome lumbering animals procreating invariably raises giggles among tourists listening to
their guide at the Charles Darwin Research Station. Yet that's how the tortoises perpetuate themselves. Breeding
season is in the cooler time of year beginning May or June, during the wetter period so females are in better
condition to make eggs and the effort to lay them. Females are smaller than males and sometimes seem reluctant to
accept an eager suitor. But to no avail, as the huge male uses his weight to pin down the female until mating is
over. The tortoises take at least 20 years to reach sexual maturity, so their populations are slow to recover losses.
The female excavates a pit using her hind legs and deposits up to 15 eggs each about the size of a baseball. She then
covers the nest up and there the eggs incubate for four to five months. Upon hatching the tiny tortoises must dig
their way out and thereafter fend for themselves. A lot of young are lost at this stage, although hawks are the only
native predators.
The history of the tortoise is not a happy tale. Early visitors such as pirates and whalers saw the tortoise as a
walking food source, a notion reinforced by the fact that a tortoise can live for up to a year without any food or
drink. Hence tens of thousands of the animals were removed to sailing ships as a source of fresh meat on long sea
voyages. Estimates put the loss at 200,000 tortoises during the 18th and 19th centuries (see History Timeline). Originally there were thirteen sub-species,
now only ten remain. Islands on which they are extinct are Floreana, Fernandina and Santa Fé. Scientists think that
depredations by imported animals such as rats (which eat the eggs and hatchlings), cats and dogs helped finish off
the decimated populations. The present population is put around 15,000, mostly on Isabela.
But Darwin was impressed. He was struck by the islands' vice-governor's remark that he could tell by the
shape of the shell which island a tortoise came. Indeed, this is the main way the different races of tortoises
differ, and influenced Darwin's line of thought that led him to his theory of evolution. The different shape
shells are related to the tortoises niche. Tortoises that live on dry islands such as Hood have carapaces raised at
the front so they can reach up for vegetation. Tortoises on large islands with dense vegetation have domed carapaces
that help them push through the shrubbery.
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