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The isolated volcanic islets of the Galapagos archipelago, some 200 miles from the coast of Ecuador, are inhabited by a group of giant tortoises that were made famous during Darwin’s exploration- of these islands. Specimens with shells 5 feet long and almost 3 feet in height were once common, and these weighed well over 450 pounds.
It is remarkable that the tortoises of islands only 30 miles apart show such different and characteristic shell shapes that local hunters could identify the islands from which they had been collected. This immediately raised questions regarding the origin of such variation. Populations now on islands where vegetation grows higher seem to be saddle-backed: the shell is bent upward at the neck so that they can browse. The grass-eaters have a more characteristic domed shell.
These tortoises are coadapted to the other life on these islands, for the seeds of some local plants will germinate much more readily if they have first passed through the gut of a giant tortoise.