A Naturalist's Pilgrimage to the Galapagos
Smithsonian's Laura Helmuth vacationed in the Galapagos Islands and returned with even more respect for Charles Darwin
- By Laura Helmuth
- Smithsonian.com, January 30, 2009
In drier areas, tortoises evolved to eat whatever was around, including prickly pear cactus. Notice how these are pretty tree-like? That's due in part to an evolutionary arms race between tortoises and cactus. Tortoises living where prickly pear was the main vegetation evolved longer necks and a shell that had a taller opening in front to allow the neck to stretch upwards. Tortoises with longer necks could reach more prickly pear cactus pads. And prickly pear cactus that grew taller and built a bark-like protective cover on their trunks were better able to avoid being eaten by tortoises.