The body wastes of Galapagos giant tortoises constitute a limited and diminishing natural resource for numerous island organisms. The endemic giant tortoises of Galapagos are the only native terrestrial herbivores that move throughout the islands. By leaving their droppings behind, they transport quantities of semi-digested biomass from the highlands to the lowlands. They open gaps in the forests, and undigested seeds of certain plants they consumed germinate at a higher rate than those that were not consumed: The droppings attract insects, which become a food source for insectivorous warblers, finches, mockingbirds and Lava Lizards (Tropidurus spp.). The visited droppings decompose quickly, generating soil and fostering the growth of germinating seeds. As producers of this resource, tortoises are a keystone species of Galapagos. Wherever they disappear, island biodiversity loses.
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