Linked to the previous image, Gentle Giant, which calls attention to the foraging habitat of the Galapagos giant tortoise, this one calls attention to the wastes of those animals, which constitute a limited and diminishing natural resource for numerous island organisms. The endemic giant tortoises of Galapagos (Chelonoidis spp.) 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 that 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.
The loss of 100,000-200,000 tortoises for their meat or oil in the 1800’s and 1900’s led to the extinction of 3 of the original 14 forms, verifying a clear lack of resilience to harvesting. Today the status of the 11 known surviving forms shows some improvement and the 20,000 remaining individuals have a status ranging from extinct in the wild to vulnerable. That Galapagos biodiversity loses when these large herbivores disappear is yet another reason to increase the incentive for effective local management.
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