Giant Tortoises Saving Island Ecosystem

On Ile aux Aigrettes, an island off of the coast of Mauritius, scientists introduced the Aldabra giant tortoises to try and revive the island’s dying ecosystem. 

Before humans reached the Ile aux Aigrettes, the island was full of tortoises, skinks, and dodo birds.  The disappearance of these animals devastated the ecosystem, especially the native ebony trees that were already being cut up for firewood. 

The giant tortoises, who can reach up to 661 pounds, were introduced to try and spread the seeds of the dying trees that still remain on the island. The tortoises eat the fruit from these trees, spreading them around the island.  Without these animals, the seeds from these trees could not disperse, and young trees would only grow right under the older trees.

Usually, an invasive species is viewed as a threat to biodiversity.  The idea of replacing an extinct animal with an alien one is controversial, but it has been done elsewhere with species that are closely related to the ones they are replacing.  For example, the North American peregrine falcon was re-established by species from different continents, and herons were introduced to Bermuda to replace extinct ones to manage the population of land crabs.

However, the addition of the Aldabra giant tortoises to the island was not as complicated because of the lack of predators, meaning that the food chain is simpler. 

So far, new patches of seedlings have begun to grow where the tortoises most commonly occupy, and the tortoises have been eating the non-native vegetation.  Whether these seedlings will grow into trees that reproduce remains to be seen, but the tortoise experiment seems to be working thus far.    

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