22 - Slow and Steady Wins the Race: Using Non-native Tortoises to Rewild Islands off Mauritius

Summary

The radiated tortoise and Aldabra giant tortoise were used as ecological replacements for the extinct Mauritian tortoise Cylindraspis inepta. Aldabra giant tortoises were better adapted as seed dispersers and grazers, and have become the species of choice. It is intended to remove the radiated tortoises from Round Island. It is suggested there was an open grazing climax plant community maintained by tortoises with heliophilous native plants that have adaptations to avoid being grazed or browsed and respond to grazing with prostrate growth form. The Aldabra giant tortoises fed on fallen fruits and spread the seeds of hardwood trees, screw-pines and palms in their droppings that subsequently demonstrated enhanced germination and growth rates. Preliminary work was done on Ile aux Aigrettes before the release on Round Island. The tortoises have established grazed areas colonised by the native tussock grass Chrysopogon argutus that the tortoises do not graze and is benefiting from reduced competition from the fast-growing non-native grasses.