Trial release of the world's rarest tortoise Geochelone yniphora in Madagascar

A trial release of five juvenile ploughshare tortoises (Geochelone yniphora) was conducted in an area of natural habitat from which this Malagasy tortoise had apparently disappeared some 20 years previously. The trial release was a success. All five tortoises survived the first year in the wild. No homing phenomenon was observed. They established their home ranges near the release point, with no tendency to move in a particular direction. Maximum distance travelled was 746 m from the release point. However, captive-raised juveniles returned significantly less often to the same location over the time than did equivalent wild tortoises. There was also a significant difference in daily movement between the two groups, and captive-raised juveniles began aestivation more than one month after wild individuals. Released juveniles were able to resist a natural ectoparasite infestation. Their body mass changes mirrored those of the wild tortoises. Since the five captive-bred tortoises survived for one year, did not disperse, and appeared to have normal behaviour, release can probably be considered a viable conservation strategy for this critically endangered species. (C) 2000 Elsevier Science Ltd. All rights reserved.