A COMPARISON OF TWO METHODS OF ESTIMATING THE SIZE OF A POPULATION OF GIANT TORTOISES ON ALDABRA.

From a sample census of giant tortoises in the south-eastern region of Aldabra atoll, the size of the markable population was estimated as 87 300. A subsequent recapture study of the same population gave an estimate of 68 100. Sampling errors are unlikely to account for the difference, which is significant at the 1% level. After taking into account obvious violations of the underlying assumptions the difference remains. The sample census estimate is thought to be the more reliable. [ABSTRACT FROM AUTHOR]