Predation on the angulate tortoise Chersina angulata by the kelp gull Larus dominicanus on Dassen Island, Western Cape

Abstract

The kelp gull (Larus dominicanus) is an important predator on the angulate tortoise (Chersina angulata) on Dassen Island, Western Cape, South Africa. Tortoise shell fragments (n= 142) were collected and measured. Using regression curves based on 184 live tortoises measured on the island, the size class of tortoises eaten by kelp gulls was determined to include tortoises from 38-124 mm (mean 84 mm) total length (mass 25-350 g; mean 130 g). It is probable that very small tortoises were also eaten, but totally consumed. It is suggested that predation on tortoises occurs during the autumn-winter by the small population of resident gulls (approximately 50 individuals).