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Emergence Success of Tortoise Nests and the Effect of Feral Burros on Nest Success on Volcan Alcedo, Galapagos
Lynn E. Fowler de Neira and John H. Roe
Vol. 1984, No. 3 (Aug. 1, 1984), pp. 702-707
Stable URL: http://www.jstor.org/stable/1445152
Page Count: 6
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Volcan Alcedo on Isabela Island has a giant tortoise population of 3,000-5,000 and a feral burro population of 500-700 animals. To investigate the possible impact of burros on nest success, we monitored tortoise nests. The natural emergence success of Geochelone elephantopus vandenburghi during the 1979/80 nesting season was approximately 65%. Clutch sizes averaged between 11 and 14.5 eggs per nest, incubation periods varied from 90 to 150 days, and 75% of all nests contained one or more undeveloped eggs. Feral burros frequented the two main tortoise nesting zones and caused damage to incubating eggs by trampling. Of the 28 nests studied on the south caldera floor, 32.1% were broken into by burros. In the north caldera floor nesting area, 60 nests were monitored; 11.7% were disturbed by burros.