The atoll has distinctive fauna including the largest population of giant tortoises ("Aldabrachelys gigantea") in the world (100,000 animals). Tortoise size varies substantially across the atoll, but adult tortoises typically have a carapace length of about and can weigh up to . They are herbivores and feed on a variety of plants, trees and even algae that grows in the freshwater pools. The tortoises mate between February and May, the females then lay their eggs from June to September in areas with suitable soil layers. They lay eggs (the size of golf balls ) in a clutch of three to five eggs every few years in high-density areas and 14-16 eggs in low-density areas. The females can lay several clutches in a year and the incubation period is 73–160 days. The small vulnerable juveniles have to survive the predation by coconut crabs, land crabs, rats and birds. In the past giant tortoises have been relocated to many other islands in Seychelles and also to Victoria Botanical Gardens in Mahé. One of the longest-lived Aldabra giant tortoises was Adwaita, a male who died at the age of about 250 years at Kolkata's Alipore Zoological Gardens on March 24, 2006.