Mario Herz Figs. 10.
Mario Herz Figs. 10. View of the natural habitat of the Seychelles Giant Tortoise. lengths of much more than 100 cm would use their sheer body weight to incapacitate the significantly smaller females and so enforce mating. Copulation would usually take more than 20 minutes. While Pawlowski (2008) reported the husbandry conditions in human care to be largely poor in the Seychelles, I actually also became aware of encouraging approaches that were more in agreement with the European understanding of species conservation and animal welfare. In these instances, the owners were clearly motivated to keep their tortoises in good physical condition, even if only to maintain them as a public attraction in the grounds of hotel complexes. It was also in these places that I noted their being successfully propagated. The absence of wallows and suitable water holes that was criticized by Pawlowski (2008) was something I could not confirm. Another journey then took me to the Tanzanian island of Changuu off Zanzibar where a breeding colony of Seychelles Giant Tortoises is kept in naturalistic conditions and successfully propagated. While the environmental conditions are similar to those on the Seychelles, the natural food supply is deficient and necessitates that food be provided. The giant tortoises kept there were very active around 10.00 h, with several males being busy Fig. 11. Hatchlings of Aldabrachelys gigantea hololissa (Seychelles Giant Tortoise). 8 RADIATA 22 (4), 2013
Aldabra Giant Tortoise, Aldabrachelys gigantea gigantea Fig. 12. Mating Seychelles Giant Tortoises on Changuu Island; note the difference in size! The mating sounds of the male can be heard from afar. Fig. 13. View into the incubator at the breeding station on Silhouette Island (Seychelles); some baby tortoises have already hatched. Fig. 14. Hatchlings of Aldabrachelys gigantea hololissa (Seychelles Giant Tortoise). mating with females and many specimens congregating at the feeding spot. The entire “flock” appeared to be “on the move”. This might have been due to the fact, however, that it had stopped raining shortly before my arrival on the island. In the wild, mating takes place during the rainy season, i.e., from November through April. Oviposition then follows during the dry season between May and August. Clutch sizes vary from five to twenty eggs. Hatchlings will then emerge around the beginning of the next rainy season, about from October through December. The juveniles will remain in their nests until they have fully resorbed their yolk sacs into the plastron and the navel has grown closed and only thereafter start digging themselves to the surface. Freshly hatched, they measure about 60–70 mm in size and weigh ca. 50–60 g. Their shell will still be relatively low at this stage. By the time they are four years old, they will have grown to about 46–56 cm in length. They become sexually mature at an age of approximately 18–24 years (e.g., Ebersbach 2001). The juveniles hatching on Changuu Island are collected by the rangers stationed there and raised separately until they will have grown to around 50 cm in length. It was in December of 2006 that a dream of many years became true for me when I managed to acquire two Seychelles Giant Tortoises (Aldabra Giant Tortoises, Aldabrachelys gigantea gigantea). At the time, the two specimens weighed 150 and 155 g at carapace lengths of 9.4 and 10 cm, respectively. Their shells were still slightly elastic. A routine health check by a veterinarian revealed that their faeces contained parasitic worms. The juveniles were very shy in the beginning, which was an attitude I knew from juvenile Spurred Tortoises (Geochelone sulcata; Herz 2010) and found confirmed by Ebersbach (2001). Later, once they had grown to a more substantial size, the tortoises would lose this shyness and come running to their keeper the moment he entered the scene. The two baby giant tortoises were initially housed in a terrarium measuring 100 × 50 × 50 cm (length × width × height) and kept on RADIATA 22 (4), 2013 9
