Mario Herz First
Mario Herz First Experiences with the Raising and Keeping of the Aldabra Giant Tortoise, Aldabrachelys gigantea gigantea (Schweigger, 1812) With their high value as show animals, giant tortoises have long been on public display in zoological institutions. One such example is the captive keeping of Seychelles giant tortoises in the Berlin Zoo dating back to 1845 (Junghans 1916, Petzold 1984). Encounters with these tortoises in zoos and animal parks have been key events in the lives of many terrarium keepers. Faced with these “giants”, many discovered their interest in animals in general and tortoises in particular. As far as the private keeping of animals is concerned, giant tortoises did not play a major role so far. The reasons for this being so are manifold. If at all, these tortoises were obtainable only with great difficulty, and their need for very large spaces was not easily fulfilled. Those who aspired to keeping a large tortoise in the past 30 years usually resorted to the African Spurred Tortoise (Geochelone sulcata), which has been propagated in large numbers. Increased imports of captive-bred Seychelles Giant Tortoises over the past years have made these more readily available, in spite of high prices. Specimens are typically offered at weights of 80–200 g and an age of 4–13 months. The correct name should actually be Aldabra Giant Tortoise, Aldabrachelys gigantea gigantea (Schweigger, 1812), but considering that the Aldabra Atoll forms part of the political territory of the Seychelles, applying the name “Seychelles Giant Tortoise” is not completely wrong. The “true” giant tortoises of the Seychelles are two forms that have been rediscovered only recently: Aldabrachelys gigantea hololissa (Seychelles Giant Tortoise) and Aldabrachelys gigantea arnoldi (Arnold’s Giant Tortoise) (Gerlach 2003, 2004a, b, Turtle Taxonomy Working Group 2012). Based on the markers used for their genetic studies, Palkovacs et al. (2003) and Austin et al. (2003) consider the differences (genetic differentiation) between these subspecies to be only minor. Fig. 1. The size difference between a giant tortoise of a few days of age and its presumed mother. 4 RADIATA 22 (4), 2013
Aldabra Giant Tortoise, Aldabrachelys gigantea gigantea Keeping these impressive animals in captive surroundings necessitates having an idea of their natural habitats. I therefore used visits to various islands of the Seychelles for studying the habitats of the tortoises living there. Being situated near the equator, the climate of the Seychelles is tropical and fairly unvarying. Temperatures oscillate between 24 and 30 °C, and the annual amounts of precipitation between 2,880 and 3,550 mm. The average minimum temperature is 24 °C, and being islands in the sea, the level of relative humidity is always high. All these aspects need to be taken into consideration when keeping animals from there in a captive setting elsewhere. The realizations from my field observations, even if limited to a few weeks, are complemented by information that can be deduced from Tingay (1998) and Jöchler (2008): - rains are irregular; - it is very hot and very humid (proximity to the coast), - the ground is highly calcareous; - the tortoises are active in the early morning and early even hours; - the population density is controlled by the availability of food and the weather (the animals need to protect themselves from overheating) - the availability of water and food controls reproduction; - they also feed on carrion, e.g., dead fish washing up on the beaches. I had opportunity to observe free-ranging tortoises on the uninhabited Seychelles islands of Cousin and Curieuse that have sandy beaches in places. On Cousin Island, these are used as oviposition sites by the Hawksbill Turtle (Eretmochelys imbricata) and the Green Sea Turtle (Chelonia mydas). This island is designated as a bird sanctuary and offers refuge and opportunity to nest to a multitude of birds. All tortoises living on Curieuse and Cousin today originate from Aldabra and were at one stage released here to form a “reserve population” that could be accessed if the original population became extinct (Hambler 1994, cit. fide Pawlowski 2009). Fig. 2. View of the by-now closed-down installation of the NPTS (the tortoise and freshwater turtles breeding station on Silhouette Island, Seychelles). Fig. 3. A typical tortoise pen Seychellean style – these enclosures are most commonly found in hotel grounds. Fig. 4. A pen for keeping Arnold’s Giant Tortoises (Aldabrachelys gigantea arnoldi); visible here are a male and two females. RADIATA 22 (4), 2013 5
