Research Items

Abstract

Age of the Giant Tortoises of Galapagos.—In 1928 a number of giant tortoises, all belonging to the species Testudo vicina, were brought from the Galapagos Islands by the New York Zoological Society and deposited at different stations where their development might be watched. At the stations the rate of growth differed, the three individuals in Arizona showing only a 66 per cent increase, while in Florida and Texas more than 200 per cent increases were attained (C. H. Townsend, Zoologica, vol. 9, p. 459 June 1931). The author states that the differences are traceable chiefly to climate and treatment, but it is obvious that size is also an important factor, smaller specimens on the whole showing the larger growth percentage. The age of the giant tortoises while comparatively young seems to be traceable in the striations of the horny plates of the carapace. Where age is definitely known up to twelve or even twenty years, the striations agree in number with the years, but in larger and older individuals the ridges tend to flatten out and become illegible. The author states that the common notion that large Galapagos tortoises must be of extremely old age is unwarranted, though he adds that the real length of life is unknown. Under favourable conditions they reach a large size in a few years, when the rate of growth becomes slow. Nevertheless, there are records of giant tortoises from both Galapagos and Aldabra which lived under observation in tropical climates for more than 150 years, dying upon their removal to cold climates.