Where do giant tortoises live?
Today, giant tortoises are found on a limited number of tropical islands, notably the Galápagos Islands, Aldabra Atoll in the Seychelles, and Mauritius. Some weigh up to 300kg and can grow to be 1.3m long. Though superficially similar, the Pacific and Indian Ocean populations aren’t closely related – but why did they grow so large?
Why are giant tortoises so big
The most established theory invokes the principle of ‘island gigantism’. If an animal becomes isolated from a crowded, species-rich ecosystem, it is freed from the usual environmental limitations caused by predation or competition for food or habitat that cap its size. The planet’s remote islands are peppered with examples of animals, both living and extinct, that fit this theory: the kakapo, New Caledonian giant day gecko, elephant birds, moas and Flores giant rat.
In the case of giant tortoises, the absence of competing mammalian herbivores, intra-specific competition for food and the ability to store energy in response to fluctuating food supplies all might result in an increase in body size. Moreover, as a cold-blooded reptile, its metabolism and overall ‘running costs’ are very low.
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