Reproductive effort and life history strategy of the Aldabran giant tortoise


THE Aldabra giant tortoise, Geochelone gigantea Schweigger, has a large body size (19–120 kg)1, long life span (65–90 yr)2, late maturity (females 17–23 yr)3,4 and iteroparity3. The three isolated island populations of different densities on Aldabra show dissimilarity in their reproductive parameters (for example mean clutch size, mean egg weight, proportion of mature females breeding and the number of clutches per female per year) and in the variation of these parameters from year to year through annual changes in rainfall3. Moreover, their reproductive response to these changes in rainfall is rapid; they have a relatively high maximum (potential) rate of natural increase (maximum clutch size 28)3 and mature females in the high density population are half the weight of those in the low density area2,4. I have postulated that the reproductive effort would differ between the different density populations and that this effort would change in relation to changes in food availability. This contention is supported by the results reported here.

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SWINGLAND, I. Reproductive effort and life history strategy of the Aldabran giant tortoise. Nature 269, 402–404 (1977).

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