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The natural regulation of Giant tortoise populations on Aldabra Atoll. Reproduction
Author(s) -
Swingland Ian R.,
Coe Malcolm
Publication year - 1978
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1978.tb03919.x
Subject(s) - biology , tortoise , reproduction , follicular atresia , population , population density , atoll , avian clutch size , zoology , follicular phase , sexual maturity , ecology , demography , ovarian follicle , endocrinology , sociology , reef
A two‐year reproduction study of three isolated populations of different densities of the Aldabra Giant tortoise ( Geochelone gigantea Schweigger) showed dissimilarity in gonadal parameters; (i) as population density increased age at sexual maturity was delayed in males and females; (ii) although the mean number of mature follicles was similar in all populations, preovulatory follicular atresia was only found in the high density population; (iii) annual variation in preovulatory follicular atresia was dependent on rainfall and food availability; (iv) the number of clutches laid/♀/year decreased with increasing population density as did clutch size; in the high density population (and depending on rainfall) only 30–80% of the mature females bred. The discussion considered the importance of movement in determining survival/reproduction.