Reproduction

KUBISCH, E.; IBARGÜENGOYTÍA, NORA RUTH

Galapagos Giant tortoises

Elsevier

Año: 2021;

The life history strategy of turtles and tortoises is characterized by delayed sexual maturity, extended longevity, and repeated reproductive events (iteroparity), with high and variable rates of mortality of embryos and hatchlings and low reproductive success per reproductive event.Galapagos giant tortoises take this strategy to an extreme. Sexual maturity is delayed for up to two decades or more and longevity after surviving the juvenile stage can extend to well over a century. Once they reach sexual maturity, Galapagos giant tortoises generally reproduce annually for the rest of their lives. Their annual reproductive cycle follows, as in all turtles, a sequence of events, including production of gametes (ovule or sperm), mating, and nesting, which includes nest site selection and oviposition, incubation, embryo development, and hatching. Surviving off-spring are recruited into the larger population, eventually becoming reproductive adults approximately two decades later (Chapter 12: Population Biology). Understanding thereproductive cycle of Galapagos tortoises is vital for their conservation because captive breeding followed by reintroduction and nest protection in the wild are key strategies for increasing populations of threatened species (Chapter 17: History of Conservation). The reproductive biology of Galapagos tortoises has not yet been intensively studied. Observation of the tortoises in their natural habitat is challenging due to remoteness and difficulty of access to their nesting zones,extended breeding seasons, and low densities of tortoises across large areas. In addition, the protected status of these species restricts the use of invasive methodologies helpful for studies of gametogenesis and fecundity. Consequently, most observations of tortoise reproductive biology are based on individuals in captive situations with more limited observations from the wild.