I correspond with a bloke in Europe who has done a thesis on breeding giant tortoises. A lot of his research was done on privately owned animals but some zoo stock was involved.
He has found that giant totoises are a bit like elephants - if the females don't breed when young, then they are unlikely to breed at all.
There is a lot more work to be done with breeding giant tortoises, of course, and he doesnt claim to have all the answers yet.
However, if he is right, then the years that Australia wasted by insisting on DNA classifying all our Galapagos by sub species, may mean that we will never breed Galapagos here with our existing stock.
Exactly what are the ages of the Galapagos at TWPZ and what sub species are they said to be??
It would be interesting to learn more re those studies, age at first breeding and perhaps even choice of partner.
I am however of the opinion that all Galapagos should be maintained according to natural species (these days more and more they are being raised to individual species level). Natural hybridisation zones do occur, but in the Galapagos giants one has domed and saddle-back species which have quite different behavioral and reproductive patterns.
Unless, all Galapagos tortoises are maintained in correct species settings and enclosure design, sufficient UV/sunlight, adequate feeding regimes AND separating occassionally the sexes (the males get over-indulgent otherwise and then impair natural breeding and egg-laying condition in the females) replicate their natural requirements NO giants will EVER breed.
True example of natural breeding in correct species setting is Brownsville Zoo in Texas, USA. It has been a hard and difficult road in coming and setting up pairings, but now these breed to production line. And these are not exactly youngish ...., with recently a newly set-up pair breeding for the first time. Reptile maintenance and breeding is often a labour of love for the curator and staff, their talents in this ultimately decide success or failure.
Several zoos have bred in the past including those at Chicago and Phoenix.
In Europe not sufficient wild caught specimens have been going around and only Zuerich Zoo breeds to excess. Alas, here, from individuals known to be different species (becki and porteri). The sad thing here is that sufficient individuals of becki and porteri can be found to set up correct mating pairs and really get down to the business.
The very fact that few zoos feel any serious interest towards attempting to breed their giants using the latest knowledge and technology in giant tortoise breeding pen design - as private individuals have done - all PRECLUDE the breeding.
K.B.
POST SCRIPTUM: You are welcome to pm us as I have tonnes of info on giants (both Seychelles, Aldabrans and Galapagos as well as those long extinct of the Indian Ocean basin).
but after learning Bona's name today am pretty sure it was Bona's fur and not Chester's that i use to have. Apparently Bona died in 2002 