So Aldabra tortoises exist in many zoos across the US. They are listed as Vulnerable by the IUCN and there are a very large number of them in Europe as well. However, in looking over the Chelonian TAG RCPs from both 2010 and 2016, there is no mention of Aldabra tortoises in captivity. In both RCPs, they only show up in the total list of chelonian species and nowhere else. I cannot find any information about an AZA program for this species and they are not mentioned in any other documents made by the Chelonian TAG. I found some articles about how the Tulsa Zoo is perhaps the only zoo that has bred them more than once. Here are two articles about that: Aldabra Tortoises Hatch at the Tulsa Zoo | Tulsa Zoo Tulsa Zoo winning race in Aldabra tortoise breeding programs So what exactly is the deal with Aldabra tortoises here? Is there a breeding program or not? Who is coordinating it? Where did all of the tortoises in North America come from?
Aldabra Tortoises are bred on Mauritius and Rodrigues (Indian Ocean) in their hundreds and some of these are exported internationally.
Very interesting questions. According to the National Zoo's website, there is a rare subspecies among the population and individuals are being DNA tested. Under the Physical Description category: https://nationalzoo.si.edu/animals/aldabra-tortoise That could potentially cause a halt in any breeding programs. As for origins: it's probably safe to assume that a decent amount are wild caught. I remember a post from the National Zoo's Facebook page that mentioned at least one of their individuals was, many years ago.
There have been suggestions that Aldabrans in captivity might actually be 3 species. However, when the genetics were done in the US - the same lab that did do all the Galapagos giants genetics work and continues to do so - it was found that they could not find any differences between "true" Aldabrans and other Seychelles tortoises. For now, it may have to be discounted. As Carl Jones will acknowledge, the giant tortoises are an important niche in the Indian Ocean island ecosystems and both Aldabrans and some Madagascan tortoises - the radiated tortoise - have been introduced to some Indian Ocean islands to re-establish that lost niche species and provide the ecosystem with an important germination / pollinator agent for various native and often endangered / threatened types of flora. I am not sure on the current workings of the AZA on Seychelles or Aldabran tortoises, but the European population is now working more towards making provisions to at least enable some breeding to occur in the near future. BTW: The work of the Tulsa Zoo in breeding Aldabrans is something quite out of the ordinary in US / AZA zoos for sure.
Aldabra Giant Tortoises show no currently recognised sub-species. The claim that there may be additional taxa, and that some of the extinct Seychelles Tortoises may still be present is not supported by DNA studies. There is considerable variation within the population and some of these these may be morpho-types. Aldabra Tortoises have been introduced to the islands of Ile aux Aigrettes and Round Island off Mauritius where they are breeding, and in part are fullfilling the role of the extinct Mauritian species.
I know there seem to be several facilities in Seychelles with large captive groups of Aldabra tortoise (Aldabrachelys gigantea). Are they breeding at those facilities or is it just exhibition?
So how long have these populations or morpho-types been separated from each other, in other words, when did these populations radiate?
It is even possible that an individual tortoise can grow a different shell shape depending from its neck movements during life. An interesting report was from one Asian zoo (Taipei?) which bred Aldabra tortoises after it changed their paddock from flat to uneven and fed them mostly branches suspended overhead. They found that tortoises on Aldabra live on very uneven ground and must eat branches most of the time. By changing the exhibit they achieved better fitness and success in mating and hatching. Giant tortoises, both Aldabra and Galapagos, are among the last species which do not commonly breed in Western zoos. I hope it will change soon!
These tortoises are all from a breeding centre on Rodrigues (Mauritius) where they breed hundreds annually.
Does this breeding center ever participate in re-wilding or is supplying zoological facilities all they do? Is that facility where you directly sourced tortoises for the restoration of Round Island or were the tortoises for that project sourced from elsewhere?
The centre on Rodrigues has its own rewilding projects, and its owners have supplied some tortoises for rewilding on Round Island.
There’s a significant amount in the private/pet trade in the United States, They are bred there. They are easier to move around than Galapagos tortoises due to their conservation status so they are more common.
I am also curious if the majority of Aldabra tortoises in captivity come from one single facility, how much genetic variation is there within the captive Aldabra tortoise population. Is inbreeding or genetic bottlenecking a potential issue, or was the founder stock of the tortoise population at that facility too large for that to be an issue?
It is curious how giant tortoises breed in the tropics in very basic paddocks, but in northern zoos very, very rarely they lay eggs. Something with the temperature? Low calorie diet? Granted, heating lamps in a zoo poorly mimic the actual temperature, and animal houses in zoos are good 10 degrees colder than the tropical temperature for tortoises.
