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LatestPhoto
Owen Griffiths standing with 'Domino' - a ninety year old, 290 kilogram Aldabran Giant Tortoise. He is one of the ten largest giant tortoises in the world.
Photo : Chris Johnson

November 30, 2003
'Bringing the Giant Tortoise Back to the Mascerenes'
Real Audio Report
  28k


Log Transcript

This is Genevieve Johnson speaking to you from Mauritius in the Indian Ocean.

Three distinct groups of giant tortoises existed at the beginning of the sixteenth century. As big as bears, these tortoises were confined to small oceanic islands.

It is remarkable to consider that during the first four years of the Voyage, the Odyssey crew visited all three oceanic island regions that once supported enormous unwieldy herds of giant tortoises. Two of these regions - the Galapagos and the Seychelles, still support fragments of the original populations, while the third region, the Mascerene Islands have lost all five of their endemic species - forever.

Today, the crew took a trip to the southern end of the island to meet an exceptional biologist by the name of Owen Griffiths. Owen owns and manages a nature reserve called La Vanille Reserve de Mascerene where he is currently breeding Aldabran giant tortoises.

Owen Griffiths:

    "Basically what we do is we breed crocodiles, Nile crocodiles introduced from Madagascar. We breed Aldabran tortoises and we are an eco-tourism center, we're a mini-zoo and an education center."
LatestPhoto
Mating behavior is often observed in the reserve.
Photo : Chris Johnson

Genevieve Johnson:

It is said that giant tortoise populations in the Mascerenes were the most abundant. Indeed, it is believed that Rodrigues had the largest population anywhere in the world. One traveler noted - "There are on this island such great abundance of these tortoises, that one sees them in troops of sometimes 2 or 3 thousand, such that one can take more than a hundred steps on their backs without touching the ground."

However, once humans discovered the Mascerenes, it didn't take long for the full process of extermination to begin. Settlers on Mauritius butchered tortoises by the thousands. Later, the world's navies and whaling fleets made a grim discovery that sealed the fate of the giants. The endurance of the reptiles under extreme conditions coupled with their slow metabolism meant the tortoises could be stored alive for months in the holds of ships without food or water. To prevent wandering, these hapless creatures were stored upside down until it was their turn to feed the crew.

By around 1780, the tortoises of Rodrigues, Mauritius and Reunion were exceptionally rare in the wild, most having been consumed by man. No one knows the fate of the last individual, but by 1836 when Charles Darwin visited Mauritius aboard the Beagle there was not a solitary tortoise to be found.

Owen is currently undertaking an ambitious program aimed at partially restoring the Mascerene ecosystem to its original state by releasing Aldabran giant tortoises into the wild on Rodrigues.

Owen Griffiths:

    "The purpose and the history, if you would like, when I came here, because I fell in love immediately with Giant tortoises. Whenever some came up for sale in Mauritius, I would acquire them and bring them here and got interested in the breeding. As we were more successful and produced in excess of 200 babies every year now - then the idea came to me and some colleagues, it would be really nice to have them back in the wild. For a number of reasons, that does not work on the island of Mauritius, but it would work very well on the island of Rodrigues. We have now applied to the government and we are going to lease 20 hectares of land in the limestone area of the southwest, replant 75,000 endemic plants to create the original palm savannah and have a 1,000 giant tortoises in the wild before the next decade."

Genevieve Johnson:

The Aldabra species is not as closely related to the five Mascerene species as the Mascerene species were to each other. In fact, the Aldabran giant tortoise is probably descended from a separate branch of the genus, originating from a long since extinct species from the north coast of Madagascar. However, it is believed the Aldabran's are similar enough to fill the ecological niche left by the extinction of the Mascerene giants.

LatestPhoto
Owen's captive breeding program produces over 200 hatchlings per year.
Photo : Chris Johnson

Owen Griffiths:

    "In Rodrigues now, we are re-creating ecosystems. All of the lowland forest is all gone. There are tiny remnants, which enable us to get seeds to re-create the forest - and then yes, you are quite right - the tortoises were a fundamental player in shaping those eco-systems. So they will be coming back as we re-create the lowland forest ecosystems."

    "The Mascarenes have a high proportion of heterophilic plants, which means they have different kinds of leaves according to the height that the leaves are growing - which is amazing. Low down, they have very pointed leaves with a lot of red coloration. Above a certain level, it just changes to a more normal, more conventional leaf and people believe that the shape and the color of the low-down leaves, help them avoid being browsed by tortoises. So they absolutely were a dominant force in shaping the evolution of plants in the Mascarenes. Also, they are seed distributors. So, on the Ile aux Aigrettes, underneath the Ebony trees, all the seeds just fall and spout under the mother tree and die - it's all shaded. Since they have brought tortoises back - the tortoises eat the ebony seeds and pass them out a hundred meters away and there are baby ebonies coming up everywhere because if that. So that immediately shows their role as seed dispersers."

Genevieve Johnson:

Aldabran giant tortoises are kept in several zoos around the world, but breeding the species is proving to be difficult. However, Owen is able to successfully breed these animals while artificially managing the sex ratio of the hatchlings within his captive population.

Owen Griffiths:

    "Well, a lot of people come here and they think that I am a very clever person and I have done some incredible thing to breed them so successfully. I look after the tortoises well, they have got plenty of space, they have got a good diet, a good diet in terms of what tortoises require, plenty of sunshine and they just do what comes naturally. Obviously, there is important management in terms of removing the eggs into the incubator - setting incubators at different temperatures so that you produce males and females."

    "If you incubate Aldabran tortoises at 30 degrees (celsius) and up - within the survival limits - they will all be females. If you drop sort of below 29 (degrees celsius) - again within survival limits - they will all be males.

Genevieve Johnson:

Mauritius has changed dramatically over the past 400 years, and today there are numerous challenges and threats involved at the breeding sight and when releasing these animals into the wild.

Owen Griffiths:

    "Well here in the park, the two challenges are - rat predation. You have got to make sure that your enclosures are rat proof. We have had one rat get in one night; he killed 5 baby tortoises in one clip. And, the other problem of course, unfortunately, is thieves and we have had one break in from very professional, European based reptile thieves who stole 161 babies in one night."
LatestPhoto
For the first few years of life, baby Giant tortoises are housed in a secure enclosure protecting them from predation and theft.
Photo : Chris Johnson

Genevieve Johnson:

The ecosystem of the Mascerene islands will never be what it once was - a menagerie of fearless and unique animals existing in a wild, lush forested landscape. To restore it to its former glory is impossible. However, the work of dedicated individuals like Owen Griffiths is a step in the right direction and the least that can be done in an attempt to make up for the past violations by man.

Owen Griffiths:

    "Oh, I always fantasize about being plummeted into pre-human Mauritius - it must have been great - fantastic forests, cool streams coming down to the coast, Dodos scratching around in the leaf litter, Giant Parrots scratching around in the leaf litter, lagoons absolutely teaming with fish, right beyond the edge of the water. It must have been fantastic!"

Links:

Written by Genevieve Johnson.

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