The Aldabra Atoll northwest of Madagascar, consisting of four large and many small islands, was able to preserve flora and fauna that were not influenced by humans due to its isolation. The islands are grouped around a lagoon and are enclosed by an outer coral reef. The natural paradise is the largest atoll in the Indian Ocean and is best known for its large population of giant tortoises.
Aldabra Atoll: Facts
| Official title: | Aldabra Atoll |
| Natural monument: | a 34 km long and at most 14.5 km wide atoll with a total area of 350 km², four larger coral islands (Grande Terre, Malabar, Picard and Polymnie), which are located around a 140 km² large lagoon and are surrounded by an outer coral reef; nature reserve since 1976 |
| Continent: | Africa |
| Country: | Seychelles, see findjobdescriptions |
| Location: | northwest of Madagascar and east of mainland East Africa |
| Appointment: | 1982 |
| Meaning: | Due to the isolation, flora and fauna unaffected by humans, the last habitat of the giant tortoises found in the Indian Ocean |
| Flora and fauna: | 178 species of plants, 97 species of birds |
Island of the giants
Giant tortoises used to trudge through the undergrowth on all the islands of the Indian Ocean before they fell victim to the meat needs of seafarers and settlers. They could only survive on the most inhospitable islands of the Aldabra Atoll. It is hard to imagine how they can find their way over bizarre coral blocks and find enough food on the barren coral islands. They feed on grasses and herbs, but also graze leaves from bushes and trees as far as they can reach them. They have developed an additional source of food for themselves by feeding on the carcasses of their conspecifics and thus ingesting high-quality protein and calcium.
The giant tortoises were very fortunate that the islands were off the shipping routes, that the surrounding waters were extremely dangerous and that there was a lack of drinking water and timber. Bulky mangrove forests and impenetrable thickets of aldabra screw trees and pemphis bushes, in combination with the razor-sharp, jagged coral bed, were such an effective protection against intruders that today Aldabra is the only pristine island in the Indian Ocean that has been able to preserve its unique flora and fauna.
The atoll consists of four main islands and a few small islets that surround a huge lagoon. Most of the surface consists of a coral reef that is thousands of years old and raised above sea level.
The tidal range is so enormous that the huge lagoon falls empty at low tide. The water flows in and out with great force through the narrow channels between the islands and washes the lower parts of large coral blocks so that they stand on pillars and form expansive tables.
Aldabra is home to even more giants! The world’s largest land invertebrate, the palm thief, is a land crab that measures up to a meter from tip to tip. In addition to bird eggs and chicks, he feeds on coconuts, which he can open with his incredibly powerful claws!
A small brown rail with a white throat is Aldabra’s most famous bird. The Cuvier’s railing is the last survivor of the many flightless species of railing that inhabited the islands in the Indian Ocean before they were wiped out by humans. The couple’s loud courtship song is astonishing as they perform a series of high-pitched squeak and squeaking tones alternately and with each other in a duet.
Lively groups of aldabra tapers scurry around in the thick bushes, and aldabra nectar birds search for flowers and insects. During the breeding season, the males adorn themselves with bright colors, orange-red the weavers, and the nectar birds glow in the sunlight like iridescent blue-green gemstones.
The black Aldabradrongos are only native here, other land birds such as Comoros fruit pigeons, Madagascar refugees and Madagascar spectacled birds immigrated from the nearby islands of the Comoros and Madagascar.
Undoubtedly the biggest attraction are the huge breeding colonies of sea birds. During courtship the males of the banded and ariel frigate birds offer an incomparable spectacle. They sit in the mangroves with bulging, bright red throat pouches and try to lure the females with conspicuous flapping of their wings, turning their heads back and forth and clicking sounds.
Frigate birds are the pirates of the tropics. They are the perfect flight artists. From motionless standing in the wind to a frenzied dive with sharp curves and twists and again lightning-fast carrying up, they show aerial acrobatics that no other bird can match.
This enables them to steal their prey from the other sea birds. Red-footed boobies and tropical birds that have fished far out in the open sea are attacked by the frigate birds with powerful beak blows until they choke out part of the goitre that the frigate birds still catch in the air.
The islands were known early on to the seafaring Arabs, who referred to them as “Al Khadra” – “the Greens”. They were already recognized as something special by Charles Darwin, who stood up for their protection, and Sir Julian Huxley wrote: “Aldabra is one of the treasures of nature and should belong to the whole world.”
