Mauritian Olive White-Eye
The Olive White-Eye (Zosterops chloronothus) was a contemporary of the Dodo until 350 years ago1. This small bird, itís about the size of a wren, takes its name from the olive green plumage of its wings, its back and its head while white feathers encircle the eyes gives it its name. To complete your picture, the birdís underbelly is pale white to light cream in colour.
Today, the Olive White-Eye also risks the same fate as the Dodo as it finds itself teetering on the brink of extension. The Olive White-Eye is assessed as Critically Endangered, which is the penultimate step before being classified as ĎExtinct in the Wildí. The threats to the Olive White-Eye are the loss of habitat, both its quality and extent, and introduced mammals2.
Lying to the east of Madagascar, Mauritius is a small island in the Indian Ocean, that is only about one tenth the size of Wales. There arenít any endemic land mammals on Mauritius. From the 16th century onwards, land mammals arrived, initially on the boats of seafarers who released pigs for food on their return journey; and who accidently or not introduced: dogs and cats that went feral; rats; and monkeys from the East Indies. Whilst hungry sailors and some of their fellow imported mammals were responsible for the swift demise of the Dodo, itís the non-native land mammals and substantially reduced habitat that are the predominant threats to the Olive White-Eye.
In the mid-1970s it was estimated that there were 350 pairs of Olive White-Eye, but within 10 years the population had slumped to 275 pairs, and was further reduced to about 200 pairs by the early-1990s. By the turn of the 21st century, the population was estimated between 93 and 148 pairs. It is this point that there was an intervention by initially Jersey (Durrell Wildlife Conservation Trust) Zoo3 and later Chester Zoo4 working with the Mauritian Wildlife Foundation5 . Their plan was to create a natural predator-free enclave for an insurance population of Olive White-Eyes on an off-shore island. Ile aux Aigrettes was chosen, itís a small 26 hectare island about half a mile off the coast of Mauritius.
By 1991 the rats, cats and mongooses previously present on the island had been successfully eradicated paving the way for further work. Once the rats were gone there was a dramatic emergence of Ebony seedlings and programme of systematic weeding of this and other alien plant species on the Ile aux Aigrettes was initiated. By 1985 the Mauritian Wildlife Foundation put a watchman on the island and started restoration work. A weeding programme to eradicate other introduced invasive plants such as the False Acacia and the spiny Prune Malgache was launched.
In the past, Mauritius had 2 species of endemic tortoises, but they became extinct about 200 years ago through excessive predation by man. So in 2000, 18 Giant Aldabran Tortoises were released onto Ile aux Aigrettes to simulate the impact of tortoises browsing on the islandís vegetation. It is the first time that giant tortoises can be seen in this type of ecosystem since the extinction of the Mauritian species. At the moment the tortoises are restricted to a fenced area, but it is hoped that, as soon as the necessary research has been completed and reviewed that the tortoises will be released to roam free throughout the island.
The Mauritius Kestrel was reintroduced for the first time to Ile aux Aigrettes. However, this unique bird of prey would seem to prefer the higher altitudes and terrain of the nearby mainland Bambous Mountains and rarely comes back to the island.
To date 20 endangered endemic plant species have been introduced to the island, including the critically endangered Round Island Bottle Palm and the Round Island Hurricane Palm, of which only one adult tree remains. Hand in hand with these plant introductions, has come the reintroduction of native animals once known to have existed on the island. In 1994, an aviary was set up on the island and the Pink Pigeon was reintroduced on the island. Today there are over 75 pink pigeons flying free, the only wild population of these birds to be seen by the public anywhere in the world.
By 2004 there were still a few of previously introduced the alien animal species present on the island. These included the Indian House Shrew, Indian Wolfsnake and Giant African Land Snails. Their presence acts upon native animal species as either competitors or predators. Currently methods are being looked into for their eventual eradication. The Round Island Telfairís Skink, a clawed lizard, has been brought back in semi captivity, waiting the day for its release on the island when the shrew has finally been controlled.
The intervention for the Mauritian Olive White Eye by the zoos was to collect their eggs, incubate them, then hand rear the chicks before acclimatising then in aviaries on Ile aux Aigrettes, prior to their release. The Olive White Eyes quickly laid a second clutch and were left to rear them themselves. Experienced keepers from Jersey and Chester were responsible for hand-rearing the chicks. The technical and financial support given by Chester and Jersey has been key to the Mauritian Wildlife Foundation restoring a microcosm of Mauritian ecology on Ile aux Aigrettes.
Today, Ile aux Aigrettes is a nature reserve. Visits are carefully controlled and limited to 15,000 per annum. These organised visits include both those made by tourists and educational visits by Mauritian children. Ile aux Aigrettes today is a microcosm, regrettably an incomplete one, of Mauritian wildlife prior to the arrival of man on the island 400 years ago. Nevertheless, the decline in Mauritiusís unique bird, reptile and plant-life has been temporally halted, in part due to the resources of two zoos from the British Isles through their practical support of the Mauritian Wildlife Foundation.
David Lomas, 2013
1 The last recorded sighting of a living Dodo was in 1662. Quammen, David; The Song of the Dodo; ISBN 9780712673334