Slow but steady – Giant tortoises help clear invading species from island paradise

24 March 2006 | News story

Conservation needs all the help it can get. On the beautiful Mauritian island of Ile aux Aigrettes, some unlikely assistance is being provided by giant tortoises which are happily dining on invasive weeds that are threatening the island’s natural balance.

Ile aux Aigrettes, a 26ha offshore islet, harbours Mauritius's last remnant of coastal ebony forest but is under constant threat of degradation from invasive plant species.

Following its declaration as a reserve in 1965, the island continued to degrade until a restoration project to remove invasive alien species and re-establish native ones began in 1985. Now 80% of the island’s forests has been restored.

The island reserve is home to a fifth of the world’s population of the Endangered pink pigeon and is equipped with a native plant nursery that produces 45,000 plants each year.

A grant from the Sir Peter Scott Fund for Conservation Action of IUCN’s Species Survival Commission (SSC) is helping complete the restoration work, safeguarding this unique habitat and its associated threatened wildlife. The project involves members of SSC’s Indian Ocean Island Plant Specialist Group.

Before the arrival of people on Mauritius, two tortoise species existed, but their use as a ready source of protein for passing sailors pushed them to extinction. The Aldabran tortoise (Geochelone gigantea) on Ile aux Aigrettes is the nearest relative of the lost species and has been introduced to fill the role as herbivore in the ecosystem.

The tortoises are helping control weeds as they have an appetite for particular exotic and invasive species. As the only free-roaming population of giant land tortoises in the Mascarenes, they also help disperse the seeds of native plants such as ebony and bois clou.

At the end of 2004, only 5ha of the island remained unweeded. Weeding and replanting native species in this last section began this year and will be completed in 2006. General maintenance weeding will continue indefinitely.

The work carried out so far has rid the island of some highly invasive species of plants such as prunier malgache, acacia geant, and tecoma whilst native species to benefit include ebony, bois de boeuf, and bois chenille.

A team of 40 labourers who previously worked for a local sugar estate but had accepted voluntary retirement, were recruited for the work. The project benefits from their previous experience of working on the island while they have learned new skills.

For further information contact:

Andrew McMullin, IUCN/SSC Communications Officer, mcmullina@iucn.org; Tel: +41 22 999 0153


This image shows the courtship behavior of Indian Bull frogs (Holobatrachus tigerinus). During the monsoon, the breeding males become bright yellow in color, while females remain dull. The prominent blue vocal sacs of male produce strong nasal mating call.