I first heard of Ile aux Aigrettes at a conference on island pest eradications held in Auckland in early 2001. A delegate from Mauritius spoke about a failed attempt to eradicate Indian musk shrews from the 25 ha island, which had already been cleared of feral cats and ship rats.
The island next registered in my consciousness a decade later, when I was researching examples of extinct species being replaced with living relatives (sometimes referred to as ‘de-extinctioning’, or ‘taxon substitution’). I had been involved with a translocation of Snares Island snipe to an island off Stewart Island in 2005, to replace a snipe that became extinct in 1964. During write-up of the successful follow-up survey (in 2011), I concluded that introduction of Aldabran giant tortoises to Ile aux Aigrettes (to replace extinct Mauritian giant tortoises) was the best studied taxon substitution to date. After such a prolonged build up, I knew that a visit to the island would be a highlight of my time in Mauritius.
Ile aux Aigrettes is a low-lying, almost circular island lying about 800 metres off the south-east coast of Mauritius. It is leased and managed by the Mauritian Wildlife Foundation, which has worked for the past three decades to restore an example of dry lowland Mauritian forest, including reintroduction of lost plants, birds and reptiles. Among the endangered plants on the island, the endemic ebony tree Diospyros egrettarum has benefited from introduction of the giant tortoises, which eat its fallen fruit and thereby spread and fertilise its seeds.
Two rare lizard species from Round Island (23 km north of Mauritius) have been reintroduced to Ile aux Aigrettes, including the impressively large Telfair’s skink (Leiolopisma telfairi). This skink has an unlikely (and ultimately unfounded) connection with New Zealand, as until 1995, most New Zealand skinks were also placed in the genus Leiolopisma. It required application of molecular techniques plus a careful examination of morphological features to reveal that the physical similarity between the Mauritian species and New Zealand skinks was due to convergent evolution (rather than any close relationship) and that New Zealand skinks should be placed in the resurrected genus Oligosoma.
In addition to the giant tortoises and lizards, several endemic bird species have been reintroduced to Ile aux Aigrettes. The Mauritius kestrels soon flew back to the mainland, but pink pigeons, Mauritius olive white-eyes and Mauritius fodies are now more readily seen on Ile aux Aigrettes than on the main island, where they are exposed to predation by introduced crab-eating macaques, small Indian mongooses, feral cats and rats. The fodies are particularly abundant and confiding on the small island, readily entering buildings in search of anything edible.
The project that I was most interested to see and discuss on Ile aux Aigrettes was their attempts to reintroduce seabirds – an area of conservation research that has been a major focus in New Zealand over the last two decades. About 200 chicks of six species (red-tailed tropicbird, white-tailed tropicbird, common noddy, lesser noddy, sooty tern and wedge-tailed shearwater) have been moved to the island over the past 6 years, and hand-fed until they completed their feather-growth and flew out to sea. Sightings of several species have increased on the island since the project started, but the team are still waiting on confirmation of the return of one of their banded chicks.
Te Papa curator of vertebrates Dr Colin Miskelly visited Mauritius on his way back from the French subantarctic territories of Crozet and Kerguelen Islands. His visit to Ile aux Aigrettes was hosted by the Mauritian Wildlife Foundation.