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The Recovery of Tromelin Island

Islands can have strange histories but few are more obscure than that of Tromelin Island of the Îles Éparses in the Western Indian Ocean. Tromelin Island is a tiny speck in the ocean located about 450 kilometres east of Madagascar. This 97 hectare sand bank was discovered quite late in the piece by the French in 1722, and it remained relatively undisturbed, including free from introduced mammals, until 1761. Tromelin’s history took a turn for the interesting here when the French slave ship L’Utile arrived.

Aerial view of Tromelin Island
Aerial view of Tromelin Island, Western Indian Ocean (Photo by Lucia Simion).

Tromelin Island had would have had up to eight species of seabirds breeding on it when the slave ship L’Utile wrecked upon its northern reef. The hundreds of survivors of the wreck somehow overcame the odds to work together and dig a well and create a shelter. Within the year a makeshift boat was salvaged from the remains and the white crew sailed away to providence, promising to return for the 60 remaining Malagachy slaves. However, this was not to be, at least not immediately. It wasn’t until 1776 that another French ship La Dauphine arrived to find only 7 surviving women and one 8 month old child. Between 2006 and 2013 French archaeologists reconstructed the daily lives of these survivors.

Nesting red-footed boobies
Nesting red-footed boobies on Tromelin Island (Photo by TAAF).

The island remained unvisited again until the English hunter Layard arrived in 1856. Although introduced mice were present around this time the larger Norway rat did not arrive until afterwards. The French established a météo (weather) station in 1954. With each encounter with humans the seabird populations on Tromelin Island dwindled to only two booby species until their fortune changed in 2005 when French scientists from Le Réunion arrived to eradicate the mice and rats. Although unsuccessful at eradicating the mice the eradication of Norway rats was successful, and the island began to flourish once again.

The first brown booby
The first brown booby recolonising Tromelin Island (Photo by TAAF).

Since 2007 the island has been administered by the Terres Australes et Antarctiques Françaises (TAAF). Following rat eradication the vegetation has recovered from being the staple food source of rats. Three seabird species have returned to breed on Tromelin; the white tern, brown booby, and brown noddy. Red-footed and masked boobies have increased rapidly in numbers, particularly because with no more predation of their chicks they can remain longer and safer on the island raising their offspring. The island is now one of a number of important reference ecosystems for environmental research, and one of many islands in the Western Indian Ocean which has benefitted from mammal eradications leading to spectacular recovery of species and ecosystems.

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