One of the challenges of studying the ecology of an island is uncertainty about past events. Be it twenty years, two hundred years, or two million years ago, it is impossible to go back in time to witness the first arrival of a plant or animal species. Instead, our understanding is informed by whatever historical and biological data is available.
When it comes to the Red-footed Tortoise in the Lesser Antilles, there are a few possibilities. It could have arrived on its own, floating on a raft of vegetation to each island. It could have been brought by Amerindians from South America and introduced to the islands they visited. It even could have been introduced during the colonial era or the modern era.
On St. Martin, we can probably rule out the last possibility. In 1658, Charles de Rochefort published an account of his time in the Caribbean which mentioned the presence of tortoises in the forest on St. Martin. Only settled in the 1620s, it seems likely that tortoises were living on the island before it was colonized by Europeans.
Was the Red-footed Tortoise brought to these islands by Amerindian people? Many believe this is the most likely scenario. The Arawak and Carib people migrated from northern South America—where the Red-footed Tortoise is a native species—to the Lesser Antilles. It would have been very practical to bring the tortoises with them and release them, creating a renewable food supply.
There are also reasons to believe the tortoise did not arrive on its own. Most of the reptiles that colonized the Lesser Antilles by their own means diverged into different species on each island or group of islands. The Red-footed Tortoise seems essentially the same throughout the Caribbean. This suggests it arrived recently.
Also, we know what can happen when tortoises on islands: they become giants, like the tortoises of the Seychelles and Galápagos. It would be reasonable to guess that tortoises colonizing Caribbean islands millions of years ago would have ample time to become giants.
As it turns out, we don’t need to guess that giant tortoises could exist in the Caribbean. About 40 miles from St. Martin, Sombrero Island was once home to the Sombrero Giant Tortoise. Remains of this tortoise were found in guano extracted from the island. Several other extinct species of giant tortoise are known from other parts of the Caribbean. It is possible that existing populations of giant tortoises were hunted to extinction by the earliest humans who arrived here and then replaced by the tortoises we see here today.
You can learn more about the Red-footed Tortoise and other species introduced to St. Martin at Amuseum Naturalis, located at 96 Boulevard de Grand Case. The museum is free and open 4-8pm on Tuesdays and Thursdays. Get more info at http://amuseumnaturalis.com.
