Tortoises at 60: the Fregate restoration, explained in numbers

In 1965, there were fewer than one hundred giant Aldabra tortoises on Fregate Island. They were brought there as food animals by passing sailors, a practice that had been reducing tortoise populations across the Indian Ocean for three centuries.

Today there are 3,500.

The arithmetic of that recovery is worth understanding, because it took a specific kind of patience that is increasingly rare in conservation: the willingness to do the same thing, carefully, for decades, without a guarantee that it would work.

The first step was rats. Fregate's resident population of black rats was, by the 1980s, suppressing every ground-nesting bird species on the island. In 2000, the island's owners funded a complete rat eradication programme — a poisoning operation across the entire 219-hectare island that took eighteen months and required the temporary removal of every tortoise, every gecko, and every bird that could be caught. The cost was approximately USD 1.2 million. The result was silence, followed, within two years, by the return of eight endemic bird species, including the Seychelles magpie-robin, which had been locally extinct for decades.

The tortoise population, once the rats were gone and supplemental breeding had been established, began to recover in earnest. Fregate now runs one of the most successful captive-breeding programmes in the Indian Ocean. Hatchlings are raised in protected enclosures until they are large enough — roughly five years and 5 kilograms — that rats, which still occasionally arrive on supply vessels and are immediately controlled, cannot predate them.

The number 3,500 is not a ceiling. It is a waypoint. The carrying capacity of the island is estimated at between 4,500 and 5,000 adults. The programme expects to reach that figure within twelve years.

*Torti* — the tortoise. In Seychellois Creole, to call someone a *torti* is not an insult. It means they take the long view.