Tortoises of Madagascar

The radiated tortoise takes its name from the pattern radiating across each plate of its domed shell, bright yellow lines fanning out over dark ground, one of the most striking shells of any tortoise on Earth. It once ranged widely across the dry spiny forests of southern Madagascar, sharing the octopus-armed Didierea trees and the sun-baked ground with the rest of that region’s stripped-down desert-adapted life.

A pattern so distinctive it became the reason the species is disappearing.

That same beauty made it one of the most trafficked tortoises in the world, illegally collected for the exotic pet trade despite legal protection. In April 2018, Malagasy authorities seized ten thousand radiated tortoises from a trafficker’s house near Tuléar, then another seven thousand months later in nearby Betioky, all bound for the pet trade in Asia. The traffickers were sentenced to six years in prison and fined twenty-six thousand dollars, a rare case of the scale of the crisis actually being matched by the scale of the response.

Conservation breeding programs, including one at the Arboretum d’Antsokay, now work to hold a captive population as insurance against further collapse in the wild.

The angonoka, or ploughshare tortoise, is the largest and rarest of Madagascar’s terrestrial tortoises, confined to a small pocket of deciduous forest near Soalala and Baly Bay in the west. Its name comes from the long spur curving upward from the front of its shell, a plough-share shape the males use to fight rivals and court mates. With fewer than 300 individuals left in the wild, it is not simply endangered. It is, by most counts, the rarest tortoise on the planet.

Its ornate shell, precisely the feature that makes it recognizable, is also what dooms it: a single angonoka shell can fetch up to fifty thousand dollars on the black market. Poaching, combined with nest predation by introduced bush pigs, has pushed the species to the edge closely enough that in 2015 the Durrell Wildlife Conservation Trust and the Malagasy government took a drastic, almost paradoxical step: deliberately defacing the shells of the remaining wild tortoises to make them less desirable to poachers.

A shell disfigured on purpose, to save the tortoise wearing it.

For nearly twenty-five years, Durrell has run a captive-breeding program for the angonoka at Ankarafantsika National Park, one of Madagascar’s most successful conservation stories in raw numbers, with reintroductions steadily building back the wild population. Because of the poaching risk, visitors can only observe the tortoises through wire-mesh fencing, a small, deliberate inconvenience standing between the species and extinction.

Before the radiated tortoise and the angonoka, Madagascar had giants of its own, two species of giant tortoise, Aldabrachelys abrupta and Aldabrachelys grandidieri, close relatives of the giant tortoise still living today on Aldabra atoll. Subfossil remains found at Antsirabe’s “bains de la Reine” belonged to individuals with shells at least two metres long. Others turn up across the Mahafaly plateau, at Ampoza, Belo-sur-Mer, and Ampasambazimba, everywhere the island’s dry lowlands and highlands once supported them.

These were not marginal animals. As the island’s largest herbivores, they filled an ecological role usually held elsewhere by large mammals, dispersing seeds and shaping vegetation across huge distances. Their disappearance, likely from hunting shortly after humans reached Madagascar, left what ecologists call an evolutionary anachronism: plants and landscapes still bearing the imprint of an animal no longer there to interact with them. At Taolambiby, a fragment of giant tortoise shell, deliberately perforated, recovered in the 1960s, is one of the clearer physical traces of that hunting.

A landscape still shaped by an animal that has not walked it in a thousand years.

The ecological gap is significant enough that some conservationists have proposed introducing Aldabra’s living giant tortoise, the closest surviving relative, as a substitute grazer to help restore degraded habitats, a living stand-in for a giant Madagascar can no longer replace on its own.

Madagascar’s reputation for tortoises understates the real picture. The island holds five terrestrial tortoise species, four of them found nowhere else, alongside four freshwater turtle species and five species of marine turtle passing through its waters, an unusually complete set of chelonian habitats for one island. The freshwater Erymnochelys madagascariensis, the island’s only endemic freshwater turtle and the “big-headed” side-necked turtle, survives in the lakes and rivers of the west despite losing habitat to rice-paddy drainage. In the dry forests around Morondava, the small flat-tailed tortoise, or kapidolo, deals with the harshest months by simply disappearing underground, burying itself in leaf litter and sand to wait out the dry season until real rain returns.

Along the coast, green turtles and hawksbills nest on isolated western beaches, still threatened by egg collection for food in places, while Nosy Iranja, off Nosy Be, remains one of the most accessible nesting sites for hawksbills anywhere on the island, and Nosy Sakatia offers near-guaranteed snorkeling encounters with green turtles. Among the Vezo, sea turtle meat is prepared under specific customary rules, cooked without salt and instead simmered in seawater for its sharp, distinctive flavor, one small example of how deeply this animal is woven into the practical culture of the coast, not only its conservation posters.