The entire Mauritius kestrel population was once four birds, hunting over these ravines in the island's southwest, and four cannot rebuild a species — so Carl Jones's team borrowed a trick from falconry. They lifted the first clutch from a wild nest and hatched it in incubators. Robbed of those eggs, the pair laid again and raised the replacement themselves — twice what a season should give. The hand-reared young went back into the gorges, and later pairs nested in boxes on the cliffs. The same arithmetic was run again for the pink pigeon. Nine endemic birds hold these slopes. On the upland trails they reach you as sound first: the deep call of a pigeon, or the harsh ripping screech of an echo parakeet, a parrot once down to fewer than twenty birds.
Barely two per cent of the native forest of Mauritius is still standing, almost all of it here: low, wind-clipped, often inside cloud. From the Pétrin entrance a few minutes on foot put you at the first lookouts, where ravine after forested ravine folds toward the coast and the flat-topped basalt block of Le Morne closes the view. By early afternoon grey cloud shuts the drop off, so the rim is a dawn matter. Below the rim the trails take you down into humid forest, to a wall of stripped basalt with water coming over the lip — in winter a thread the wind pulls sideways, after summer rain a loud white curtain. A short steep path reaches 828 metres, a modest lump of rock from which you take in the whole island. And here the method runs out. Chinese guava grows into thickets so dense that no native seedling gets light beneath them. From April families drive up to Plaine Champagne and strip the fruit into buckets — the one weed anyone is encouraged to take. Inside the fenced plots the rangers pull it out by hand and the seedlings come back. Outside them the macaques, the pigs and the deer eat the same fruit and drop the seeds where no person ever walks.