National Geographic : 2009 Nov
canyons. Lemurs like the white-furred Decken s sifaka and the brown lemur use the tsingy as a kind of highway, leaping from spire to spire as they travel between fruit trees. In slots and crevices lizards chase insects through gardens of drought-tolerant xerophytes---euphorbias, aloes, spine-covered Pachypodium, and other plants that drop long, cablelike roots into the rock searching for water. In the middle ranges of the high-rise, more niches appear in the canyon walls. Large fruit bats and dark vasa parrots roost here, their cack- les and cries echoing through vaulted chambers and crumbling galleries. In shadier spots, bees anchor their nests in holes in the stone. But it is in the humid grike bottoms, where water and soil collect, that the environment is richest. Here, among arrays of orchids and enor- mous tropical hardwoods, roams a bestiary: giant snails and fist-size, cricket-like insects, large chameleons, emerald green snakes, and red rats. e lemur-eating fossa---a wiry, thin-coated mammal with retractable claws that resembles something like a large cat---also patrols the tsingy. Finally, below the soil and the mud are caves and tunnel passages, the subway system where sh, crabs, insects, and other creatures live and commute, some without ever surfacing. This walled city has sheltered its residents even as Madagascar s other ecosystems disinte- grated. Scientists call it the perfect refuge. " " in biology signi es a safe zone, like a refugee camp, to which living things withdraw as their habitat shrinks. Once they become cloistered in refuges, animals and plants o en become increasingly distinct from even their close relatives. Madagascar itself epit- omizes this process, so unusual and removed are many of its species from their cousins on the African continent. Lemurs are the island s best known creatures. Their precursors once inhabited Africa but eventually went extinct there, leaving the continent to other primates, Vertical pupils identify a seseke, or leaf-tailed gecko, as a nocturnal creature. Its camouflage works so well that the lizard doesn't hide during the day. It simply flattens itself against tree trunks while waiting for darkness and insects to eat.