rainy weeks and to be much less active the rest of the year. For example, five-foot-long Leioheterodon snakes pass the dry months several feet below ground, curled up in a nest of ants, and emerge only after the rain begins. Similarly, many of Kirindy's birds spend the harsh months in other parts of Madagascar or in Africa or Europe. None of these pattern are surprising. Many birds migrate, and many of the world's frogs, lizards, and snakes lie low during cooler periods of the year. Some of the lemurs and other mammals Kirindy, however, are quite another story, a striking exception to the rule that tropical mammals generally do not exhibit strong seasonal variations in activity. Most puzzling among them are several species that hibernate even when the weather is warm. Verreaux´s sifakas (Propithecus verreauxi verreauxi) are the most prominent inhabitants of Kirindy. These long-legged, seven-pounds lemurs, white with dark patches, leap among tree trunks high in the canopy, propelled by their powerful hind legs but continually maintaining an upright posture. Like the vast mjority of primates elsewhere in the world, they live in small, cohesive groups of two to eight members and are active exclusively during the day. Sifakas have teeth and guts that are specialized for feeding on leaves, but they adapt their menu opportunistically as different flowers and fruits come into season. These lemurs cope with the long dry season primarily by expending less energy, sometimes having the distance they travel each day and the time they devote to foraging and other activities. Sifakas´ body temperature falls a few degrees at night, another calorie-saving adaption;