To advance conservation in the increasingly fragmented landscape of Madagascar, we must examine the persistence and interactions of species in human-disturbed habitats. I investigated lemur-predator interactions in southeastern Madagascar through a comparison of predator communities and anti-predator behaviors of Milne-Edwards' sifakas (Propithecus edwardsi) in the continuous rainforest of Ranomafana National Park, and the forest fragments of Ialatsara Forest Station. I confirmed the presence of potential aerial predators at each site, but the sifakas' confirmed native mammalian predator, fossa (Cryptoprocta ferox), was absent from the fragmented site. Playbacks of predator vocalizations did not suggest that fragment-living sifakas have weakened anti-predator responses, but that their responses may be less specific than those of conspecifics in the continuous forest. I found that fragment-living sifakas displayed less downward vigilance and more frequently used low canopy heights; these behaviors may increase their vulnerability to recolonizing ground predators. I investigated local ecological knowledge (LEK) of carnivore ecology in communities 0–20 km from continuous forest to explore the potential for such recolonization. My findings from 182 interviews in 17 communities suggest that the fossa is especially sensitive to anthropogenic disturbance; it was only observed in communities ≤ 2.5 km from the continuous forest within the last five years. In contrast, the introduced small Indian civet (Viverricula indica) and wild cat (Felis silvestris) were distributed ubiquitously and displayed an affinity to human-dominated habitats. LEK surveys can provide information on the poorly understood responses of the Malagasy carnivores to the threats they face in a changing landscape.