Craugastor loki is the dominant amphibian in the Los Tuxtlas tropical rainforest. We recorded 1 251 individuals (58% adults) in a sampling year within a great variety of microhabitats in 6 forest fragments. Although C. loki is considered tolerant to habitat disturbance, 71% of all gravid females were found in most highly conserved sites. Gravid females were mostly found in the largest forest fragment with continuous rainforest (473 ha), preferring habitats with distances to the edge over 50 m, soils with high leaf litter cover and depth, high understory density, high relative humidity but independent of the distance to water bodies. Gravid females, a critical element to maintain the species, are very vulnerable to habitat loss and edge effects. A change in conserved habitats may affect C. loki abundance and population structure, potentially seriously disrupting the trophic chains and community structure of the rainforest.