Tracks and signs are very useful for detecting medium and big mammals, which usually are out of sight. These are helpful tools on field investigation, provide detailed information on the identity and activities of an animal in a place, and can provide us indications of their habitat use (Aranda, 1981a; Navarro & Munoz, 2000; Villalba & Yanosky, 2000). In this paper we characterize the habitat use of medium and big land mammals in Los Mangos forest. We use an observation and track tramp transect, and a modification of the Habitat Suitability Index (HSI) for evaluating habitat suitability. We detect six burrows, four footprints and five Seje palm (Oenocarpus batagua) feeding places, in addition to ten tracks compiled along the other days of field investigation. We recognized ten species of mammals which belong to five orders, using tracks and bitted fruits. The HSI calculated was 7.30 on inner forest, indicating that the habitat is appropriate for animals which use burrows. Resources like food (insects, fruits and preys), refuge, water and resting places converges generating favorable environment for immigration and residence of insectivore, frugivore and carnivore mammals. The fertile plane forest is an important habitat of this area because present there. It offers quality resources to the animal species in there.