We established basis for a datetelling method of leaves (Tillandsia spp.) consumed by Tremarctos ornatus by determining or detecting the presence of microorganisms. We used samples from the field that corresponded to different states of decomposition. The samples (2 cm from the leaf base consumed by the animal) were processed in the laboratory, characterized and determined. Cocobacilli (Pseudomonas sp.) and negative bacilli Gram were the most common bacteria morphotypes, the first were founded on samples from all ages and the second on samples no older than six months. Positive cocobacili Gram (Bacillus sp.); were just present in samples between one and three months old. Positive Gram bacilli occurred only in samples no older than a month, cocos and diplococos in samples between five and six months. Four fungus morphotypes were found, two of them being Mucor sp., and Trichoderma sp., in addition to Epicoccum sp., Alternaria sp., Rhizoctonia sp. Trichoderma was associated with at least one more kind of fungus, for samples to older than one month, but no older than five months.