Guano

Guano has an exceptionally high content of nitrogen, phosphate and potassium, so it has been used widely as manure. The characteristic microscopic appearance of fresh guano is a bedded spongy or aggregated microstructure and vughy porosity. Types of guano particularly enriched in plant organic remains, like fruit-bat guano, consist of dark to black fibrous fragments of amorphous organic material. Identification of the presence of past guano deposits has several implications for the archaeological record. In caves, massive guano deposits related to intensive bat roosting are regarded as a general indication of human absence. Furthermore, guano-related alteration features can provide valuable stratigraphic information. The presence of recognizable guano crusts and other guano deposits indicates stable surface exposure with lack of sedimentation. Future studies should focus on studying several phosphatic features, although the vast amounts of different bird species nesting in caves makes this endeavor quite difficult.