The Life Hidden Inside Caves: Ecological and Economic Importance of Bat Guano

Bats are emblematic hosts of caves. These small flying mammals deserve special attention because their presence has a great economic and ecological impact; they introduce organic matter, the guano, in the ecosystem they live in. Indeed, “guano” (a Quechua word meaning “fertilizer”) is the accumulation of their fecal matter (excreta); its deposition can reach several meters. The composition of guano is influenced by the bat’s food. In addition to its role within the caves, the bat guano is exploited for various purposes; it is used as an effective fertilizer for the cultivation of plants because of having exceptionally high content of nitrogen, phosphate, and potassium and also for the improvement of detergents and other products of great value for humans. The bat guano hosts various classes of microorganisms (viruses, bacteria, algae, fungi, and protists), which are adapted to the cave environment. Since guano is highly acidic, these microorganisms can be considered as extremophiles. They produce functional organic compounds in extreme conditions that could be of interest not only in the drug industry but also in different biotechnological areas. Here, we review already available information on the ecological and economic effects of bats and their guano. We report their food preferences, foraging behaviors, and environmental impacts. Information on these aspects may be useful in finding a solution about protection and preservation of bat populations.