Bats as ecosystem engineers in iron ore caves in the Carajás National Forest, Brazilian Amazonia

Abstract

Ecosystem engineers are organisms able to modify their environment by changing the distribution of materials and energy, with effects on biotic and abiotic ecosystem components. Several ecosystem engineers are known, but for most of them the mechanisms behind their influence are poorly known. We detail the role of bats as ecosystem engineers in iron ore caves in the Carajás National Forest, Brazilian Amazonia, an area with > 1,500 caves, some holding ~150,000 bats. We analyzed the chemical composition of guano deposits in bat caves, radiocarbon-dated those deposits, and elucidated the chemical mechanisms involved and the role the bat guano has on modifying those caves. The insect-composed guano was rich in organic matter, with high concentrations of carbon, nitrogen, phosphorus pentoxide and ferric oxide, plus potassium oxide, calcium and sulfur trioxide. Radiocarbon dating indicated guano deposits between 22,000 and 1,800 years old. The guano pH was mainly acid (from 2.1 to 5.6). Percolating waters in those bat caves were also acid (pH reaching 1.5), with the presence of phosphate, iron, calcium, nitrate and sulfate. Acid solutions due to guano decomposition and possible microbial activity produced various forms of corrosion on the caves´ floor and walls, resulting in their enlargement. Bat caves or caves with evidence of inactive bat colonies had, on average, lengths six times larger, areas five times larger, and volumes five times bigger than the regional average, plus more abundant, diversified and bigger speleothems when compared with other caves. In an example of bioengineering, the long-term presence of bats (> 22,000 years) and the guano deposits they produce, mediated by biological and chemical interactions over millennia, resulted in very unique ecological, evolutionary and geomorphological processes, whose working are just beginning to be better understood by science. However, the current expansion of mineral extraction activities coupled with the loosening of licensing and cave protection rules is a real conservation threat to the bat caves in Carajás. The destruction of those caves would represent an unacceptable loss of both speleological and biological heritage and we urge that, whenever they occur, bat caves and their colonies must be fully protected and left off-limits of mineral extraction.

A comprehensive procedure for pollen extraction from bat guano deposits in organic and detrital matrices

“…Where there is a paucity of pollen-based paleoenvironmental reconstruction from lake, wetland, and swamp habitats, bat guano deposits provide an additional archive that fill this data for paleoenvironment reconstruction and paleoecology studies. Over millennial timescale, several meters of guano can accumulate on cave floors [43] , representing an outstanding environmental archive that becomes increasingly attractive for palynologist worldwide [5 , 6 , 10 , 35 , 44] .…”

Metagenomic of Liver Tissue Identified at Least Two Genera of Totivirus-like Viruses in Molossus molossus Bats

“…Their ability to fly long distances and their diverse feeding habits make it easier for them to acquire and spread viruses across remote areas and to transmit them to other species. Additionally, their social structures and behaviors contribute to virus transmission and persistence within bat populations [ 4 , 18 , 19 , 20 ]. However, changes in the environment, such as urbanization, agricultural intensification, and deforestation, have altered the composition and dynamics of bat communities [ 21 ].…”

“…Studies have shown an overall decline in species richness and relative abundance associated with urbanization [ 22 ]. Nevertheless, insectivorous bats tend to thrive in large urban environments [ 4 , 18 , 19 ]. Furthermore, the diversity of bat habitats can influence both microbe transmission and persistence in bat communities [ 2 , 22 , 23 , 24 ].…”