Occurrence in Surface of the Olm (Proteus anguinus) Suggests to Approach Cave Biology Processes with More Flexibility

Photo 1. Different adults of Proteus anguinus active at night (likely looking for prey) in a surface marsh-like environment fed by a spring (the spring mouth is visible on the left) in Doberdò del Lago (northeast Italy). The spring mouth opens on a deep hollow in the mud that during surveys always showed water inside. However, only occasionally, the water level overcomes the spring mouth and floods the surrounding environment. Photo credit: Raoul Manenti. Photo 2. The occurrence of Proteus anguinus on the surface was recorded in 15 out of 69 springs sampled. Panel A shows the first individual of P. anguinus that we observed in spring during the study. As shown in panel B, the occurrence was also recorded during the day. Photo credit: Raoul Manenti (left panel), Edgardo Mauri (right panel). Photo 3. During the study we sampled not only springs but also 10 caves where Proteus anguinus was detected during both night and daytime. In panel A two of the authors (VZ and BB) try to locate P. anguinus after having descended a natural well in the study area. In panel B a typical groundwater-dwelling individual of P. anguinus is shown. Photo credit: Raoul Manenti (left panel), Gentile Francesco Ficetola (right panel). Photo 4. Many of the springs where Proteus anguinus was recorded showed strong variations in water level. In panel A, a typical "estavella" spring is completely dry during February 2022. This is a spring that emits water when the groundwater level rises in the "polje," but absorbs water when the surface water level decreases. A polje (called also karst polje or karst field) is a large, flat depression within karst limestone areas that can be subjected to strong variations in the groundwater level. In panel B, the same spring is completely submerged along with the whole polje in which it occurs (February 7, 2021). Photo credit: Raoul Manenti. These photographs illustrate the article "Wandering outside of the Styx: Surface activity of an iconic subterranean vertebrate, the olm (Proteus anguinus)" by Raoul Manenti, Matteo Riccardo Di Nicola, Veronica Zampieri, Giorgio Grassi, Thomas Creanza, Edgardo Mauri, Gentile Francesco Ficetola, and Benedetta Barzaghi published in Ecology. https://doi.org/10.1002/ecy.4252