Attempted predation of a cave olm Proteus anguinus by a dice water snake Natrix tessellata, in Bosnia and Herzegovina

The blind European cave salamander or olm Proteus anguinus is a large and slender neotenous salamander, only found naturally in the western Balkans (Speybroeck et al., 2016). Their maximum length varies according to which river basin they inhabit but is typically 25–55 cm. They are characterised by their pinkish-white colouration, paddle-like tail, and reduced number of digits on all four limbs. The species inhabits both flowing and stagnant subterranean waterbodies in karstic limestone formations throughout their range, as long as these are chemically unpolluted waters, with a stable temperature range of 8–15 °C. Proteus anguinus are almost always observed in caves, for which they have a number of adaptations to allow them to survive such a challenging environment (Hervant et al., 2001; Issartel et al., 2009; Balázs et al., 2020). Due to their specialised adaptations to subterranean life, P. anguinus are particularly vulnerable to changes to the karst ecosystems they inhabit, such as contamination from anthropogenic sources (Kolar, 2019). The European cave salamander also has no known predators within its natural underground habitats.