Behavioral observations of the olm (Proteus anguinus) in a karst spring via direct observations and camera trapping

Abstract

The olm (Proteus anguinus), an endemic amphibian of the Dinarides’ underground waters (Europe), is one of the world’s most widely known subterranean species. Although various aspects of olm biology have been extensively studied, the data on their behavior in the wild remain scarce mostly due to inaccessibility of their natural habitat. Yet, olms also occur in several karstic springs during nighttime. These are easier to access and present an exciting opportunity to study olm behavior in nature. Here, we report on systematic observations of olms in one such spring in Slovenia, where we observed them for nine consecutive summer nights, coupling direct on-site observations with IR camera trap recordings. We used IR camera trap recordings to construct simple ethograms, as well as to quantify olm movement activity by video-tracking. Olms regularly occurred on the surface during the night, and dawn appeared to be a key stimulus for their retreat underground. They were constantly active, but rarely swam far from the spring. Despite the short-term nature of the study, we collected new occurrence and movement data, and at the same time tested the usability of IR cameras for surveying olm presence and behavior in nature. Experience gained through the study may prompt long-term and more complex behavioral studies using similar approaches.

Wandering outside of the Styx: Surface activity of an iconic subterranean vertebrate, the olm (Proteus anguinus)

“…To date, very limited observations of olms outside caves are available (except for the black olms), and are attributed to individuals accidentally washed out of groundwater (Lanza et al, 2009) or to accidental movements occurring during nighttime at a single site along the groundwater–surface interface (Premate et al, 2022). So far, the possibility of active exploitation of surface habitats by troglomorphic populations has seldom been hypothesized (Bressi et al, 1999), and has remained without empirical evidence.…”