Monitoring Elephant Activity Patterns in a Zoo Using Co-located Seismic and Infrasound Sensors: A Pilot Study

This pilot study evaluates the feasibility of recording low-frequency elephant rumbles at the Opel-Zoo near Frankfurt am Main, Germany, using non-invasive co-located seismic and infrasound sensors. Wave-based communication of African elephants (Loxodonta Africana) is well-documented, but its study in anthropogenic zoo environments - particularly with respect to seismic signals - remains limited compared to natural habitats. Over a period of several weeks, we recorded thousands of rumbles that reveal significant temporal variability. Rumble activity exhibits a diurnal correlation with visitor numbers, while many rumbles occur in rapid sequences, suggesting interaction and potential communication among the five elephants housed in the zoo. Additionally, most rumbles are accompanied by ground vibrations, resulting from locomotion or trampling, which are not detectable through sound-only measurements. This underscores the advantages of integrating seismic and acoustic data, revealing that rumbles rarely occur as isolated events. Moreover, this study identifies potential external factors that may trigger increased rumble activity. The collected dataset provides promising insights into temporal elephant activity, helping to deepen our understanding of their behaviour and welfare in zoo environments that are highly influenced by anthropogenic conditions.