Glue-on tri-axial accelerometers code for different behaviours in Eurasian otters (Lutra lutra)

Abstract Characterising the daily behavioural activity of a species is essential for understanding its biology and interactions within the ecosystem. Behavioural activities can be inferred from accelerometers that measure body posture and movement-based proxies for energy expenditure. Eurasian otters ( Lutra lutra ) are erratic and cryptic animals that are difficult to observe in the wild. In addition, they are highly flexible and mobile which would suggest that their behaviours may be challenging to determine using animal-attached accelerometers. In this study, our goal was to classify behavioural activities from animal-borne accelerometer data on otters under human care in zoos. We glued a tri-axial accelerometer (sampling at 25 Hz) onto the fur of three adult male Eurasian otters. We observed the tagged otters for 4–5 days each and recorded their behaviours using video cameras and visual observation. By combining visual behavioural observations with acceleration patterns, we trained an extreme gradient boosting model to classify 13 behaviours during the tracking period based on acceleration. When used on behavioural events new to the model, the model predicted behavioural activities with an overall accuracy of 53.6%, (F1 = 0.506, recall rate = 0.536, precision = 0.538). However, model performance varied considerably between behaviours, and especially stationary behaviours were often not clearly distinguished from one another. Grouping the stationary behaviours, except latrine, increased accuracy to 68.2% (F1 = 0.66). By improving the attachment method with more glue to keep the tag on for longer, this method has great potential to gain novel understanding of the ecological significance of behaviours and energetics in wild Eurasian otters. Especially combined with spatial location, we should be able to answer “what”, “where”, “when”, and “how” wild Eurasian otters allocate their activities. Understanding wild Eurasian otter behaviour, spatial movements and habitat use is expected to have great significance for the conservation and management of this vulnerable species.