Using a low-cost trackball system to assess repeatability of movement in small animals

Individual differences in movement patterns are increasingly recognised as important within ecology. In the laboratory, they are, however, often quantified through relatively coarse measures. We describe a low-cost trackball system that incorporates a 3D-printed holder, a commercially available polystyrene ball, and is implemented with open-source software. We used this system to record six parameters of walking behaviour (e.g., translational velocity, total rotation) and tested the hypothesis that these walking parameters are repeatable across individuals. We tested 30 ground beetle individuals, Carabus problematicus, each in two trackball trials one week apart. Individuals were repeatable and differed consistently in several movement parameters (including distance walked, translational velocity, and path straightness), but not in others (e.g., total rotation and sinuosity). Trackballs allow quantification of walking parameters for a wide range of animals, enabling identification of in..., , # Using a low-cost trackball system to assess repeatability of movement in small animals

We developed an inexpensive, open-source trackball setup to measure six walking parameters in *Carabus problematicus*. Across repeated trials, individuals showed consistent differences in traits such as distance walked, translational velocity, and path straightness. Trackballs thus provide a powerful tool for detecting individual variation in movement and behaviour.

#### Description of the data and file structure

**Data_Trackball_Carabus_Problematicus.txt**: 

* id: identity of individual
* date: date of trial
* trial: trial series (first or second)
* species: Carabus problematicus
* sex: sex of the tested individual (M, male; F, female)
* temperature: ambient temperature during trial (degree C)
* total_translation: total distance moved during trackball trial (cm)
* v_translation_mean: translational velocity during trackball trial (mean; cm/s )
* sinuosity: sinuosity (straight-line distance betwe...,