Our latest study (https://doi.org/10.1016/j.applanim.2024.106484) sheds light on a perplexing behaviour seen in captive reptiles, namely their interactions with barriers (IWB), a form of repetitive behaviour akin to pacing in mammals. As part of her PhD research, Melanie Denommé investigated the motivations behind IWB in bearded dragons (Pogona vitticeps; Figure 1) over a three year period, and formally tested whether it stems from a “desire” to escape their enclosures.

Our findings revealed a strong preference for performing IWB near the front barrier of their environment (Figure 2), the only known escape route; even when half of it was obscured; they also direct more of their behaviour toward the transparent part of the front barrier. Interestingly, IWB was 15 times more likely to occur around the time when lizards defecated, supporting an argument that these behaviours may be driven by escape-related motivations, at least with respect the need to find suitable defecation areas.  However, no clear link was found between IWB and anticipation of feeding, suggesting species-specific differences in how repetitive behaviours are triggered. Despite these results, lizards would still exhibit IWB with non-transparent barriers (Figure 2), suggesting that escape is not the exclusive explanation for these repetitive behaviours.

Seasonal and sex-related patterns offered further nuance. Contrary to expectations, female lizards performed IWB more during spring, while males showed consistent levels year-round. This might reflect frustrated breeding-season motivations, as females in the wild often roam widely in search of mates, a behaviour restricted in captivity. These findings emphasize the complex interplay between natural instincts and captive conditions, highlighting the importance of tailoring environments to better meet the needs of individual animals. By understanding these behaviours and using an evidence-based approach, we can deepen insights into the diverse causes of repetitive behaviours across species and thereby improve captive reptile welfare.

Note that the actual levels of IWB seen were low throughout the study, with numerous animals never performing the behaviour. There appear to be individual differences in the expression of IWB.

Citation

Denommé, M and Tattersall, GJ. 2025. Investigating the motivations of repetitive barrier interactions in Pogona vitticeps. Applied Animal Behaviour Science, 283: 106484. https://doi.org/10.1016/j.applanim.2024.106484