Can physical closeness measure variation and change in pair association strength in captive geckos?

Pair bonding is a key social behaviour but remains understudied in reptiles despite a growing body of evidence suggesting that some species exhibit complex sociality. The lack of evidence regarding the expression of pair association in social lizards species hampers our understanding of its effects on captive welfare. As a first step towards a better understanding of pair related social behaviour in lizards, we investigated if physical closeness, a measure often used to qualify pair bonding in mammals and birds, can be used to assess pair association strength in captive tokay geckos (Gekko gecko). We analysed how physical closeness is related to measures of spatial behaviour collected through scan sampling across two sampling years. Physical closeness was not related to movement but to hiding and basking behaviour, albeit not consistently across years. We also show that although on average our measure of pair association strength did not change across the experimental period, individuals that were paired with new individuals in 2024 exhibit a change. If differences in pair association also occur in the wild and if they confer different fitness outcomes is unknown. However, our results have implications for captive welfare and we propose to monitor socially housed individuals closely to avoid unnecessary socially induced stress.