Does enrichment improve reptile welfare? Leopard geckos (Eublepharis macularius) respond to five types of environmental enrichment

Animal welfare is a high priority for pet owners and accredited zoos and aquariums. Current approaches to measuring welfare focus on identifying consensus among behavioral and physiological indicators of positive and negative emotions. Environmental enrichment is a common strategy used to improve the welfare of captive animals. In enrichment programs, knowledge of an animal's ecology and individual history are applied to modify the animal's current environment and management to increase environmental complexity, make the environment more functional or natural, and increase behavioral opportunities. While enrichment techniques for primates and large mammals are well-studied, reptile enrichment has received little attention to date despite a few promising studies. In this study, we monitored the responses of 16 leopard geckos to five types of enrichment (Thermal, Feeding, Olfactory, Object, and Visual) using a repeated-measures design. We measured both specific behaviors we expected to change in response to each enrichment type and four behavioral indicators of welfare: exploratory behavior, species-specific behaviors (behavioral thermoregulation and hunting), behavioral diversity, and abnormal repetitive behaviors. We found geckos interacted with all five types of enrichment at above-chance levels (i.e., no 95% CIs for engagement time overlapped with 0 s). Geckos spent more time interacting with Thermal and Feeding enrichment than the other types (F(4,60) = 49.84, p < 0.001). Thermal, Feeding, Olfactory, and Object enrichments (but not Visual enrichment) changed specific relevant behaviors (e.g., Thermal enrichment altered thermoregulatory behaviors, Wilk's lambda = 0.25, F(3,13) = 13.39, p < 0.001) and improved behavioral indicators of welfare (e.g., behavioral diversity, Wilks' lambda = 0.30, F(12,178) = 12.31, p < 0.001). These results suggest that geckos respond to environmental enrichment, that their responses are predictable based on their ecology, and that environmental enrichment improves gecko welfare. As in mammals and birds, enrichments that address behavioral needs (here: thermoregulation and feeding) appear more effective than enrichments that simply provide novel stimuli to increase exploration. The extent to which our results can be generalized to other reptile species awaits further study, but we suggest that enrichment should be more widely used to improve reptile welfare.