Environmental enrichment impacts discrimination between familiar and unfamiliar human odours in snakes (Pantherophis guttata)

Environmental enrichment has been found to significantly influence the cognitive abilities of a variety of mammalian and avian species, with effects ranging from positive to negative, however, these effects have been little studied in reptiles. This is problematic given their popularity as pets and the wide variation in their care. Therefore, the aim of this study was to examine how exposure to environmental enrichment affected discrimination between familiar and unfamiliar humans in a popular species of pet reptile, the corn snake. Snakes (n = 11) were individually housed for four weeks in either an enriched or standard environment before we tested their discrimination between familiar and unfamiliar odours of humans (familiar handler vs. unfamiliar stranger). The snakes were then swapped into the other housing treatment (either enriched to standard, or standard to enriched) for a further four weeks before being tested again. In the discrimination tests, the snakes were simultaneously presented with the odours of a familiar and unfamiliar human within a test arena, and the time spent in close proximity to either stimulus was recorded. We found that after being housed in the enriched enclosures the snakes spent significantly more time investigating the unfamiliar human odour, suggesting successful discrimination of the handlers, and an attraction to novelty. In contrast, snakes housed in the standard enclosures did not discriminate between the two odours despite exploring the stimuli for the same overall amount of time. Therefore, this study demonstrates that corn snakes can recognize the odour of familiar humans; however, this was only observed in the enriched group, suggesting that the absence of environmental enrichment may interfere with discrimination in this task. We recommended that enclosures incorporate enrichment in order to promote good welfare.