Murtagh, K., Farnworth, M. J., Brilot, B. O. 2020. The scent of enrichment: Exploring the effect of odour and biological salience on behaviour during enrichment of kennelled dogs. Applied Animal Behaviour Science 223, 104917.

Worldwide, millions of dogs are held in kennels for extended periods of time and may experience compromised welfare. Enrichment, often using toys, is considered important to minimize the negative impacts of kennelling. However, the value of this enrichment may be based on various sensory facets of such toys and untangling the relative contributions is a residual challenge. Therefore, improving the utility of toys as enrichment is contingent on an improved understanding of the relationship between the properties of a toy and a dog's interaction with it. The present study aimed to evaluate the addition of two different scents to toys, both presumed to have a different level of biological salience. The behaviour and level of toy engagement of 44 singly housed dogs in a rehoming centre was compared amongst no-toy (NT), unscented-toy (T) and scented-toy (T+) treatments. For T + two scents were used: rabbit (T + R) and lavender (T + L). Toys were colour and type-matched for each treatment. Many of the datasets were zero-inflated therefore a Hurdle analysis was used to explore the relationships amongst the treatments. Non-zero inflated behavioural data were analysed using a Linear Mixed Model to discern treatment effect. Dogs were significantly more likely to interact, and interacted for longer, with scented toys. This was both in comparison to periods when only unscented toys were present and when both scented and unscented toys were simultaneously presented. However, there was no difference in response to the rabbit or lavender scented toys. Provision of scent also significantly reduced stress related behaviours and increased exploration. However, alterations in behaviour were not directly related to likelihood or amount of toy use, suggesting the scents were altering behaviour through means other than increasing physical enrichment use. These findings suggest that augmentation of toys using scents may improve engagement of dogs with them, and positively affect behavioural welfare indicators in the kennelled environment. The use of novel scents may therefore promote better welfare in kennels irrespective of their presumed biological salience, but differing scents should be further trialled.