Refinement of tickling protocols to improve positive animal welfare in laboratory rats.

Positive animal welfare emphasises the importance of animals having positive experiences to improve their quality of life. For laboratory rats, tickling is proposed as an effective and practical way to positively improve their welfare. Rat tickling with the human hand was developed to study positive emotions (affect) and ultrasonic vocalisations (USVs) in rats by mimicking playful interactions between rats. The standard tickling protocol involves initial finger contact with the nape of the neck before flipping the rat and gently pinning it in a supine position whilst making rapid finger movements just like in human tickling. Research including our own, has shown that when rats are tickled by a human hand they often produce 50 kHz ultrasonic vocalisations (USVs) which are thought to indicate positive affect in rats. Generally, rats find tickling rewarding as tickled rats are quicker to approach the human hand and can be trained to perform a task for tickling. However, our own research experience of rat tickling, and other available evidence, shows that rats, like humans, vary considerably in their response to tickling. This suggests that there is a risk that some rats perceive tickling as a negative experience depending on how tickling is performed and the rats' individual characteristics. From our data, we estimate that approximately 20% of rats may find tickling a negative experience. This calls for refinement of tickling protocols to ensure that the positive effects of tickling are maximised and to minimise individual differences in response to tickling.

Our overall aim is to increase the uptake of rat tickling as a widely used approach to improving the welfare of the approximately 180k rats used annually in the UK for research purposes. Within this overarching aim, we propose to refine the tickling protocol by measuring male and female rats' affective responses to tickling. To encourage wider uptake of tickling we will study implications of tickling for experimental repeatability and work with end-users to identify and constraints to use of tickling in practice.

Within this overall aim, we will test how different styles of tickling affect the emotional response of rats using recordings of USVs and our validated test of emotional bias. Our hypothesis is that rats will show a more uniform increase in indicators of positive emotion with a 'playful tickling protocol' that emphasises playful interaction between the human hand and the rat, and which also minimises the use of pinning relative to the standard protocol. We also hypothesise that the biological consequences of tickling will be less variable using a playful protocol relative to the standard protocol. This will refine and increase the repeatability of research where tickling is applied either as a standard enrichment or as an experimental treatment. To test this rats will be exposed to a further tickling sessions of their allocated treatment using USV production to assess their emotional responses. After a final tickling session we will contrast the variability in emotional response to the tickling regimes against response measures such as behavioural anxiety and physiological markers for stress and inflammation. In our third objective, we will engage with researchers (who use rats in their work) locally, nationally and internationally to determine the potential of applying tickling as a valid and practical form of positive social enrichment in their laboratories. Our communication plan includes development of a web-site and forming a stakeholder group to understand constraints to use of tickling in practice and to gather data on the wider use of tickling as a research treatment or as a social enrichment.

Tickling rats with the human hand was developed to mimic the interactions of rat play, and is proposed as an effective and practical approach to positively improve laboratory rat welfare. The standard rat tickling protocol involves finger contact with the nape of the neck before flipping the rat and gently pinning it in a supine position whilst making rapid finger movements on the rats' ventral surface as in human tickling. Research, including our own, has shown that tickled rats often produce 50 kHz ultrasonic vocalisations (USVs) believed to indicate positive affect in rats. However, there is also considerable individual variation in response to the standard tickling protocol. This suggests there is a risk that some rats may perceive tickling as a negative experience depending on how tickling is performed. Based on our research experiences of the standard tickling protocol we have developed a 'playful tickling' protocol intended to mimic more closely the dynamic nature of play. The project aim is to investigate whether playful tickling protocols give rise to more uniform increases in positive affective indicators across individuals relative to the standard tickling protocol. On this basis, we will refine a rat tickling protocol for both males and females validated against indicators of positive affect. We will also test whether this refined tickling protocol reduces variation in the biological consequences of tickling (e.g. behavioural and physiological responses to standard anxiety tests such as the plus maze), which will increase the repeatability of research where tickling is applied either as a standard enrichment or as an experimental treatment. Lastly, we will engage with researchers locally, nationally and internationally through our web-site and stakeholder group to disseminate understanding of the benefits of tickling and to encourage its wider uptake in practice and to gather data on the wider use of tickling in research and as a form of enrichment.