The impact of fluid restriction protocols on Rhesus macaques (Macaca mulatta) and refinements to their use

Abstract

Animal models are an integral component of modern science. Non-human primates (NHPs) are effective models for many human diseases and conditions due to their close phylogenetic relationship. In particular, their specific cortical organisation and neural specialisations makes them invaluable for neuroscience research, both basic and applied. The advanced cognitive abilities of NHPs and their fine motor dexterity means that they can be trained to perform complex tasks in the laboratory whilst cortical activity is measured. Many of these tasks require hundreds or thousands of iterations in order to achieve statistical power to adequately test hypotheses, and consequently, the monkeys need to be sufficiently motivated to perform. One way in which researchers motivate their monkeys is through the use of fluid restriction protocols. By limiting the free intake of fluids, fluid rewards can be used as a primary motivator for the monkeys to continue to perform the tasks. These restriction protocols, although widely used, remain controversial due to their potential negative impacts on animal welfare. The aim of my thesis was to explore the impacts of fluid restriction protocols on rhesus macaque (Macaca mulatta) behaviour and physiology and to investigate possible refinements to their use. My experiments found no evidence of negative physiological impacts of fluid restriction protocols and only limited impact on behaviours, alleviating some of the concerns surrounding these procedures. I also assessed the use of preferred fluids and social stimuli (photographs and video clips of conspecifics) as rewards. Mixed results were gained when assessing fluid preferences and again when implementing the preferences into laboratory tasks. Preferences for social stimuli were established for all animals tested, but these did not translate into motivating rewards on a trial-by-trial basis. These studies have tackled important scientific and ethical issues surrounding the use of rhesus macaques in behavioural neuroscience. The outcomes are discussed in a wider context and the potential applications to laboratory practice are evaluated.