The voice of choice: A scoping review of choice-based animal welfare studies

"Choice and control" is a phrase used widely in animal welfare science to describe providing captive animals with the ability to select between possible outcomes (stimuli or events). This concept has gained traction as a pivotal management technique across a variety of captive settings; however, little has been done to quantitatively evaluate choice as a welfare-improving practice. Our goal was to use a PRISMA framework to identify and review the current empirical literature on the welfare effects of choice provisions by examining measurable behavioural and biological outcomes. We evaluated choice-based studies which used an experiment design to compare choice to non-choice conditions and the impact of choice on welfare. Covidence software was used to screen and extract data from peer-reviewed literature identified across PubMed, Web of Science Advanced, and Scopus Advanced databases. Study inclusion was contingent upon a methodology which offered options for at least two or more stimuli/events given concurrently and which also contrasted a choice condition to a non-choice condition. A total of 13 papers were identified and included in this review. The majority of the papers included choices associated with enclosure access, food, and enrichment devices which resulted in improved behavioral and physiological welfare indicators across zoological, agricultural, and research laboratory settings. However, the presence of a couple papers reporting unclear or neutral impacts highlighted the need for further empirical research into the welfare impacts of choice. Increased experimental examinations with a wider range of captive settings and species are discussed and considered necessary to better comprehend the welfare benefits of providing increased choice opportunities for captive animals.