The zoo scientific community was among the first to focus attention on captivity induced stereotypic behaviors, their causes, and methods of eradication. Environmental enrichment has emerged recently as the main husbandry tool for tackling this problem. An increasing number of research publications have attempted to evaluate the effectiveness of enrichment in reducing stereotypic behavior and to develop further concepts to explain how effective enrichment works. A review and meta-analysis of this literature indicates that enrichment is a successful technique for reducing stereotypic behavior in zoo animals. Enrichment was associated with significant reduction in stereotypy performance about 53% of the time. Published enrichment and stereotypy research is lacking for most zoo species, with most studies on large, charismatic, and often endangered species, but it is unclear whether stereotypies are more prevalent in these species. In addition, problems with scientific methods and data presentation, quantitatively detailed in this work, severely limit the conclusions drawn from zoo research. Further understanding of what kinds of enrichment works and what doesn’t will require greater attention to experimental design, sample size, statistical analysis, and better descriptions of enrichment properties and the form of stereotypy. We recommend that future studies focus on increasing sample size (e.g., through multi-institutional studies), appropriate repeated measures design (e.g., with multiple baseline and experimental phases), providing full statistical information about the behavioral changes observed (including standard error), and ultimately the development of a predictive science for enrichment, stereotypies, and wellbeing.
