Liz Bonnin presents a provocative episode of Horizon investigating how new scientific research is raising hard questions about zoos – the film explores how and why zoos keep animals, and ultimately whether they need to change to keep up with modern science, or ultimately be consigned to history. Zoos have tried to rebrand themselves as centres of research, conservation and education, but to what extent do they achieve these aims? With contemporary understanding about the complexity of animal behaviour, and the fact that most of us can see animals up close and in high definition in their natural environment on television, Horizon asks, in the 21st century, can we really justify keeping animals in zoos?