Introduction to the special issue on zoo animal welfare.

In May 2008, the Chicago Zoological Society's Center for the Science of Animal Welfare (CSAW) held a two-day international workshop designed to establish and foster new connections between zoo animal welfare scientists and welfare scientists in other fields, and to take the first step toward the development of a research agenda for zoo animal welfare science. Such a research agenda by its very nature would need to be highly multi-disciplinary and collaborative. In support of this purpose this article serves as an introduction for a collection of invited papers presented at the workshop. Workshop themes included the investigation of welfare metrics currently used and in development, elucidating gaps and determining needs for zoo welfare research, and gaining a deeper understanding of the value that understanding animals in the wild can bring to zoo animal welfare. Here we discuss some of the most relevant points made at the workshop and describe the seven most salient research needs that were suggested in consensus.