GAPs in the study of zoo and wild animal welfare.

To investigate the science of animal welfare for zoo and wild animals in the period from 1966 to 2007, we conducted a bibliometric analysis of abstracts downloaded from The Web of Science((c)) database using the keyword combination "Animal welfare, Zoo* and wild" in the topic field. In total we downloaded 1,125 abstracts, which were classified into the following categories: year of publication; environment of the study (e.g.