What's new from the zoo? An analysis of ten years of zoo-themed research output

The modern zoo's roles command empirical enquiry to determine the effectiveness of zoos locally and globally. Ten years ago, published work identified the need for empirical research on a diverse range of species beyond charismatic zoo megafauna. We review zoo-based research published in the decade since this original recommendation. We collectively evaluate zoo-themed research papers from those working in zoos and those external to zoos but studying zoo-housed animals. By systematically searching Web of Science (c) for zoo-based research and performing inductive content analysis to code year, journal, study animal's taxonomic classification, and research aims and outputs we evaluate trends in zoo-themed research, contrasted with trends in species holding. Significantly more birds and fish are kept compared to mammals, reptiles and amphibians, but mammals are consistently the primary research focus. Whilst output generally rises, only for birds is a steady increase in publications apparent. Husbandry evaluation is a major aim/output, but papers on pure biology, cognition and health also feature. Most publications lead to "specific advancement of knowledge" including validation of methodologies. We show that: (1) trends in species holdings are unrelated to trends in publication; (2) zoo-themed research makes meaningful contributions to science; (3) zoo researchers should diversify their aim/output categories and chosen study species to close the persisting research gaps that we have identified. Finally, we discuss our findings in the context of evident species biases within research outputs across the broader fields of zoology, conservation and ecology.