Do conservation priorities predict changes in zoo species holdings? A 30-year global analysis

Zoos increasingly position themselves as conservation organizations, yet it remains unclear whether their species-planning decisions reflect recognized conservation priorities. This is the first global, species‑level assessment of whether changes in species status across three major criteria (IUCN Red List, CITES appendix listings and ex situ management programmes) affect zoo collections. Using historical holdings data from 613 zoological institutions (1990-2021) combined with conservation datasets, we evaluated trends in the number of institutions holding 7240 tetrapod species. Linear models quantified species-specific trajectories to determine whether shifts in conservation status were associated with predictable changes in holder numbers. Most species did not show changes in holders following a change in criteria. Species that were up-listed to higher conservation concern did not consistently increase in holders, and down-listed species were rarely phased out. Ex situ management programmes showed the strongest association with positive trends, yet these programmes often included species with non-conservation roles. This study suggests that while zoos increasingly position themselves as conservation-focused institutions, their species-planning decisions do not consistently align with changes in formal conservation criteria, highlighting a gap between conservation prioritization and real-world ex situ decisions. Standardization of institutional species-planning and evaluation can benefit zoo decision-making and strengthen contributions to conservation.