Plate Nº 70 · recorded September 30, 2026
Biology & EvolutionReported finding
Zoos Rarely Rearrange Collections When Species Risk Shifts
The largest study of its kind finds zoos rarely add species as their extinction risk rises, while breeding programs and visitor favorites drive collection growth.
By Nathan Brooks4 min read710 words
In brief
- Researchers analyzed 7,200+ species across 613 zoos in 72 countries over 30 years.
- Species whose extinction risk or trade restrictions increased were generally not more likely to be held by more zoos.
- Participation in managed breeding programs was the strongest predictor of growth in zoo holdings.
When a species slides closer to extinction, do zoos respond by taking it in? A new study suggests that, most of the time, they do not.
Researchers at Nottingham Trent University analyzed more than 7,200 species across 613 zoos in 72 countries over a 30-year period. It is the largest study of its kind. The team compared changes in which animals zoos held with changes in each species' conservation status, including extinction risk, international trade protections and involvement in zoo breeding programs. The research, which also involved NTU's Nottingham Business School, is published in Proceedings of the Royal Society B: Biological Sciences.
The findings point to a "conservation gap": most zoos did not consistently increase support for species as their conservation concern grew, nor reduce support when it eased.
Rising threat rarely changes holdings
Working with data from the nonprofit organization Species360, the researchers found that species which became more threatened on the IUCN Red List of Threatened Species — the global inventory of extinction risk — or gained stricter trade protections were generally not more likely to be taken up by additional zoos. The pattern ran the other way too: species that became less threatened, or had trade restrictions relaxed, were rarely phased out.
Once a species was established in a zoo's collection, that zoo tended to commit to it for the long haul.
Meanwhile, some animals gained ground for reasons far removed from extinction risk. Domestic species, pet-trade reptiles and crowd favorites such as chickens, goats, meerkats and sheep showed the strongest increases in holdings. The researchers interpret this as evidence that visitor engagement — and the funding it generates for conservation work — continues to shape collection decisions alongside formal conservation criteria.
Breeding programs are the real engine
The single largest predictor of growth in zoo holdings was participation in managed breeding programs, not changes in a species' conservation or protection status. Notably, some species with expanding breeding programs are of relatively low conservation concern.
The researchers say this highlights coordinated, community-run breeding programs as one of the zoo sector's most effective conservation tools. The sector can point to high-profile ex situ successes — conservation work outside a species' natural habitat — including the California condor, the black-footed ferret and the Arabian oryx.
Space, expertise and competing demands
The study does not accuse zoos of indifference. "What struck us wasn't a lack of commitment; it was how rarely a change in a species' conservation status on its own seemed to move the needle," said lead author Hannah Jenkins, who carried out the research as part of her Ph.D. at Nottingham Trent University.
"Species planning is a genuinely complex balancing act: zoos are weighing conservation value against space, welfare, cost and visitor engagement, often without a shared, standardized framework to guide those trade-offs," Jenkins said.
Samantha Ward, professor of zoo animal welfare and legislation in NTU's School of Animal, Rural and Environmental Sciences, spelled out the practical constraints. "Challenges for zoos globally could include limited space and expertise. There is only a certain amount of space within a zoo boundary and they must balance conservation-important species with those that bring in the visitors," she said. "Additionally, some of the rarest species can be difficult to keep and knowledge of how to house them, feed them and improve breeding may be limited."
A case for clearer frameworks
The team argues their findings make the case for more strategic and standardized species-planning frameworks, helping zoos weigh conservation value against these competing pressures explicitly and consistently across the sector. Such approaches should strengthen, rather than replace, the judgment calls zoos already make, they say.
"Our hope is that this research supports the sector with practical evidence to build clearer species-planning tools, so that as conservation needs change, zoos are even better equipped to respond," Jenkins said.
The study is observational, so it describes patterns in holdings rather than proving why individual decisions were made. Zoos also juggle genuine constraints — finite space, animal welfare, costs and uncertain expertise with rare species — that no planning framework can simply abolish. Still, the researchers suggest the results offer a practical evidence base the sector can use to sharpen its conservation impact as extinction pressures mount.
via Phys.org Biology (Source)
More from Nathan Brooks
Nearby plates
- Tracking 4,581 Animals Reveals a Hidden Human Effect on Wildlife
- Marmots Get an OnlyFans as US Science Funding Cuts Bite
- Scientists Raise Alarm Over £162m Research Funding Cuts
- Largest-Ever Jaguar Study Maps How Populations Connect Across Americas
- Animals May Have Evolved 200 Million Years Earlier Than Thought