CONSERVATION OR COLLECTION? WHAT DETERMINES WHICH ANIMALS LIVE AT THE ZOO?

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A new study offers a revealing look at conservation, collection planning and visitor appeal.

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Modern zoos increasingly describe conservation as one of their defining purposes. But there is another way to examine that claim. Instead of asking what a zoo says about conservation, we can ask: What animals does it actually choose to keep?
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A new peer-reviewed study published in PLOS ONE examined the vertebrate collections of 113 institutions belonging to the British and Irish Association of Zoos and Aquariums (BIAZA), representing approximately 92% of the association’s membership. The researchers documented 106,240 individual animals representing 2,629 species.
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What they found provides an unusually revealing look at the relationship between conservation priorities, zoo collection planning and the realities of operating a visitor-supported institution.
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CONSERVATION AND COLLECTION PLANNING ARE NOT NECESSARILY THE SAME THING:

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If conservation were the primary factor determining which animals zoos maintain, we might expect threatened species to dominate their collections. They did not.
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The researchers found that 28.5% of the individual vertebrates were species classified by the IUCN as Vulnerable, Endangered or Critically Endangered, while 58% belonged to species classified as non-threatened—Near Threatened or Least Concern. The remaining animals included species classified as Extinct in the Wild, Data Deficient or Not Evaluated, along with domesticated animals and individuals that could not be identified to species level for the analysis.
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Those numbers require some important context. They do not mean that only 28.5% of the animals contribute to conservation. A species can be relatively secure globally while facing serious decline within a particular country or region. Animals belonging to non-threatened species may also contribute to research, education, population management or other legitimate conservation objectives.
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But the findings do challenge a simpler assumption—that the animals maintained by modern zoos necessarily reflect the wildlife most urgently requiring conservation intervention. And that leads to a much more interesting question.
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WHAT HAPPENS WHEN CONSERVATION AND VISITOR APPEAL POINT IN DIFFERENT DIRECTIONS?

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Zoos do not operate solely as conservation organizations. They are also visitor attractions. For most institutions, admission and other visitor-generated revenue help keep the gates open, employees paid, animals cared for and conservation programs funded. Popular animals can therefore play an important economic role even when those particular species are not conservation priorities.
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The difficulty is that the species most urgently requiring conservation attention are not necessarily the animals visitors are most eager to see. Amphibians provide a revealing example. They are among the world’s most threatened vertebrates, yet the researchers found amphibians had the lowest species diversity among the vertebrate groups examined.
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There can be practical reasons for this. Some species require highly specialized husbandry, environmental conditions and expertise. But the researchers also discuss another reality: small amphibians may simply lack the visitor appeal of larger, more charismatic animals.
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That does not mean zoos should stop keeping elephants, lions, giraffes or other popular species. It does mean we should recognize the tension honestly. When conservation priorities and visitor preferences point in different directions, which one ultimately determines what lives at the zoo?
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WHEN CAPTIVITY HAS A CLEAR CONSERVATION PURPOSE:

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Importantly, the study also demonstrates what zoological institutions can accomplish when captive populations are connected to identifiable conservation objectives. Global conservation status does not always tell the entire story.
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The European wildcat, for example, is classified globally as Least Concern, yet populations in Britain have experienced severe declines. Water voles and pine martens similarly demonstrate how species that may appear relatively secure at a global level can still have significant regional conservation needs. In circumstances like these, captive populations can provide animals, genetic diversity, husbandry expertise and scientific knowledge that may contribute directly to restoration programs.
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The researchers also identified six non-native species classified as Extinct in the Wild within the collections they examined. Among them is the Socorro dove, whose captive population has played a role in international efforts intended to eventually return the species to the wild.
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These are not abstract claims about conservation. They are examples of captivity being connected to an identifiable conservation purpose. And that distinction matters.
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HOW MUCH OF THE COLLECTION IS CONNECTED TO LOCAL CONSERVATION?

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Against those successes, another finding deserves consideration. Approximately 9% of the animals examined belonged to species native to the UK, while only about 2% were UK priority species.
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Those percentages alone cannot tell us whether an institution’s conservation contribution is substantial or insignificant. A relatively small captive population could be extraordinarily valuable if it provides genetically important animals for a recovery program. But the numbers raise a legitimate question about priorities.
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Zoos possess facilities, animal-care expertise, veterinary knowledge, reproductive experience and—in many cases—considerable public influence. As biodiversity declines, decisions about how those resources are allocated become increasingly consequential.
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The question therefore isn’t simply how many animals a zoo keeps. It is why those particular animals are there.
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CONSERVATION HAS TO COEXIST WITH ECONOMICS:

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Perhaps one of the most useful aspects of this research is that it does not pretend zoos operate outside economic reality. Zoos need visitors, and visitors are often drawn to charismatic animals. Those animals can generate revenue that helps support conservation work involving species the average visitor may never have heard of.
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That relationship makes the issue considerably more complicated than saying that zoos either are—or are not—conservation organizations. Conservation and entertainment can coexist. Education and recreation can coexist. A popular animal can help finance conservation of a far less popular one.
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But acknowledging those relationships also means acknowledging that keeping an animal at a zoo and conserving wildlife are not automatically the same thing. That distinction becomes particularly important when conservation is presented to the public as a defining justification for maintaining wild animals in captivity.
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PERHAPS WE SHOULD MEASURE CONSERVATION DIFFERENTLY:

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Simply counting endangered species tells us something. It does not tell us everything. A zoo could maintain many threatened animals without producing meaningful conservation outcomes. Another institution might maintain relatively few threatened species while contributing substantial funding, research, expertise or animals to successful recovery programs.
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Perhaps a better evaluation would examine not merely the conservation status of the animals behind the exhibits, but the resources and outcomes connected to them. How much institutional funding and staff expertise are directed toward wildlife conservation? Are captive breeding programs connected to realistic recovery objectives? Does research involving captive animals produce knowledge that benefits wild populations? Are facilities and expertise being used for species facing significant conservation challenges, including those within the institution’s own region?
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Ultimately, all of those questions lead to one that may matter most:
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What happened in the wild because the zoo was involved?
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That moves conservation beyond mission statements and marketing language. It asks us to look for outcomes.
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THE QUESTION IS NOT WHETHER ZOOS CAN CONSERVE WILDLIFE

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They clearly can. Captive populations have helped prevent extinctions, restore wild populations, advance veterinary and reproductive science and expand our understanding of species biology. This study contains examples of exactly that.
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The more difficult question is whether conservation consistently determines which animals zoological institutions choose to keep, how those animals are managed and what purpose their captivity ultimately serves. The researchers found that globally non-threatened animals substantially outnumbered threatened animals in the collections they examined, while locally prioritized wildlife represented only a small proportion of the overall population.
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That doesn’t invalidate zoo conservation. It makes examining it more important.
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Because if conservation is going to be presented as a defining purpose of the modern zoo, perhaps the most meaningful question isn’t:
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Does this zoo have endangered animals?
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It is:
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WHAT CONSERVATION PURPOSE DOES KEEPING THIS ANIMAL SERVE?

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Sometimes there will be a compelling answer. The animal may be part of a carefully managed assurance population. Its offspring may eventually contribute to reintroduction. Research involving the species may help protect its counterparts in the wild. Its presence may generate funding or public support for conservation far beyond the zoo itself.
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Those contributions deserve recognition. But when the connection between keeping an animal and conserving wildlife becomes difficult to identify, asking the question remains important.
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Because ultimately, conservation should be measured not simply by what lives inside the zoo—but by what changes for wildlife outside of it.
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Source: Lennon, J.J., Pernetta, A.P., White, R.L. & Crooks, N. (2026). Taking stock: Can captive species contribute to biodiversity conservation? PLOS ONE, 21(8), e0354602.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0354602
 

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