A 30-year global study examines whether changes in conservation priorities are reflected in the species zoos keep.

Zoos frequently describe conservation as central to their purpose. That commitment raises a reasonable question: when a species becomes more threatened, do decisions about which animals to keep change with it?

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A study published in Proceedings of the Royal Society B on September 30, 2026 examined this relationship across 613 zoological institutions in 72 countries. Using records covering 1990–2021, researchers analysed 7,240 species of mammals, birds, reptiles and amphibians. Their findings suggest that changes in recognized conservation criteria did not consistently correspond with changes in how widely species were held.

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What Did the Researchers Measure?

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The researchers combined historical Species360 records with IUCN Red List assessments, CITES listings and managed program records from AZA, EAZA and WAZA. They tracked the number of institutions holding each species, examining trends following changes in those criteria.

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This distinction matters: the analysis counted holding institutions. It did not directly measure habitat protection, wild population recovery, animal welfare or the full conservation contribution of each zoo.

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The sample also consisted of institutions with continuous collections throughout the study period. It represents a substantial international dataset, rather than every zoo worldwide.

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Greater Conservation Concern Did Not Consistently Bring Broader Support

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Species moving into threatened IUCN categories did not consistently gain more holding institutions. More restrictive CITES listings likewise did not produce a uniform expansion in holdings. Species whose conservation concern or trade restrictions decreased were generally not systematically phased out.

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Many trends were classified as neutral. In this study, that meant a change of less than one holding institution per year; it did not necessarily mean that nothing changed.

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The central finding is therefore about the absence of a consistent response across the sampled institutions. It does not mean that no threatened species received additional support.

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A Breeding Program Does Not Automatically Equate to Conservation

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Managed programs showed a clearer relationship with changes in holdings than IUCN or CITES changes did. However, the authors explain that such programs serve several purposes. These can include maintaining captive populations, education, exhibit value, research and developing husbandry expertise.

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A program's existence alone consequently cannot establish its conservation benefit. Understanding its contribution requires knowing its objectives, activities and outcomes.

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This is a useful distinction for visitors evaluating conservation claims. Maintaining a population in human care may support a defined conservation strategy, but the connection should be explained rather than assumed.

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Visitor Appeal and Finite Space

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The authors identified domestic animals, reptiles popular in the pet trade and charismatic zoo favourites among the species with the strongest increases in holding institutions. They interpret these patterns as consistent with visitor-oriented considerations influencing species choices. The holdings data do not establish the motivation behind every individual decision.

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The paper also describes uneven representation in managed programs and competition for limited space. Mammals were more widely represented in programs than amphibians in the dataset. This raises questions about how resources are allocated across different animal groups.

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Popular species can contribute indirectly by attracting visitors and helping generate conservation funding. That possibility deserves consideration alongside a clear account of the benefits actually delivered.

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Conservation Planning Must Also Account for Welfare

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A species becoming more threatened does not automatically mean that more zoos should acquire it. Suitability for captivity, husbandry expertise, disease risks, social relationships, available space and the needs of existing animals all matter.

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Similarly, a species becoming less threatened is not a reason to disrupt an animal's care or dismantle a program that remains necessary. Maintaining progress may require continued support.

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The authors acknowledge successful conservation programs and emphasize that competing financial, biological, welfare and operational pressures can help explain the observed patterns. They do not interpret those patterns as proof of a deliberate disregard for conservation.

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A Conservation Commitment Should Be Open to Evaluation

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The study supports more integrated, transparent species planning. Institutions should explain why they keep and breed particular species, how those decisions relate to conservation objectives, and how success is evaluated.

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For the public, the useful questions are practical: what is this program intended to achieve, how does it benefit wildlife, and what evidence shows that benefit?

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Conservation claims deserve clear purposes and demonstrable outcomes.

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Source:

Jenkins H, Welton R, James C, Ward SJ. (2026). Do conservation priorities predict changes in zoo species holdings? A 30-year global analysis.
Proceedings of the Royal Society B, 293: 20260380.

Related Reading:

Conservation or Collection? What Determines Which Animals Live at the Zoo?

A complementary scientific analysis examining how conservation priorities, threatened-species status, and institutional collection planning influence which animals zoos maintain—and whether those choices translate into measurable benefits for wildlife.
 

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