British zoos and aquariums hold more than 2,600 vertebrate species, yet only a small fraction of these animals are native to the United Kingdom or listed as high conservation priorities, according to a new study published in PLOS One. The analysis of 113 institutions affiliated with the British & Irish Association of Zoos and Aquariums (BIAZA) offers one of the most detailed assessments to date of how captive collections align with biodiversity conservation. The findings suggest that zoos and aquariums are preserving some threatened wildlife, but that their collections remain heavily shaped by public appeal, historical practice and the financial demands of attracting visitors.
The study, led by Justin Lennon of the University of Brighton with colleagues Aimee P. Pernetta, Rebecca L. White and Nicholas Crooks, examined both the number of species in captivity and the size of their populations. Researchers compared their findings with the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, catalogues of species native to Britain and conservation priority lists used across the United Kingdom. This approach allowed the team to distinguish between animals that are globally threatened, species that are important to British conservation and the broader collection of animals displayed or maintained by zoological institutions.
In total, the researchers recorded approximately 106,000 captive vertebrate individuals. Fish dominated the collections, accounting for around 61% of all animals and representing the greatest species diversity. Birds made up approximately 16%, mammals 15%, amphibians 5% and reptiles 4%. The strong representation of fish reflects the enormous diversity of aquatic life and the large numbers of individuals that can be maintained in aquarium systems. It also highlights a challenge in interpreting raw collection statistics: a zoo or aquarium may hold many individuals of a species, but that does not necessarily mean the species is receiving the most urgent conservation attention.
Amphibians presented the clearest mismatch between conservation need and captive representation. They were the least diverse vertebrate group in the collections, despite being the most threatened class of vertebrates globally. Amphibians face an exceptional combination of pressures, including habitat loss, pollution, climate change, invasive species and infectious diseases such as chytridiomycosis. The fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans can damage the skin of susceptible amphibians, interfering with respiration, water balance and electrolyte regulation. Captive assurance colonies can protect species from extinction while scientists develop breeding, disease-management and reintroduction strategies, but the study indicates that these efforts remain relatively limited compared with the scale of the crisis.
Across all collections, species classified by the IUCN as Vulnerable, Endangered or Critically Endangered represented 28.5% of the total number of species. However, populations of threatened species were less than half the size of those belonging to non-threatened species. This distinction is critical. Conservation breeding depends not only on whether a species is present in a collection, but also on whether enough genetically diverse individuals are maintained to support a viable population. Small captive groups can suffer from inbreeding, loss of genetic variation and demographic instability. A population may therefore appear in institutional records while remaining too small, fragmented or poorly managed to make a substantial contribution to long-term species recovery.
The study also found that only about 9% of captive species were native to Britain, while approximately 2% appeared on one or more regional conservation priority lists. The low proportion of native species is not surprising given the international role of modern zoos and aquariums. Many institutions maintain animals from ecosystems that British visitors would otherwise never encounter, and international cooperation is essential for managing species whose wild populations cross national borders. Nevertheless, the results raise questions about whether British collections are sufficiently connected to domestic conservation needs, including the recovery of threatened mammals, birds, reptiles, amphibians and fish found in the UK’s own landscapes and coastal waters.
Zoos historically developed as places of display and entertainment, but their public mission has expanded considerably. Today, accredited institutions commonly describe their work through four connected activities: education, scientific research, conservation breeding and public engagement. These goals can reinforce one another, but they can also conflict. Large, charismatic animals such as big cats, elephants, primates and penguins often attract visitors and generate revenue that supports animal care, staff, facilities and conservation projects. Yet the species most effective at drawing crowds are not always those facing the greatest extinction risk, nor are they necessarily the best candidates for captive breeding or release into the wild.
The researchers argue that BIAZA institutions are contributing to the preservation of native and priority species, even though their collections show a broader bias toward globally non-threatened animals. Captive populations can serve as genetic reservoirs, research subjects and educational tools. They may also provide expertise that can be transferred to field conservation, from veterinary medicine and reproductive biology to habitat management and disease surveillance. In some cases, coordinated breeding programmes have prevented extinction or supported reintroduction. However, such outcomes require more than displaying rare animals. They depend on carefully managed studbooks, genetic analyses, collaboration among institutions, appropriate habitat and evidence that the threats responsible for a species’ decline have been reduced in the wild.
The authors therefore suggest that British zoos and aquariums could strengthen their conservation role by increasing both the diversity and the population sizes of threatened species in their care. Future collection planning could give greater weight to extinction risk, British and regional priorities, genetic representation and the likelihood that captive management will produce measurable benefits outside the institution. This would not necessarily mean replacing popular species or abandoning the educational value of international collections. Instead, it could involve expanding specialised programmes for overlooked animals, especially amphibians and other species that receive little public attention despite severe declines. It could also mean making conservation outcomes more visible, so visitors understand how admission fees and institutional resources support work beyond the exhibits.
“Conducting this research changed my own perspective,” the authors write. They acknowledge the continuing criticism directed at zoos and aquariums, while noting that years of analysing captive collections also revealed the scale of work taking place away from public view. Modern zoological institutions, they argue, are no longer simply places where animals are displayed. They have become centres for conservation breeding, scientific research, education and international collaboration. The new findings do not settle the debate over the conservation value of captivity, but they provide a detailed benchmark for judging it. If zoos are to demonstrate that they are partners in biodiversity protection, the most important measure may be whether their collections increasingly reflect the species most at risk—and whether the animals they protect can ultimately help sustain life in the wild.
Subject of Research: The representation of threatened, native and conservation-priority vertebrate species in British zoos and aquariums.
Article Title: Taking stock: Can captive species contribute to biodiversity conservation?
News Publication Date: 19 August 2026
Web References: https://doi.org/10.1371/journal.pone.0354602
References: Lennon JJ, Pernetta AP, White RL, Crooks N (2026) Taking stock: Can captive species contribute to biodiversity conservation? PLOS One 21(8): e0354602.
Image Credits: Biljana Martinić, Unsplash, CC0
Keywords: zoos, aquariums, captive breeding, biodiversity conservation, threatened species, amphibians, IUCN Red List, conservation genetics, wildlife protection, British zoos
Tags: biodiversity conservation in zoosBritish zoos conservation focuscaptive collections of non-native specieschallenges of zoo biodiversity managementconservation funding and zoo exhibitsconservation priorities of British zooshistorical influences on zoo animal collectionsimpact of public appeal on zoo collectionsIUCN Red List threatened speciesrole of aquariums in wildlife preservationUK native species in captivityzoo species selection criteria
