A zoo is a place where wild animals are kept in enclosures so that people can see them. Modern zoos say they do much more than put animals on show: they breed endangered species, fund conservation in the wild and teach visitors about nature. The debate is whether those goals justify keeping wild animals captive at all.
People have kept wild animals for display for thousands of years, but the public zoo as we know it is fairly new. The first zoo in the United States, the Philadelphia Zoo, opened on July 1, 1874.5
Zoos are still hugely popular. A 2011 study estimated that more than 700 million people visit zoos and aquariums worldwide each year, and that the zoo and aquarium community spends about US$350 million a year on wildlife conservation.4 The Association of Zoos and Aquariums (AZA) now accredits 255 zoos, aquariums and related facilities in 12 countries. They reported more than 209 million visitors in 2024 and $372.4 million spent on field conservation in 2025.1
Supporters point to a growing extinction crisis. In July 2026, the IUCN Red List included 175,909 species, of which 49,505 were threatened with extinction.2 A 2020 study estimated that conservation action had prevented 21 to 32 bird and 7 to 16 mammal extinctions since 1993, with captive breeding playing a part for species such as the California condor and Przewalski's horse.3 Yet zoos hold only about one in seven threatened land vertebrates.30
Critics focus on the animals' lives. Happy, an Asian elephant, arrived at New York's Bronx Zoo in 1977 and lived apart from other elephants after her last partner died in 2006. In 2005 she became famous for recognising herself in a mirror, a sign of self-awareness.19 In 2022, New York's highest court ruled 5 to 2 that she was not a “person” who could be freed through habeas corpus. One of the dissenting judges, Jenny Rivera, wrote: “Her captivity is inherently unjust and inhumane.”18 Happy was put down in May 2026, aged 55.19
Single moments have also shaped public opinion. In 2016, the Cincinnati Zoo shot Harambe, a 17-year-old endangered western lowland gorilla, after a three-year-old boy crawled through a barrier and fell about 4.5 metres into his enclosure. The zoo's director, Thane Maynard, defended the decision: “You're talking about an animal that's over 400lb and is extremely strong.”6 In 2014, Copenhagen Zoo killed Marius, a healthy two-year-old giraffe, to prevent inbreeding, then fed him to lions as visitors watched.21
Much of the argument is about which zoos we mean. The US has about 3,000 roadside zoos that hold federal licences but no AZA accreditation.24 In 2022, the Big Cat Public Safety Act banned most private ownership and breeding of big cats, while exempting accredited zoos.7 In the European Union, every zoo must by law be licensed, inspected and take part in conservation.26 Some want to reform zoos and close the worst; the animal charity Born Free wants all of them “phased out.”23
Key terms
Captive breeding
Breeding animals in zoos or breeding centres, often to build up numbers of a rare species.
Ex situ conservation
Protecting a species outside its natural home, for example in a zoo or seed bank.
Reintroduction
Releasing animals, often bred in captivity, into an area where their species used to live.
Extinct in the wild
A species that survives only in captivity, with no wild population left.
Accreditation
Approval by an independent body, such as the AZA, that a zoo meets its standards for animal care and conservation.
Stereotypic behaviour
Repeated movements with no clear purpose, such as pacing or swaying, often seen as a sign of stress in captive animals.
Enrichment
Changes to an animal's enclosure or routine, such as puzzles or new smells, that give it more natural things to do.
Habeas corpus
A legal demand that a court decide whether someone is being held lawfully. Animal rights lawyers have tried to use it to free zoo animals.
Pros and cons at a glance
Pro: zoos should exist
Con: phase them out
Pro arguments
Con arguments
Key clashes
Most zoo debates are won or lost on these four questions.
1Do zoos really save species?
Both sides agree on the success stories. They disagree on how much they prove.
Pro saysThe California condor and the black-footed ferret would probably be gone without captive breeding in zoos.811
Con saysThose are rare cases. Zoos hold only about one in seven threatened land vertebrates, and most zoo animals are not endangered at all.30
2Can captivity be a good life?
The answer seems to depend on the species.
Pro saysIn more than 80% of mammal species studied, animals live longer in zoos than in the wild.15
Con saysFor big, wide-ranging animals such as elephants and polar bears, captivity brings stress, pacing and shorter lives.1617
3Do visitors actually learn anything?
Education is one of the main reasons zoos give for existing.
Pro saysA study of 5,661 visitors in 19 countries found that understanding of biodiversity rose after a zoo visit.12
Con saysThe gains were small, and an earlier AZA study only asked visitors whether they had learned something, without testing them.14
4Reform or abolish?
Even critics of zoos disagree about what should replace them.
Pro saysThe problem is bad zoos. Tough licensing and laws like the Big Cat Public Safety Act can close them while keeping the good ones.726
Con saysBetter rules cannot fix an idea that critics such as Born Free call “outdated and flawed.”23
Around the world
The US: AZA-accredited zoos sit alongside about 3,000 roadside zoos that only need a federal licence.124 Courts in New York and Colorado have both refused to treat zoo elephants as legal “persons.”19
The European Union: Under a 1999 law, every zoo in the EU must hold a licence, take part in conservation, educate the public and give animals species-specific enrichment, or face closure.26
Latin America: In 2015 a judge in Buenos Aires, Argentina, declared Sandra the orangutan a “non-human person,” and the city's zoo closed in 2016.20 Costa Rica announced in 2013 that it would close its two state-run zoos; a court delayed the plan for ten years.2728
Debate tip: comparing countries is useful evidence on both sides. Pro can use the EU to show that strong rules can raise standards; Con can use Costa Rica and Argentina to show that a country can choose to move away from zoos.
Discussion questions
For class or club discussion. There are no right answers; ask for reasons and evidence.
Should zoos exist? Explain your answer using at least one argument from each side.
Is it fair to keep one animal in captivity for its whole life if that helps save its species?
Should some animals, such as elephants or great apes, never be kept in zoos, even if other animals can be?
If you could learn the same things from a documentary or a virtual reality tour, would zoos still be worth visiting?
Should a zoo ever be allowed to kill a healthy animal? Who should decide?
Sources
Association of Zoos and Aquariums, “Zoo and Aquarium Statistics,” updated September 2026. LinkAccrediting body
International Union for Conservation of Nature, “From desert frog to deep-sea molluscs, remarkable species at risk: IUCN Red List,” press release, July 9, 2026. LinkInternational body
F. C. Bolam et al., “How many bird and mammal extinctions has recent conservation action prevented?” Conservation Letters 14(1), 2021 (online 2020). LinkPeer-reviewed study
M. Gusset and G. Dick, “The global reach of zoos and aquariums in visitor numbers and conservation expenditures,” Zoo Biology 30, 2011. LinkPeer-reviewed study
Philadelphia Zoo, “150th Anniversary.” LinkZoo history page
“Gorilla killing in US zoo to save boy sparks outrage,” Al Jazeera, May 30, 2016. LinkNews report
“Biden signs Big Cat Public Safety Act into law; ending breeding, sale and possession of certain big cats,” KWTX, December 20, 2022. LinkNews report
US National Park Service, Grand Canyon National Park, “Condor Reintroduction and Recovery,” updated February 2016. LinkGovernment agency
“Species Behind Unicorn Legend Back from Brink of Extinction, IUCN Says,” Yale Environment 360, June 16, 2011. LinkEnvironmental news
Smithsonian's National Zoo and Conservation Biology Institute, “Przewalski's horse.” LinkResearch institute
Smithsonian's National Zoo and Conservation Biology Institute, “Black-Footed Ferrets: Top Milestones for a Species Once Presumed Extinct.” LinkResearch institute
A. Moss, E. Jensen and M. Gusset, “Evaluating the contribution of zoos and aquariums to Aichi Biodiversity Target 1,” Conservation Biology 29(2), 2015. LinkPeer-reviewed study
University of Warwick, “Largest international study of zoo and aquarium visitors,” press release. LinkUniversity press release
“Of Note” (on Lori Marino's critique of the AZA visitor study), Emory Magazine, Summer 2010. LinkUniversity magazine
University of Zurich, “Greater Life Expectancy in Zoos,” November 2016, on Tidière et al., Scientific Reports, 2016. LinkUniversity report on study
University of Oxford, “Zoo life problematic for wide-ranging carnivores” (Clubb and Mason, Nature, October 2003), via ScienceDaily, October 2, 2003. LinkUniversity report on study
“Wild Elephants Live Longer Than Their Zoo Counterparts,” National Geographic, December 11, 2008. LinkNews report
Associated Press, “Top state court rejects effort to free Bronx Zoo elephant,” via KSAT, June 14, 2022. LinkNews report
Associated Press, “Happy, who taught researchers that elephants can recognize themselves, is euthanized at Bronx Zoo,” via WTOP, May 2026. LinkNews report
Associated Press, “Argentine orangutan Sandra to head to US great ape sanctuary,” via KSL.com, 2019. LinkNews report
“Copenhagen Zoo kills healthy giraffe, sparking controversy,” The Christian Science Monitor, February 9, 2014. LinkNews report
Barbara J. King, “Why Do European Zoos Kill Healthy Animals?” NPR, October 14, 2015. LinkCommentary
Born Free Foundation, “Zoos and aquaria FAQs.” LinkAdvocacy group
Rachel Fobar, “Roadside zoo elephants suffered for years before dying, new records reveal,” National Geographic, July 13, 2021. LinkNews report
Tala M. DiBenedetto, “Overview of Welfare Standards for Animals Used in Zoos and Exhibition,” Animal Legal & Historical Center, Michigan State University College of Law, 2020. LinkLegal research
Council of the European Union, Council Directive 1999/22/EC of 29 March 1999 relating to the keeping of wild animals in zoos. LinkEU law
“Costa Rica Will Do Away With Caged Animals At Its Zoos,” NPR, August 5, 2013. LinkNews report
“Visiting the Costa Rica Zoo can be a Depressing Sight,” The Tico Times, May 20, 2016, with later update. LinkNews report
Associated Press, “Elephants get to retire in California,” The Spokesman-Review, December 5, 2004. LinkNews report
D. A. Conde, N. Flesness, F. Colchero, O. R. Jones and A. Scheuerlein, “Zoos Can Lead the Way with Ex Situ Conservation,” WAZA Magazine 12, 2011, summarising their study in Science 331, 2011. LinkResearch summary
Arguments marked “Evidence needed” are waiting for a source before this guide goes live.
