The model
Smithsonian's National Zoo and Conservation Biology Institute
Founded by Congress in 1889 "for the advancement of science and the instruction and recreation of the people," the National Zoo in Washington runs on two campuses: the public zoo in Rock Creek Park and a breeding and research campus at Front Royal, Virginia. The model joins four jobs in one place: animal care, field conservation, science and teaching. Its scientists bred and returned golden lion tamarins to Brazil from 1984, helped bring back the black-footed ferret, and worked on returning the scimitar-horned oryx to Chad from 2016. Giant pandas returned to Washington in October 2024.
The standard
AZA accreditation
The Association of Zoos and Aquariums accredits member zoos after a written application and an on-site inspection by a team that includes a veterinarian, an animal-care expert and an operations expert. Accreditation lasts five years and covers animal welfare, veterinary care, conservation, education, safety and finances. Fewer than one in ten animal exhibitors licensed by the US Department of Agriculture are AZA-accredited (check the current figure).
Welfare science
The Five Domains
Older rules listed "Five Freedoms" (the Brambell Report, UK, 1965): freedom from hunger, discomfort, pain, fear and the freedom to behave normally. The Five Domains model (David Mellor and Cam Reid, 1994; updated 2020) asks keepers to look at four outside domains, nutrition, physical environment, health and behavioral interactions, and to judge the fifth, the animal's mental state, from them. The aim moved from preventing suffering to giving animals good days: choices, challenge and comfort.
Every day
Enrichment
Enrichment means changing an animal's world so it can use its natural skills: puzzle feeders for chimpanzees, ice blocks with fish for polar bears, scent trails for big cats, browse hung high for giraffes, deep sand for meerkats. Good programs set a goal, try an item, record what the animal did and keep what works. The test is behavior: more foraging and exploring, less pacing.
Choosing parents
Conservation breeding
Zoos keep studbooks, the family tree of every animal of a species in human care, and plan pairings to keep genetic diversity high. AZA calls its breeding and management plans Species Survival Plans (SSPs). SAFE (Saving Animals From Extinction, launched 2015) adds field work and fundraising for selected species, among them the African lion, gorilla, giraffe, chimpanzee, red panda, sloth bear, orangutan and Asian hornbills.
Back to the wild
Reintroduction
Some species exist today because zoos bred them when the wild ones were gone: the Arabian oryx (extinct in the wild by 1972, returned to Oman from 1982), the California condor (all 27 survivors taken into care in 1987), the black-footed ferret and the golden lion tamarin. Reintroduction is slow and costly and works only when the threat that caused the loss has been dealt with.
Science
Research
Zoo animals let scientists study what is hard to see in the wild: reproduction, nutrition, disease, hearing and thinking. Zoo work built the hormone tests now used to time breeding in elephants and pandas, and zoo veterinarians help track diseases that pass between wildlife, livestock and people.
Teaching
Education
Most people meet a living elephant or gorilla only at a zoo. Good zoo teaching moves from "look at that" to "what is it doing, and why," and from feeling to action: buying certified palm oil, sustainable seafood, or keeping cats indoors. Researchers still debate how much a single visit changes what people know and do.
11 species, read live from the catalog. Program names checked against published zoo lists (November 2026).