What does endangered mean for an animal?

On the IUCN Red List, an endangered species is one facing a very high risk of extinction in the wild, based on measurable evidence such as a steep population decline, a very small population, or a very small and shrinking range.

What is the difference between endangered and critically endangered?

Both are threatened categories on the IUCN Red List. Critically Endangered means an extremely high risk of extinction in the wild, the most severe category before Extinct in the Wild. Endangered means a very high risk. The thresholds for Critically Endangered are stricter, for example fewer than 250 mature individuals instead of fewer than 2,500 under one of the criteria.

Is 'endangered' on the IUCN Red List the same as under the Endangered Species Act?

No. The IUCN Red List is a global scientific assessment. The U.S. Endangered Species Act is a law with its own 'endangered' and 'threatened' listings, decided by U.S. agencies. A species can be listed under one and not the other, or in different categories.

Can you see endangered animals at zoos?

Yes. Many accredited zoos keep endangered species as part of cooperative breeding programs, such as AZA Species Survival Plans, that maintain healthy backup populations and sometimes return animals to the wild.

Conservation status

Endangered

Also called EN, IUCN Endangered

Definition

Endangered (EN) is an IUCN Red List category for species facing a very high risk of extinction in the wild. It is the middle of the three 'threatened' categories, above Vulnerable and below Critically Endangered.

On this page

Definition
What "Endangered" means
How a species qualifies
Endangered vs. the Endangered Species Act
Why it matters at the zoo
Animals in this category
Common questions

What "Endangered" means

Endangered is one of the categories on the IUCN Red List of Threatened Species, the most widely used global assessment of extinction risk. It's run by the International Union for Conservation of Nature (IUCN).

A species is listed as Endangered when the evidence shows it faces a very high risk of extinction in the wild. Endangered sits in the middle of the three "threatened" categories:

Vulnerable: high risk
Endangered: very high risk
Critically Endangered: extremely high risk

Its official abbreviation is EN.

How a species qualifies

The IUCN doesn't use opinion or popularity. A species is assessed against five sets of measurable criteria, and it qualifies as Endangered if it meets any one of them. In simplified form:

A: Rapid decline. The population has fallen, or is expected to fall, by 50% to 70% or more over 10 years or three generations, whichever is longer.
B: Small, shrinking range. The species lives in a very small area (an extent of occurrence under 5,000 km², or an area of occupancy under 500 km²) that is fragmented or declining.
C: Small, declining population. Fewer than 2,500 mature individuals, and still declining.
D: Very small population. Fewer than 250 mature individuals.
E: Modeling. Analysis shows at least a 20% chance of extinction in the wild within 20 years or five generations.

Experts review the evidence, and assessments are updated as new data comes in. A species can move up or down the scale over time.

Endangered vs. the Endangered Species Act

The word "endangered" means two different things in the U.S.:

On the IUCN Red List, it's a global scientific category.
Under the Endangered Species Act, it's a legal listing made by U.S. agencies that triggers legal protections.

The two are decided separately, so a species can be "endangered" under one and not the other. On Feather & Fang, animal pages show the IUCN Red List category.

Why it matters at the zoo

Many species you can see in U.S. zoos are Endangered in the wild. Accredited zoos often manage these animals through Species Survival Plans, cooperative breeding programs that keep a healthy, genetically diverse population in human care. Some of those programs also support conservation in the wild or return animals to their native habitat.

Endangered animals you can see in U.S. zoos

Ring-tailed Lemur

Lemur catta

Red panda

Ailurus fulgens

African Spurred Tortoise

Centrochelys sulcata

Black-handed Spider Monkey

Ateles geoffroyi

Chinchilla

Chinchilla lanigera

Reticulated giraffe

Giraffa reticulata

Tiger

Panthera tigris

Komodo Dragon

Varanus komodoensis

Amur tiger

Panthera tigris

Grey Crowned Crane

Balearica regulorum

African Wild Dog

Lycaon pictus

Siamang

Symphalangus syndactylus

See all endangered animals in U.S. zoos →

Common questions

What does endangered mean for an animal?
On the IUCN Red List, an endangered species is one facing a very high risk of extinction in the wild, based on measurable evidence such as a steep population decline, a very small population, or a very small and shrinking range.
What is the difference between endangered and critically endangered?
Both are threatened categories on the IUCN Red List. Critically Endangered means an extremely high risk of extinction in the wild, the most severe category before Extinct in the Wild. Endangered means a very high risk. The thresholds for Critically Endangered are stricter, for example fewer than 250 mature individuals instead of fewer than 2,500 under one of the criteria.
Is 'endangered' on the IUCN Red List the same as under the Endangered Species Act?
No. The IUCN Red List is a global scientific assessment. The U.S. Endangered Species Act is a law with its own 'endangered' and 'threatened' listings, decided by U.S. agencies. A species can be listed under one and not the other, or in different categories.
Can you see endangered animals at zoos?
Yes. Many accredited zoos keep endangered species as part of cooperative breeding programs, such as AZA Species Survival Plans, that maintain healthy backup populations and sometimes return animals to the wild.

Sources

Last reviewed October 5, 2026

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