Critically Endangered Animals

Critically endangered species are at a very high risk of becoming extinct in the wild or extinct. For an animal to be added to the category, it must meet any of the following criteria regarding population or habitat decline:

• Rapid Population Reduction

  • A taxon's population size is reduced by 90 percent or more over 10 years or three generations, whichever is longer, and the reduction causes are understood, reversible, and have stopped. For example, let's pretend there's a bird species that traditionally had a population of 2000. Over 10 years, it drops to 200 because a logging company demolished its habitat. If laws are put in place that bar the logging company from continuing to fell trees in the habitat, then the IUCN will list it as "critically endangered" because the reason for the decline is understood and ceased.
  • A taxon's population size is reduced by 80 percent or more over 10 years or three generations, whichever is longer, but the reduction cause may not be understood or reversible. For example, let's say there's a bird species that traditionally had a population size of 2000. Over 10 years, it drops to 400. However, scientists can't figure out why they're dying off. In this case, the IUCN would list it as "critically endangered" because the decimation is evident, but scientists can't figure out why.
  • A taxon's population size is reduced by 80 percent or more over 10 years or three generations, whichever is longer, and the animal is also battling habitat shrinkage or another threat.

• Geographic Reduction

  The area where a species can live is reduced to 100 square kilometers or less, or the area that the species currently and actually occupies is reduced to 10 square kilometers, and at least two of the following criteria are also met:

  • The population is known to exist in only one location.
  • Scientists observe or predict that the habitat will continue to shrink or be degraded, and there's also a decline in subpopulations or the number of reproducing adults.
  • Scientists observe extreme fluctuations in the number of locations, subpopulations, or the number of reproducing adults.

• Dangerously Low Number of Adults

  • A taxon's population only has 250 or fewer adults left, and a 25 percent decline is anticipated within three years or one generation, whichever is longer. If none of the taxon's subpopulations contain more than 50 adults, or 90 percent of the species' adults live in one subpopulation, it will qualify as critically endangered.
  • Scientists observe extreme fluctuations in the number of mature adults in a given population.

• Dangerously Low Overall Population Size

  • Only 50 or fewer individuals of a taxon remain.

• Expected Rapid Decline

  • Research and studies indicate that there's a 50 percent or greater chance that the taxon will be extinct in the wild within 10 years or three generations, whichever is longer.

How many species are currently critically endangered?

In the latest iteration of the list, 3,947 taxons — aka scientifically accepted units of species — are classified in the critically endangered category.