Species Survival Statistics

The Association of Zoos and Aquariums (AZA) and its member institutions (AZA-accredited institutions, Certified Related Facilities, and Conservation Partners) must frequently answer the question “How long does this species live?”  Until the creation of the Species Survival Statistics Library (previously behind AZA member paywall), no science-based reference source has existed to allow the zoo community to consistently and easily communicate appropriate survival-related information on zoo and aquarium animals to the public.  Using consistent language and scientific facts when discussing this topic will reduce uncertainty and eliminate contradictions. Scientists at Lincoln Park Zoo and the AZA Population Management Center (PMC), with support from the Columbus Zoo and Aquarium, have created a reference library of scientifically-valid median life expectancies based on studbook datasets for many species in AZA-accredited zoos and aquariums. AZA recommends all members utilize the Median Life Expectancy as the primary referenced statistic for a species’ typical lifespan, and use this Library as the primary reference for those median life expectancies.

Median life expectancy is the appropriate way to communicate about how long a typical individual of a given species lives. For context, the median life expectancy from age one for humans in the U.S. is 77.5 years and the maximum longevity (documented worldwide) is 122 years. This means that assuming that we live to our first birthday, about half of the human population will die before 77 and half will die after.  Very few people can expect to reach 122.  If we discuss the age of a particular individual in relation to the maximum longevity, it could cause confusion because very few individuals live that long.  For example, a person that lived to age 82, well exceeding the median life expectancy, should not be characterized as having died young for failing to reach 122, the maximum longevity.

Please read the Frequently Asked Questions/How To Guide for more details on how to interpret the table of median life expectancies, which is available below, and the full Survival Statistic reports, 4-5 page reports that give more details on the statistics calculated for each species. AZA-accredited institutions may request these reports by e-mailing conservation@aza.org.  If this is an emergency outside of normal business hours, contact Rob Vernon (rvernon@aza.org), Senior Vice President, Communications and Marketing.  If there are any questions, please submit them to conservation@aza.org.

Download the Survival Statistics Table

Make sure to check back quarterly to download an up-to-date table. There are hundreds of species with Survival Statistics Reports calculated to date, and more species will be added in the future. See the FAQs for more details.

The table summarizes the Median Life Expectancy (MLE) for all populations that have been analyzed. For each species, it reports either:

  1. sex-specific MLEs - male and female statistics are reported separately if there are very different survival patterns between the sexes,
  2. a single MLE – if male and female survival patterns are not different, data are pooled to increase sample size and a single value is reported, or
  3. "can’t be calculated" – if an entire dataset (both sexes) or a subset of data (one sex only) fails a set of data quality tests, we cannot report an accurate MLE and this is indicated.

See the full Survival Statistics reports for more details for each species. You can request a full Descriptive Survival Statistics report for any species in the table by contacting conservation@aza.org.


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