Using sighting records to infer extinction

Extinction, the disappearance of the last individual of a species, is rarely observed, is very difficult to detect and therefore usually must be inferred. And getting it right is important. Listing a species as extant (still in existence) when it is actually extinct is undesirable since it can lead to misallocation of funds, incorrect reporting of current extinction rates and loss of public credibility in conservation science (see Decision Point #38, p6-9 for background on the importance of this decision).

Working out whether a species is extinct or not can be hard because small populations can go undetected and often there’s not much data available. However, there are many statistical methods you can use to assess extinction from scarce data. Unfortunately, choosing between these methods can be confusing.

Elizabeth Boakes and colleagues have recently reviewed the different methods that are available. They have explained their assumptions and data requirements, and the situations in which each should be used. They have also used examples from the literature to illustrate the choices they recommend. It’s basically a manual for using statistical methods to infer extinction.

So, now there’s no excuse for not having a quantitative measure of the likelihood of extinction. A win for transparent decision making!


Boakes E, Rout T and Collen B (2015). Methods in Ecology and Evolution.

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